JPH1022755A - Automatic gain control amplifier, reception circuit and portable telephone set using the reception circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the automatic gain control circuit for a portable telephone set whose current consumption is reduced and whose reception sensitivity is improved and to provide the reception circuit using the control circuit. SOLUTION: The circuit is provided with a variable attenuation section 101 receiving an input signal, a variable gain amplifier section 102 receiving an output of the variable attenuation section 101, and a linearizer 104 generating a control voltage Cont1 to control respectively a negative gain and a gain. Furthermore, the absolute value of the negative gain with respect to the control voltage Cont1 of the variable attenuation section 101 is increased as the input signal increases and the gain of the variable gain amplifier section 102 is decreased as the absolute value of the negative gain of the variable attenuation section 101 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to GSM, EGS
The present invention relates to an automatic gain control amplifier used in a digital cellular phone such as M, DCS1800, PCS1900 and the like and a receiving circuit using the same, and more particularly, to an automatic gain control for obtaining a sufficient dynamic range while suppressing noise of the receiving circuit. The present invention relates to an amplifier and a receiving circuit using the same.

[0002]

2. Description of the Related Art Conventionally, GSM (Global System for M
Obile communication) type mobile phones are known.
In this method, GMSK (Gaussian Filtered Min
imum Shift Keying) modulation method. FIG.
Is a block diagram showing an example of a receiving circuit of a mobile phone adopting the GSM system. As shown in FIG. 22, the receiving circuit 10 includes a front end unit 12 that receives a signal received by an antenna (not shown), a first mixer 14, an intermediate frequency amplifying unit 16, a second A mixer 18, an automatic gain control amplifier 20 ′, and a quadrature demodulator 22 are provided.

In such a receiving circuit 10, a signal given to the front end section 12 is amplified with a predetermined gain, and unnecessary spurious components other than the receiving band are removed. Next, the signal from which the spurious components have been removed is frequency-converted by the first mixer 14 to obtain a signal of a first intermediate frequency. The output signal of the first mixer 14 is amplified by the intermediate frequency amplifying unit 16 and further subjected to frequency conversion by the second mixer 18 to obtain a signal of the second intermediate frequency.

Then, according to the control voltage Cont1,
The level of the output signal of the second mixer 18 is adjusted by the automatic gain control amplifier 20 'whose gain is determined,
The level-adjusted signal is output to quadrature demodulation section 22. The quadrature demodulation unit 22 distributes an output signal of an oscillator (not shown), shifts the phase of one of the signals by 90 ° to generate two signals that are orthogonal to each other, and uses these to generate an automatic gain. The signal provided by the control unit 20 'is demodulated to obtain a complex baseband signal (I signal and Q signal). Such a method in which frequency conversion is performed twice in the receiving circuit is referred to as a double conversion method.

In the receiving circuit 10, the automatic gain control amplifier 20 'controls the amplitudes of the I signal and Q signal output from the quadrature demodulation unit 22 to be constant regardless of the size of the signal received by the antenna. It is controlled by the voltage Cont1.

FIG. 23 is a block diagram showing another example of a receiving circuit of a portable telephone adopting the GSM system. The receiving circuit 30 includes a front end unit 12, a first mixer 24, an automatic gain control amplifier 20 ', and a quadrature demodulator 22. In the receiving circuit 30, a signal provided from an antenna (not shown) to the front end unit 12 is amplified with a predetermined gain, and unnecessary spurious components other than the reception band are removed. Next, the signal from which the spurious components have been removed is frequency-converted by the first mixer 24 to obtain a signal of a first intermediate frequency.
Thereafter, the control voltage C is controlled by the automatic gain control amplifier 20 '.
The signal level is adjusted with the gain according to ont1, and the level-adjusted signal is output to the quadrature demodulation unit 22.
The quadrature demodulator 22 distributes the output signal of the oscillator (not shown), shifts the phase of one of the signals by 90 ° to generate two mutually orthogonal signals, and
The signal provided by the automatic gain control unit 20 'is demodulated to obtain a complex baseband signal (I signal and Q signal). Such a circuit in which one frequency conversion is performed in the receiving circuit is referred to as a single conversion method.

FIG. 24 is a block diagram showing a circuit configuration of a conventional automatic gain control amplifier 20 '(hereinafter, referred to as an "AGC circuit") used in the receiving circuits shown in FIGS. This automatic gain control amplifier 2
0 ′ has a variable gain amplifying section 102 composed of a plurality of differential amplifiers 102-1 to 102-n, an output amplifier 103 for amplifying a received signal with a fixed gain, and a linearizer 104. In the linearizer 104,
A control voltage Cont1 is supplied, and a differential amplifier 102 constituting a variable gain amplifying unit 102 is provided in accordance with the control signal.
Gain control voltages g1 to gn indicating respective gains are applied to each of -1 to 102-n.

Each of differential amplifiers 102-1 to 102-2 is formed of, for example, a bipolar transistor and is controlled by gain control voltages g1 to gn, which are analog signals.

The signals received by the AGC circuit 20 'constructed as described above are supplied to the differential amplifiers 102-1 to 102-2 whose gains are adjusted in accordance with the gain control voltages g1 to gn provided by the linearizer 104.
By -n, the signal is amplified so as to have a predetermined output amplitude.

The output signal from the variable gain amplifier 102 is
Further, the signal is amplified by the output amplifier 103 with a fixed gain. The linearizer 104 also performs temperature compensation.

FIG. 25 is a graph showing an example of a gain characteristic of a conventional AGC circuit with respect to a control signal.
In this example, the gain (Gain) increases as the control voltage Cont1 increases. The graph showing this characteristic (the straight line 2501 in the figure) may be downward instead of upward, but must be continuous and monotonically increasing or monotonically decreasing. That is, as the signal applied to the AGC circuit increases, its gain needs to decrease monotonically.

According to the GSM standard, the standard sensitivity is -102.
The circuit must operate linearly with a dynamic range of at least 62 dB from dBm to a maximum input level of -40 dBm (from NER standards). That is,
Any level input that falls within the range
When applied to a C circuit, it is necessary to obtain I and Q signals having almost constant output amplitude without distortion. Therefore, when the input level at the antenna is -102 dBm, the gain setting value (control voltage value) of the AGC circuit is -40 dB.
The difference from the gain setting value (control voltage value) in the case of m needs to be at least 62 dB or more. Therefore, in general, the dynamic range of the AGC circuit provided in the GSM receiving apparatus is set to be very wide, about 80 dB.

FIG. 26 is a graph showing an example of characteristics of the noise figure NF and the maximum allowable input level with respect to the control voltage of the conventional AGC circuit. For example, consider the above characteristic in the case where a signal is directly supplied to the variable gain amplifying section 102 of the AGC circuit as shown in FIG. 24 and the variable gain amplifying section is made by a bipolar process. The maximum allowable input level of the variable gain amplifying section is mainly determined by the differential amplifier (the differential amplifier 10 in FIG.
2-1) is determined by the current and the emitter resistance. Therefore, in order to increase the dynamic range of the input, that is, to increase the maximum allowable input level, it is necessary to increase the current and / or to increase the emitter resistance. However, since a mobile phone is driven by a battery, it is required to reduce current consumption and extend operation time. Therefore, AG
It is impossible to increase the current of the C circuit. Therefore, in order to increase the dynamic range of the input,
The emitter resistance is increased.

On the other hand, when the emitter resistance is increased,
The noise figure NF characteristic of the AGC circuit is deteriorated, and the noise of the entire receiving circuit is increased. As a result, the receiving sensitivity may be deteriorated. Therefore, the current and the emitter resistance are determined by optimizing these characteristics.

[0015]

As shown in FIG. 24,
In the conventional AGC circuit, since a signal is directly input to the first-stage differential amplifier of the variable gain amplifying unit,
The emitter resistance of the first-stage differential amplifier is increased so as to realize a dynamic range extending to B. That is,
When the antenna input is the standard sensitivity of -102 dBm (corresponding to the control voltage V1 in FIG. 26), the maximum allowable input level (dynamic range) of the AGC circuit is determined according to the noise characteristic NF. The maximum allowable input level thus determined does not improve as the gain control voltage decreases (ie, as the gain decreases), but rather worsens as the current decreases. In order to prevent this, it is necessary to increase the current.

[0016] This makes it very difficult to reduce the current consumption of the mobile phone to enable long-time communication or to achieve high-sensitivity reception (low noise).

Further, when reducing the size and weight of the portable telephone, it is necessary to integrate all the receiving circuits including the front end unit 12 into ICs. At this time, depending on the IC manufacturing process, the gain of the AGC circuit may not be sufficiently secured. Therefore, the AG arranged at the subsequent stage
It is difficult to eliminate the influence of the noise of the C circuit.

An object of the present invention is to provide an automatic gain control circuit for a portable telephone which has reduced current consumption and improved reception sensitivity, and a receiving circuit using the same.

It is another object of the present invention to provide an automatic gain control circuit and a receiving circuit which can be integrated into a single IC without impairing the performance thereof.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic gain control for amplifying an input signal with a gain determined according to a control signal so that the amplitude of the input signal is substantially constant regardless of the amplitude of the input signal. An amplifier, a variable attenuator for receiving an input signal, a variable gain amplifier connected to the variable attenuator and receiving an output of the variable attenuator, and the variable attenuator and the variable gain based on the control signal. A first gain control signal and a second gain control signal for controlling the negative gain and the gain of the amplifier, respectively, and providing these to the variable attenuator and the variable gain amplifier, respectively; Control signal generating means, wherein the input signal received by the variable attenuator is attenuated according to the first gain control signal and the second gain control signal. Is output from the attenuator,
The variable gain amplifying unit is configured to amplify the received signal, and the absolute value of the negative gain of the variable attenuating unit with respect to the control signal increases as the input signal increases due to the control signal. Is configured to
The automatic gain control amplifier is characterized in that the gain of the variable gain amplifier with respect to the control signal decreases as the absolute value of the negative gain increases.

According to the present invention, a variable attenuator is arranged in front of the conventional variable gain amplifying section, and the absolute value of the negative gain of the variable attenuating section with respect to the control signal is determined by the control signal. The gain of the variable gain amplifying section with respect to the control signal is configured to decrease as the absolute value of the negative gain increases as the absolute value of the negative gain increases. Therefore, as the gain of the automatic gain amplifier decreases, the maximum allowable input level that can be input to the automatic gain control amplifier can be increased. That is, when the gain of the automatic gain control amplifier is to be reduced, the maximum allowable input level can be further increased by increasing the attenuation (absolute value of the negative gain) of the variable attenuator.

In a preferred embodiment of the present invention, the variable attenuator is configured such that the characteristic of the negative gain with respect to the control signal changes substantially monotonously and substantially continuously, and the variable gain amplifying unit controls the control signal. The gain characteristic of the signal is configured to change substantially monotonically and substantially continuously.

According to this embodiment, the gain characteristics of the entire variable gain amplifying section with respect to the control signal can be changed substantially monotonously and continuously. For this reason, it is possible to amplify the input signal while maintaining the linearity.

In a further preferred aspect of the present invention, the characteristic of the negative gain of the variable attenuator with respect to the control signal is substantially monotonic and substantially continuous except at least at a discontinuous point, and The gain characteristic of the variable gain amplifying unit with respect to the control signal is configured to be substantially monotonic and substantially continuous except at least at the discontinuous point.

In a further preferred aspect of the present invention, the variable attenuating section and the variable gain amplifying section each have a characteristic of a negative gain of the variable attenuating section with respect to the control signal;
The first gain control signal and the second gain control signal are output by the gain control signal generating means so that the sum of the control signal and the gain characteristic of the variable gain amplifying section is substantially monotonous and continuous. 2 gain control signals are generated,
A negative gain characteristic of the variable attenuator and a gain characteristic of the variable gain amplifier are determined.

According to this embodiment, the gain characteristics of the entire variable gain amplifying section with respect to the control signal can be changed substantially monotonously and continuously. For this reason, it is possible to amplify the input signal while maintaining the linearity.

In a further preferred aspect of the present invention, the temperature dependence of the negative gain characteristic of the variable attenuator with respect to the control signal is dependent on the gain characteristic of the variable gain amplifier with respect to the control signal. The temperature dependence is reversed, and the sum of the negative gain characteristic of the variable attenuator and the gain characteristic of the variable gain amplifier has no temperature dependence.

In a further preferred aspect of the present invention, as the gain of the automatic control gain amplifier decreases, the maximum allowable input level at which the automatic control gain amplifier can maintain linearity increases. ,
The gain control signal generating means is configured to generate a first gain control signal and a second gain control signal to be provided to the variable attenuator and the variable gain amplifier.

In another embodiment of the present invention, an automatic gain control amplifier amplifies an input signal with a gain determined according to a control signal such that its amplitude is substantially constant regardless of the amplitude of the input signal. There is one input side,
Having at least a plurality of outputs and receiving the signal;
Switching means for providing at least a selected one of the plurality of outputs and at least a plurality of attenuators each connected to one of the plurality of outputs of the switching means and receiving one of its outputs. And a variable gain amplifying unit connected to each of the plurality of attenuators, and receiving a control signal, and generating a plurality of gain control signals for controlling gains of the plurality of variable gain amplifying units based on the control signal. do it,
And a gain control signal generating means for supplying these to the plurality of variable gain amplifying sections, and one of the variable gain amplifying sections connected to the output side selected by the switching means via one of the attenuators. The output side is selected by the switching means so that the output signal from the control signal changes substantially monotonically and substantially continuously except at least at the discontinuous point in accordance with the change of the control signal, and the plurality of variable gains are selected. The gain of the selected one of the amplifying units with respect to the control signal is determined.

According to this embodiment, the gain control is performed such that the output signal from the selected one of the plurality of variable gain amplifying sections changes substantially monotonously and substantially continuously in accordance with the change of the control signal. By the signal generation means, the gain control signal is
The variable gain amplifier is supplied to the plurality of variable gain amplifiers, and one of the plurality of variable gain amplifiers is selected by the switching unit. Therefore, an appropriate variable gain amplifier is selected by the switching unit according to the level of the input signal. It is possible to do. Thereby, when the gain of the whole automatic gain control amplifier is small,
The maximum allowable input level can be set appropriately.

In a preferred embodiment of the present invention, the power supply of the variable gain amplifying units other than one of the plurality of variable gain amplifying units selected by the switching unit is turned off. As a result, power consumption can be reduced without deteriorating the performance of the automatic gain control amplifier.

Further, in the above embodiment, each of the plurality of attenuators may be a fixed attenuator having a different amount of attenuation from each other, or according to another gain control signal generated by the gain control signal generating means. A variable attenuator that attenuates the received signal with the amount of attenuation may be used.

In a preferred embodiment of the present invention, as the gain of the automatic control gain amplifier decreases, the maximum allowable input level at which the automatic control gain amplifier can maintain linearity increases. To
The gain control signal generating means is configured to generate a gain control signal to be provided to each of the plurality of variable gain control means and / or another gain control signal to be provided to the plurality of attenuators.

Further, an object of the present invention is to provide a variable gain amplifier for receiving an output from a first mixer and amplifying the received signal with a gain according to a first control signal in a double conversion type receiving circuit. The gain control signal generating means, the first control signal, so that the gain of the variable gain amplifier and the automatic gain control amplifier decreases as the electric field strength of the signal from the antenna increases, and This is also achieved by a receiving circuit configured to generate a second control signal that controls the gain of the automatic gain control amplifier.

[0035]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
1 is a block diagram of an automatic gain control amplifier (hereinafter, referred to as an “AGC circuit”) according to a first embodiment of the present invention. As shown in FIG. 1, an AGC circuit 20 according to this embodiment includes a variable attenuator 101, a variable gain amplifier 102 including a plurality of differential amplifiers 102-1 to 102-n, an output amplifier 103, Linearizer 1
04. Among these, the variable gain amplifier 1
02, the output amplifier 103 and the linearizer 104
Since they are the same as those shown in FIG. 24, the same numbers are given. The configuration of the receiving circuit 10 using the AGC circuit according to this embodiment is the same as that shown in FIG. As will be described in detail later, the variable attenuator 101 has the characteristic of the amount of attenuation (absolute value of negative gain) with respect to the control voltage opposite to that of the variable gain amplifier 102.
Further, the variable attenuator 101 and the variable gain amplifier 102
Are manufactured by a bipolar process, and the gain is controlled by an analog signal.

In the AGC circuit 20 configured as described above, the signal (AGCin) given from the second mixer 18 (see FIG. 22) is once received by the variable attenuator 101. The variable attenuator 101 adjusts the amplitude of the received signal and supplies the signal attenuated with a predetermined negative gain to the first-stage differential amplifier 102-1 of the variable gain amplifier 102.
Differential amplifier 102-1 constituting variable gain amplifying section 102
To 102-n, the signal is amplified, and the signal amplified by the variable gain amplifying unit 102 is output to the output amplifier 1
03 and further amplified with a fixed gain.

In the AGC circuit 20 according to this embodiment, the linearizer 104 receives the control voltage Cont1, and according to this control signal, the variable attenuator 101
, A first gain control voltage gv indicating the gain, and a differential amplifier 10
Each of 2-1 to 102-n has a gain control voltage g1
Or give gn.

FIG. 2 is a graph showing a gain characteristic with respect to a control voltage of the AGC circuit 20 according to the first embodiment. In FIG. 2, the characteristic of the variable attenuator 101 corresponds to a straight line 201, while the characteristic of the variable gain amplifier 1
The characteristic of 02 corresponds to the straight line 202. As shown in FIG. 2, the variable attenuator 101 has such a characteristic that the amount of attenuation (absolute value of negative gain) monotonously decreases as the control voltage Cont1 increases. On the other hand, the variable gain amplifying section 102 has such a characteristic that its gain monotonically increases as the control voltage Cont1 increases. That is, the characteristic of the amount of attenuation (absolute value of the negative gain) of the variable attenuator 101 with respect to the control voltage Cont1 is opposite to the characteristic of the gain of the control voltage Cont1 of the variable gain amplifier 102. Therefore, the gain characteristic of the entire AGC circuit 20 with respect to the control voltage Cont1 is represented by a straight line 203 in FIG.
It becomes as shown in.

As described above, according to the GSM standard,
Standard sensitivity -102dBm to maximum input level -40dB
The circuit must operate linearly with a dynamic range of at least 62 dB, up to m (from NER standards). In the AGC circuit, no matter what level of input is given, it is necessary to obtain I signals and Q signals having almost constant output amplitudes without distortion. Therefore, in the present embodiment, the dynamic range of the AGC circuit is
It is set to be at least 62 dB or more.

Next, the noise figure NF and the maximum allowable input level with respect to the control voltage of the AGC circuit according to this embodiment will be described. As described above, the maximum input level is mainly determined by the current and the emitter resistance of the first-stage differential amplifier of the variable gain amplifier.
Therefore, increasing the dynamic range of the input,
That is, in order to increase the maximum allowable input level, it is necessary to increase the current and / or to increase the emitter resistance. As described above, it is difficult to increase the current, or increasing the emitter resistance deteriorates the noise figure NF characteristic of the AGC circuit. Alternatively, a method may be conceived in which the signal is attenuated at a stage further upstream of the differential amplifier at the first stage of the variable gain amplifying unit to expand the linear input range. However, similar to increasing the emitter resistance, the AGC
The noise figure NF characteristic of the circuit deteriorates, and as a result, the noise of the entire receiving circuit increases.

On the other hand, in the present embodiment,
As shown in FIG. 1, the characteristic of the attenuation (absolute value of the negative gain) with respect to the control voltage Cont1 is opposite to the characteristic of the gain with respect to the control voltage Cont1 of the variable gain amplifying unit 102 at a stage preceding the variable gain amplifying unit 102. The variable attenuator 101 is provided to give the AGC circuit 20 a gain characteristic as shown in FIG.

FIG. 3 shows an AGC according to the first embodiment.
4 is a graph showing a maximum allowable input level and a noise figure NF with respect to a control voltage of the circuit. In FIG. 3, the maximum allowable input level (MIV) for the control voltage of the AGC circuit is shown.
Corresponds to the straight line 301. In the straight line 301, the value corresponding to the control voltage V2 of the AGC circuit when the input level is -40 dBm, which is the maximum, is the largest. That is, the maximum allowable input level can be set higher. This is because the signal is most attenuated by the variable attenuator 101 when the input level is -40 dBm.

On the other hand, in FIG. 3, the noise figure NF with respect to the control voltage of the AGC circuit corresponds to the straight line 302. In the straight line 302, the value corresponding to the control voltage V1 of the AGC circuit when the input level is the standard sensitivity of -102 dBm is smaller. That is, by reducing the attenuation (negative gain) of the variable attenuator 101, the noise figure of the first stage is improved, so that the noise figure NF necessary for the AGC circuit can be secured.

Therefore, according to the present embodiment, a portable telephone equipped with a receiving circuit including this AGC circuit is
Even when operated at low voltage and the current consumption is kept low, when the input signal is small, the noise characteristics are maintained well, and when the input signal is large, the maximum allowable input is sufficient. Levels can be secured.

In this embodiment, the characteristic of the temperature change with respect to the control voltage Cont1 of the variable attenuator 101 is as follows:
It is preferable that the characteristic of the temperature change with respect to the control voltage Cont1 of the variable gain control unit 102 be reversed so that they are canceled when they are combined.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram of an AGC circuit according to a second embodiment of the present invention. As shown in FIG. 4, the AGC circuit 40 according to this embodiment includes:
A switching unit 705 that has one input and two outputs, receives a signal (AGCin) given from the first mixer 18 (see FIG. 22) on the input side, and outputs this to one of the output sides.
A variable attenuator 110 connected to one output of the switching unit 705; a variable gain amplifying unit 102 including differential amplifiers 102-1 to 102-n; an output amplifier 103; a linearizer 104; 106 and the switching unit 70
5, a second variable gain amplifying section 107 including differential amplifiers 107-1 to 107-n, an output amplifier 108, a linearizer 109, and a variable gain amplifying section. There is provided a second switching unit 706 having two inputs for receiving the output of the variable gain amplifying unit 107 or the output of one of the received inputs, respectively. 4, the same components as those of the AGC circuit according to the first embodiment shown in FIG. 1 are denoted by the same reference numerals. However, in this embodiment, the differential amplifiers 102-1 to 102-n and 107-1 to 107-n are constituted by digital circuits composed of CMOS transistors.

The configurations of the output amplifier 108 and the linearizer 109 are almost the same as those of the output amplifier 102 and the linearizer 104. However, the gain control voltages ggv and gg1 to ggn output from the linearizer 109 to the variable attenuator 111 and the differential amplifiers 107-1 to 107-n based on the control voltage Cont1 are output from the linearizer 104 to the variable attenuator 110. And the gain control voltages gv and g1 to gn output to the differential amplifiers 102-1 to 102-n. As a result, the gain characteristic of the variable gain amplifier 107 with respect to the control voltage Cont1 is as follows:
The configuration differs from that of the variable gain amplifying unit 102.

The switching section 705 includes a high frequency switch 801 as shown in FIG. High frequency switch 80
Numeral 1 has one input terminal and two output terminals, and connects one of the input side and the two output sides in accordance with a switch switching signal SW described later. The second switching unit 706 has the same configuration as the first switching unit 705. Also, the switching unit 706 is
5, and one of the two input sides is connected to the output side in accordance with the switch signal SW.

The configuration of a receiving circuit using the AGC circuit according to this embodiment is the same as that shown in FIG.

The AGC circuit 4 constructed as described above
At 0, the signal (AGCin) provided from the second mixer 18 (see FIG. 22) is provided to the switching unit 705. This signal is sent to the first variable attenuator 110 or the second variable attenuator 1 via the high-frequency switch 801 of the switching unit 705.
11 is given.

A signal supplied to one of the first variable attenuator 110 and the second variable attenuator 111 is a control signal gv or gg supplied from the linearizer 104 or 109.
The signal attenuated by the amount of attenuation (negative gain) based on v is provided to the variable gain amplifying unit 102 or 107.

The differential amplifiers 102-1 through 1202-n or 1 constituting the variable gain amplifying unit 102 or 107
07-1 to 107-n, the linearizer 1
The received signal is amplified with a predetermined gain based on the gain control voltage g1 to gn or gg1 to ggn output by 04 or 109. The signal output from the variable gain amplifier 102 is received by the output amplifier 103,
Further, it is amplified with a fixed gain. Alternatively, the signal output from the variable gain amplifier 107 is
8 and further amplified with a fixed gain.

The signal amplified by one of the variable gain amplifying units 102 and 107 is supplied to the switching unit 706. Switching section 706 outputs the output signal from the variable gain amplifying section to which the signal has been given by switching section 705 to the outside of AGC circuit 50 in accordance with switch switching signal SW.

Next, the gain characteristics of the variable gain amplifiers 102 and 107 will be described. FIG. 5 is a graph illustrating gain characteristics of the AGC circuit according to the second embodiment with respect to the control voltage Cont1. FIG. 5A shows a gain characteristic of the variable gain amplifying section 102, and FIG. 5B shows a gain characteristic of the variable gain amplifying section 107. On the other hand, FIG.
(C) and (d) respectively show the variable gain amplifier 102,
Noise figure NF for control voltage Cont1 at 107
6 is a graph showing a maximum allowable input. FIG. 5 (a),
As shown in FIG. 5B, in this embodiment, the gain characteristics (the straight line 501 in FIG. 5A and the straight line 502 in FIG. 5B) of the variable gain amplifiers 102 and 107 with respect to the control voltage are as follows. , Are set almost the same. That is,
These gains are monotonically increased at a certain slope as the control voltage Cont1 increases.

However, the characteristic of the amount of attenuation (absolute value of the negative gain) with respect to the control voltage Cont1 of the variable attenuator 110 installed before the variable gain amplifier 102 is changed by the variable attenuator 110 installed before the variable gain amplifier 107. Of the attenuator 111,
This is different from the attenuation for the control voltage Cont1. That is,
Both the variable attenuator 110 and the variable attenuator 111 have such characteristics that the attenuation (absolute value of negative gain) decreases substantially monotonically as the control voltage Cont1 increases. , The amount of attenuation of the variable attenuator 110
Is always bigger.

Therefore, the maximum allowable input level (MIV) of the variable gain amplifying section 102 via the variable attenuator 110 (FIG. 5)
The straight line 503 in FIG. 5C is larger than the maximum allowable input level of the variable gain amplifying unit 107 through the variable attenuator 111 (the straight line 504 in FIG. 5D). On the other hand, the noise characteristic NF of the variable gain amplifier 107 (the straight line 505 in FIG. 5D) is better than the noise characteristic NF of the variable gain amplifier 102 (the straight line 506 in FIG. 5C). That is,
When the input level is high (for example, at -40 dBm), the AGC circuit realizes the maximum input level shown in FIG. 5C, and when the input level is low (for example, at -120 dBm). Preferably realizes the noise characteristic NF shown in FIG.

Therefore, in this embodiment, the switching signal SW is provided to the switching unit 705 so as to switch the high frequency switch 801 when the control voltage is at the predetermined value V3. Therefore, when the value of the control voltage Cont1 is V2 or V3, the signal (AGCin) from the second mixer 18 is changed by the high frequency switch 801 to the variable attenuator 11
0, on the other hand, when the value of the control voltage Cont1 is between V3 and V1, the signal (AGCin) is sent to the variable gain amplifier 107 through the variable attenuator 111 by the high frequency switch. Given.
As a result, the gain characteristic of the AGC circuit with respect to the control voltage is
As shown in FIG. 9E, the value increases monotonically (straight line 507).
reference).

Next, a description will be given of the noise base NF and the maximum allowable input level with respect to the control voltage Cont1 of the AGC circuit 40 according to the second embodiment. FIG. 6 is a graph showing the maximum allowable input level and the noise figure NF of the AGC circuit according to this embodiment with respect to the control voltage Cont1. As described above, when the value of the control voltage Cont1 is V2 or V3, the high-frequency switch 8 of the switching unit 705
01, the signal (AGCin) from the second mixer 18 is
The control voltage is supplied to the variable gain amplifier 102 via the variable attenuator 110, while the value of the control voltage Cont1 is V3 to V
At 1, the signal (AGCin) is supplied to the variable gain amplifier 107 via the variable attenuator 111 by the high frequency switch 801 of the switching unit 705. Therefore, the maximum allowable input level for the control voltage Cont1 of the entire AGC circuit 50 corresponds to the polygonal line 601 and the noise figure NF for the control voltage Cont1 corresponds to the polygonal line 602. That is, when the control voltage Cont1 is in the range of V2 or V3, the maximum allowable input level matches the maximum allowable input level (straight line 503) of the variable gain amplifier 102 shown in FIG. When the voltage Cont1 is in the range from V3 to V1, the maximum allowable input level is as shown in FIG.
This corresponds to the maximum allowable input level (straight line 504) of the variable gain amplifier 107 shown in (d).

When the control voltage Cont1 is V2 or V3
, The noise figure NF matches the corresponding noise figure NF (straight line 506) of the variable gain amplifier 102 shown in FIG. 5C, while the control voltage Cont1 is
When in the range from 3 to V1, the noise figure NF is
The noise figure NF of the variable gain amplifier 107 shown in FIG.
(Line 505).

As can be understood from FIG. 6, in this embodiment, similarly to the second embodiment, when the input level is -40 dBm, which is the maximum input level (when the control voltage is V2), The maximum allowable input level can be made sufficiently large. On the other hand, when the input level is the standard sensitivity of -120 dBm (at the control voltage V1),
The required noise figure NF can be secured.

According to the present embodiment, when the control voltage Cont1 reaches the predetermined value V3, the first variable attenuator 110 and the first variable gain amplifying section 102 operate, and on the other hand,
When the control voltage Cont1 is larger than the predetermined value, the second
Variable attenuator 111 and second variable gain amplifying unit 10
7 is activated, and the gain of the AGC circuit with respect to the control voltage Cont1 becomes substantially monotonous so that the variable gain amplifying sections 102, 10
7 are determined. Also, the control voltage Co
Regardless of the value of nt1, the amount of attenuation (negative gain) of the first variable attenuator 110 is determined to be greater than the amount of attenuation (absolute value of negative gain) of the second variable attenuator 111. . For this reason, even when a mobile phone equipped with a receiving circuit including an AGC circuit is operated at a low voltage and its current consumption is kept low, when a small signal is input, the noise characteristic becomes low. And when a large signal is input, it is possible to ensure a sufficient maximum allowable input level.

Further, in this embodiment, if the power of the fixed attenuator and the variable gain amplifying unit not selected by the switching unit 705 is turned off, the current consumption of the circuit can be further reduced.

Next, a third embodiment of the present invention will be described. FIG. 7 is a block diagram of the AGC circuit according to this embodiment. 7, the configurations of switching units 705 and 706, variable gain amplifying units 102 and 107, output amplifiers 103 and 108, signal combining unit 106, and linearizers 104 and 109 are the same as those according to the second embodiment shown in FIG. Is substantially the same as In the AGC circuit 50 according to this embodiment, the variable amplifier 1
02, 107, the first fixed attenuator 7
10 and a second fixed attenuator 711 are arranged.
As will be described later, the attenuation of these fixed attenuators is different from each other. The configuration of the receiving circuit using the AGC circuit according to this embodiment is the same as that shown in FIG.

As shown in FIG. 7, the AGC circuit 50 according to this embodiment includes a first mixer 18 (see FIG. 22).
The first fixed attenuator 710 and the variable gain amplifying unit 10 connected to the first fixed attenuator 710
2 or the second fixed attenuator 7111 and one of the variable gain amplifying units 107 connected to the second fixed attenuator 7111 and the switching unit 705 for outputting the received signal. A second switching unit 706 that receives each output signal and outputs one of the output signals to the outside of the AGC circuit 50.

The structure of the switching units 705 and 706 is as follows.
This is the same as that of the second embodiment (see FIG. 8).

Now, the AGC circuit 5 configured as described above
At 0, the signal (AGCin) provided from the second mixer 18 (see FIG. 22) is provided to the switching unit 705. This signal is supplied to the first fixed attenuator 710 or the second fixed attenuator 7 via the high-frequency switch 801 of the switching unit 705.
11 is given.

The signal provided to one of the first fixed attenuator 710 and the second fixed attenuator 711 is attenuated by a predetermined amount of attenuation (negative gain), and the attenuated signal is converted to a variable gain amplifier. 102 or 107.

The differential amplifiers 102-1 through 1202-n or 1 constituting the variable gain amplifying section 102 or 107
07-1 to 107-n, the linearizer 1
The received signal is amplified with a predetermined gain based on the gain control voltage g1 to gn or gg1 to ggn output by 04 or 109. The signal output from the variable gain amplifier 102 is received by the output amplifier 103,
Further, it is amplified with a fixed gain. Alternatively, the signal output from the variable gain amplifier 107 is
8 and further amplified with a fixed gain.

The signal amplified by either variable gain amplifying section 102 or 107 is applied to switching section 706. Switching section 706 outputs the variable gain amplifying section to which the signal has been given by switching section 705 to the outside of AGC circuit 50 according to switch switching signal SW.

Next, the gain characteristics of the variable gain amplifiers 102 and 107 will be described. FIG. 9 is a graph showing gain characteristics of the AGC circuit according to the third embodiment with respect to the control voltage Cont1. FIG. 9A shows the variable gain amplifying unit 1.
9 shows the gain characteristic of the variable gain amplifying unit 107. FIG. On the other hand, FIG.
(C) and (d) respectively show the variable gain amplifier 102,
FIG. 107 is a graph showing a noise figure NF and a maximum allowable input with respect to a control voltage Cont1 of FIG. FIGS. 9A and 9B
As shown in FIG. 9, in this embodiment, the gain characteristics of the variable gain amplifiers 102 and 107 with respect to the control voltage (the straight line 901 in FIG. 9A and the straight line 90 in FIG. 9B).
2) is set almost the same. That is, these gains increase as the control voltage Cont1 increases.
At a certain slope, it increases monotonically.

However, the attenuation (absolute value of the negative gain) of the fixed attenuator 710 provided before the variable gain amplifier 102 is smaller than the attenuation of the fixed attenuator 711 provided before the variable gain amplifier 107. Is also set large. Therefore, the maximum allowable input level (MIV) of the variable gain amplifying section 102 (the straight line 903 in FIG. 9C) and the maximum allowable input level of the variable gain amplifying section 107 (the straight line 9 in FIG. 9D).
04) It is larger. On the other hand, the noise characteristic NF of the variable gain amplifier 107 (the straight line 90 in FIG. 9D)
5) is a noise characteristic NF of the variable gain amplifying section 102 (FIG. 9).
(C) is better than the straight line 906). That is, when the input level is high (for example, at -40 dBm), the AGC circuit realizes the maximum input level shown in FIG. 9C, and when the input level is low (for example,
In the case of -120 dBm, for example), it is preferable to realize the noise characteristic NF shown in FIG.

Therefore, in this embodiment, the switching signal SW is provided to the switching section 705 so as to switch the high frequency switch 801 when the control voltage is at the predetermined value V3. Therefore, when the value of the control voltage Cont1 is V2 or V3, the signal (AGCin) from the second mixer 18 is fixed by the high frequency switch 801 to the fixed attenuator 71.
0, on the other hand, when the value of the control voltage Cont1 is between V3 and V1, the signal (AGCin) is sent to the variable gain amplifier 107 via the fixed attenuator 711 by the high frequency switch. Given.
As a result, the gain characteristic of the AGC circuit with respect to the control voltage is
As shown in FIG. 9E, the value increases monotonically (straight line 907).
reference).

Next, a description will be given of the noise base NF and the maximum allowable input level with respect to the control voltage Cont1 of the AGC circuit 50 according to the third embodiment. FIG. 10 is a graph showing the maximum allowable input level and the noise figure NF with respect to the control voltage Cont1 of the AGC circuit according to this embodiment. As described above, the value of the control voltage Cont1 is V2
Or V3, the high frequency switch 801
The signal (AGCin) from the second mixer 18 is supplied to the fixed attenuator 7
When the value of the control voltage Cont1 is between V3 and V1, the signal (AGCin) is supplied to the variable gain amplifier 107 through the fixed attenuator 711 when the value of the control voltage Cont1 is between V3 and V1. Given.
Therefore, the maximum allowable input level for the control voltage Cont1 of the entire AGC circuit 50 corresponds to the polygonal line 1001, and the noise figure NF for the control voltage Cont1 is represented by the polygonal line 1002.
Corresponding to That is, when the control voltage Cont1 is in the range of V2 or V3, the maximum allowable input level matches the maximum allowable input level (straight line 903) of the variable gain amplifier 102 shown in FIG. Voltage Cont
When 1 is in the range of V3 to V1, the maximum allowable input level is the variable gain amplifier 107 shown in FIG.
(The straight line 904).

When the control voltage Cont1 is V2 or V3
, The noise figure NF matches the corresponding noise figure NF (straight line 906) of the variable gain amplifier 102 shown in FIG. 9C, while the control voltage Cont1 is
When in the range from 3 to V1, the noise figure NF is
The noise figure NF of the variable gain amplifier 107 shown in FIG.
(Straight line 905).

As can be understood from FIG. 10, in this embodiment, similarly to the second embodiment, when the input level is the maximum input level of -40 dBm (when the control voltage is V2), The maximum allowable input level can be made sufficiently large, while the input level is -120 dBm which is the standard sensitivity (when the control voltage is V1).
In addition, the required noise figure NF can be secured.

According to the present embodiment, when the control voltage Cont1 is up to the predetermined value V3, the first fixed attenuator 710 and the first variable gain amplifying section 102 operate.
When the control voltage Cont1 is larger than the predetermined value, the second
Fixed attenuator 711 and second variable gain amplifier 10
7 is activated, and the gain of the AGC circuit with respect to the control voltage Cont1 becomes substantially monotonous so that the variable gain amplifying sections 102, 10
7 are determined. Further, the amount of attenuation (negative gain) of the first fixed attenuator 710 is determined to be larger than the amount of attenuation (absolute value of negative gain) of the second fixed attenuator 711. For this reason, even when a mobile phone equipped with a receiving circuit including an AGC circuit is operated at a low voltage and its current consumption is kept low, when a small signal is input, the noise characteristic becomes low. And when a large signal is input, it is possible to ensure a sufficient maximum allowable input level.

Further, in this embodiment, if the power of the fixed attenuator and the variable gain amplifying unit not selected by the switching unit 705 is turned off, the current consumption of the circuit can be further reduced.

Next, a fourth embodiment of the present invention will be described. FIG. 11 illustrates an AG according to the fourth embodiment.
FIG. 12 is a block diagram showing the configuration of the C circuit.
4 is a block diagram showing a configuration of a receiving circuit using the AGC circuit according to the embodiment. As shown in FIG. 11, the configuration of an AGC circuit 60 according to this embodiment is the same as that of the AGC circuit according to the first embodiment shown in FIG. 1, except for the following matters. In this embodiment, from the linearizer to the variable attenuator 101,
Instead of providing the gain control voltage gv, another control voltage Co
nt2 is given.

As shown in FIG. 12, the receiving circuit using the AGC circuit 60 according to the fourth embodiment has
This is almost the same as that of the first embodiment except that two control voltages Cont1 and Cont2 are applied to the C circuit 60.

In the AGC circuit 60 thus configured, the signal (AGCin) given from the second mixer 18 (see FIG. 22) is given to the variable attenuator 101. The variable attenuator 101 adjusts the amplitude of the received signal, and provides the signal attenuated by a predetermined amount of attenuation to the first-stage differential amplifier 102-1 of the variable gain amplifier 102. In the variable gain amplifying section 102, as in the first embodiment, the signal is amplified, and the signal amplified by the variable gain amplifying section 102 is further amplified by the output amplifier 103 with a fixed gain. You.

Next, the gain characteristics of the variable attenuator 101 and the variable gain amplifier 102 according to this embodiment will be described.

In this embodiment, the variable attenuation unit 10
1 indicates that when the input signal is the largest (for example, at the maximum input level of −40 dBm), the attenuation (the absolute value of the negative gain) is the largest, while when the input signal is the smallest (for example, -10 which is the standard sensitivity
2dBm), the amount of attenuation (absolute value of negative gain)
Is the second control voltage Cont2 so that
Controls the amount of attenuation. That is, control is performed so that the amount of attenuation (absolute value of negative gain) increases as the amplitude of the input signal increases.

Therefore, the AG according to this embodiment
The gain characteristic of the C circuit is almost the same as that of the first embodiment. Here, in FIG. 3, the control voltage Co
Although the magnitude of nt1 is set on the horizontal axis, in the present embodiment, the input signal level may be changed such that the magnitude decreases as the horizontal axis advances to the right.
That is, as the level of the input signal decreases, the amount of attenuation (absolute value of the negative gain) of the variable attenuator 101 decreases substantially monotonously.
In No. 02, the gain increases almost monotonously as the level of the input signal decreases.

Therefore, also in this embodiment,
As in the first embodiment, the input level becomes the maximum-
When the input level is 40 dBm, the maximum input level of the AGC circuit can be larger. On the other hand, when the input level is -102 dBm, which is the minimum, a sufficient noise figure NF can be secured. Here, in FIG.
Although the magnitude of the control voltage Cont1 is set on the horizontal axis, in the present embodiment, the horizontal axis is shifted to the right,
What is necessary is just to change to the input signal level whose magnitude becomes small.

As described above, according to the present embodiment, a portable telephone equipped with a receiving circuit including this AGC circuit is
Even when operated at a low voltage and the current consumption is suppressed to a small value, when the input signal is large, the noise characteristics are maintained well, and when the input signal is large, the maximum allowable input is sufficient. Levels can be secured.

It will be understood that the AGC circuit according to the fourth embodiment can be applied to a receiving circuit 110 employing a single conversion system as shown in FIG.

Next, according to a fifth embodiment of the present invention,
Add a description. FIG. 14 is a block diagram showing the configuration of the receiving circuit according to this embodiment. FIG.
, The same components as those in FIG. 22 are denoted by the same reference numerals. As shown in FIG.
0, a front end unit 12 for receiving a signal received by an antenna (not shown), a first mixer 14,
It includes a first variable gain amplifier (AGC circuit) 216, a second mixer 18, a second AGC circuit 20 ′, and a quadrature demodulator 22.

The first AGC circuit 216, unlike the intermediate frequency amplifier 16 shown in FIG. 22, receives a control voltage Cont1 and amplifies a given signal with a gain according to the control voltage Cont1.

In the receiving circuit 200 configured as above, the signal given to the front end unit 12 is amplified with a predetermined gain, and unnecessary spurious components other than the receiving band are removed. Next, the signal from which the spurious signal has been removed is frequency-converted by the first mixer 24 to obtain the first signal.
Is obtained. The output signal of first mixer 14 is provided to first AGC circuit 216. First
AGC circuit 216 amplifies a given signal with a gain according to control voltage Cont1, and amplifies the amplified signal to a second level.
Is output to the mixer 18. Further, frequency conversion is performed by the second mixer 18, and a signal of the second intermediate frequency is obtained.

Thereafter, according to the control voltage Cont1,
By the second AGC circuit 20 'whose gain is determined,
The level of the output signal of the second mixer 18 is adjusted, and the level-adjusted signal is output to the quadrature demodulation unit 22. In the quadrature demodulation unit 22, the output signal of the oscillator (not shown) is divided into two signals, one of the signals is shifted by 90 ° to generate two mutually orthogonal signals, and these signals are used. , AGC circuit 20 'demodulates the signal provided thereto to obtain a complex baseband signal (I signal and Q signal).

Next, the first AG according to this embodiment
The gain for the control voltage of the C circuit 216, the second AGC circuit 20 'and the like will be described. FIG. 15 shows the first A
10 is a graph showing a gain characteristic of the GC circuit 216 with respect to a control voltage Cont1, and a gain characteristic of a second AGC circuit 20 ′ with respect to a control voltage Cont1. 15, the gain of the first AGC circuit 216 with respect to the control voltage Cont1 corresponds to the straight line 1501, and the gain of the second AGC circuit 20 'corresponds to the straight line 1502.

In the receiving circuit shown in FIG.
Since the amplitude of the signal given to the GC circuit 216 is small,
The need to consider the maximum allowable input level of the first AGC circuit 216 is relatively small. This is a general matter in a double conversion type receiving circuit.
Therefore, in the first AGC circuit 216, the first
The gain is determined in consideration of the noise characteristics NF of the second AGC circuit, the second mixer 18 and the second AGC circuit 20 ′, and the signal level to the second mixer 18.
That is, as shown in FIG. 16A, the control voltage Cont
When 1 is V1 (the input level is the standard sensitivity -102
The gain characteristic is determined so that the noise figure NF (in the case of dBm) (the straight line 1601) is sufficiently good.

The control voltage C of the second AGC circuit 20 '
The gain characteristic for ont1 is the same as that of the conventional one (FIG. 25), and its maximum allowable input level corresponds to the straight line 1602 in FIG. 16 (b).

Therefore, the maximum allowable input level and the noise figure NF of the receiving circuit according to this embodiment, more specifically, the first AGC circuit 216 to the second AGC circuit 20 ′ with respect to the control voltage Cont 1 are respectively FIG.
This corresponds to the straight lines 1603 and 1604 in (c).
That is, when the control voltage Cont1 is V2 (that is, when the input level is −40 dBm, which is the maximum level),
A sufficient maximum allowable input level can be ensured. On the other hand, when the control voltage Cont1 is V1 (that is, when the input level is -102 dBm which is the standard sensitivity), the gain setting of the first AGC circuit 216 is performed. By making the value smaller, the noise figure at the first stage is improved, so that a good noise figure NF can be obtained.

Therefore, according to the present embodiment, the portable telephone equipped with the receiving circuit is operated at a low voltage,
In addition, even when the current consumption is kept low, it is possible to maintain a good noise characteristic when the input signal is small and to secure a sufficient maximum allowable input level when the input signal is large. Becomes

Next, according to a sixth embodiment of the present invention,
Add a description. FIG. 17 is a block diagram showing the configuration of the receiving circuit according to this embodiment. FIG.
, The same components as those in FIGS. 24 and 14 are denoted by the same reference numerals. As shown in FIG. 17, the receiving circuit 300 includes a front end unit 12 for receiving a signal received by an antenna (not shown), a first mixer 14, a first AGC circuit 316, and a second , A second AGC circuit 20 ′, and a quadrature demodulator 22.

As shown in FIG. 17, the first AGC circuit 316 according to this embodiment includes a second control voltage Cont2
Is different from the first AGC circuit 216 according to the fifth embodiment shown in FIG. 14 in that the gain is controlled.

In the receiving circuit 300 configured as above, the signal given to the front end unit 12 is amplified with a predetermined gain, and unnecessary spurious components other than the receiving band are removed. Next, the signal from which the spurious signal has been removed is frequency-converted by the first mixer 24 to obtain the first signal.
Is obtained. The output signal of first mixer 14 is provided to first AGC circuit 316. First
AGC circuit 316 amplifies a given signal with a gain according to control voltage Cont2, and amplifies the amplified signal to a second
Is output to the mixer 18. Further, frequency conversion is performed by the second mixer 18, and a signal of the second intermediate frequency is obtained.

Then, according to the control voltage Cont1,
By the second AGC circuit 20 'whose gain is determined,
The level of the output signal of the second mixer 18 is adjusted, and the level-adjusted signal is output to the quadrature demodulation unit 22. The quadrature demodulation unit 22 distributes the output signal of the oscillator (not shown) into two signals, shifts the phase of one of the signals by 90 °, generates two mutually orthogonal signals, and uses these signals. And demodulates the signal provided by the AGC circuit 20 'to obtain a complex baseband signal (I signal and Q signal).
Get.

The gain characteristics of the first AGC circuit 316 and the second AGC circuit 20 'according to this embodiment are almost the same as those of the fifth embodiment. Here, FIG.
In FIG. 5, the horizontal axis represents the magnitude of the control voltage Cont1, but in the present embodiment, the horizontal axis is changed to an input signal level such that the magnitude becomes smaller as going to the right. I just need.

Therefore, in the sixth embodiment, as in the fifth embodiment, when the input level is -40 dBm, which is the maximum, as in the first embodiment,
The maximum input level of the AGC circuit can be taken higher, while the input level becomes the minimum -102 dBm.
In this case, it is possible to secure a sufficient noise figure NF. Here, in FIG. 16C, the control voltage Cont1
Is the horizontal axis, but in the present embodiment,
The input signal level may be changed such that the magnitude decreases as the horizontal axis advances to the right.

According to this embodiment, even when the portable telephone on which the receiving circuit is mounted is operated at a low voltage and the current consumption is suppressed low, when the input signal is small, When the input signal is large, a sufficient maximum allowable input level can be secured while maintaining good noise characteristics.

Next, the configuration of a telephone using the receiving circuits according to the first to sixth embodiments and an example in which a control voltage is set based on a signal given to an antenna will be described. Add a description.

FIG. 18 is a block diagram schematically showing a GSM type portable telephone using the receiving circuits according to the first to sixth embodiments. In this figure, the number 800 is assigned to the receiving circuit, but this may be any of the receiving circuits according to the first to sixth embodiments. As shown in FIG. 18, the cellular phone receives a signal shaping unit 8 that receives an I signal and a Q signal output from the receiving circuit and shapes the waveform in addition to the receiving circuit 800.
01, a baseband serial interface 802 for performing processing for obtaining a baseband signal from the signal obtained by the signal shaping unit 801, and a control signal generating unit having a digital / analog (D / A) converter 803
And a PLP 804 that receives digital data from the baseband serial interface 802 and executes processes such as waveform equalization, code expansion decoding, and audio decoding based on the data, and an antenna 805 that receives external radio waves. I have. Further, a D / A converter, an amplifier, a speaker, a transmission circuit, and the like for converting the audio data obtained by the PLP 804 into an analog signal are provided in this mobile phone, but these are omitted in the drawings. I have.

Control signal generating section 803 receives data indicating the IQ amplitude level from baseband serial interface 802, and based on the data, changes the value of the control signal so that the AGC circuit outputs a signal of a predetermined amplitude. After the determination, the control signal is supplied to the AGC circuit via the D / A converter.

The signal received by antenna 805 is applied to receiving circuit 800, where I signal and Q signal are obtained. The I signal and the Q signal are supplied to the baseband serial interface 802 via the signal shaping unit 801. In this baseband serial interface, the electric field intensity of a radio wave received by the antenna is calculated, and data relating to the IQ amplitude is output to the control signal generator 803. The control signal generator 803 obtains a control voltage based on the provided data, and outputs the control voltage Cont1 to the receiving circuit via the D / A converter.

Next, of the above-described embodiments, the first,
The signal applied to the antenna 805 (see FIG. 18) of the mobile phone according to the second and fifth embodiments will be described. FIG. 19 is a diagram illustrating an example of a signal provided to the receiving circuits according to the first, second, and fifth embodiments. As shown in FIG. 19, in GSM, about 4.6
In one frame of ms, eight data are multiplexed in a time division manner. For example, the first burst 190 in FIG.
1 indicates reception (Rx), third burst 1902 is transmission (Tx), and fourth and fifth bursts 1
Reference numerals 903 and 1904 denote monitors (Mo). In FIG. 19, all bursts are arranged in series in the same frame for convenience of description, but actually, the reception burst (Rx) and the transmission burst (Tx)
And the monitor burst (Mo) exist on different channels (frequency), respectively. Further, in GSM,
Since frequency hopping is performed, adjacent frames may be on different channels (frequency).

In the portable telephone, the electric field strength of the radio wave is measured by the first burst (Rx) 1901 of a certain frame. More specifically, first, the antenna 8
From 05, the electric field strength of the radio wave is measured based on the signal obtained through the receiving circuit and the signal shaping unit 801. Next, data indicating the IQ amplitude from the baseband serial interface 802 is supplied to the control signal generator 803 so that the AGC circuit of the receiver circuit has a predetermined gain, and the control voltage Cont1 based on the data is supplied to the control signal generator 803. D / of 803
Output from the A converter. .

The control voltage Cont1 is received by the first burst (Rx) 1904 of the next frame.
Based on the electric field strength, it is determined so that I and Q signals having predetermined amplitudes are obtained. The baseband serial interface 802 transmits data on the IQ amplitude,
The control signal is output to the control signal generator 803, and as a result, the control voltage Cont1 is supplied from the D / A converter of the control signal generator 803 to the AGC circuit or the like of the receiving circuit. Once determined, the control voltage Cont1 is maintained for a time corresponding to a predetermined number of frames, and the electric field strength from the base station is measured based on the first burst (Rx) of the subsequent frames.

FIG. 20 is a diagram showing an example of a signal applied to the receiving circuit according to the third embodiment. The configuration of this signal is the same as that shown in FIG. 19, but the operation of the mobile phone is different from that of the above-described embodiment.

For example, in the third embodiment,
The first burst (Rx) 2001 of a certain frame sets the electric field strength of the radio wave from the base station. When receiving in the first burst (Rx) 2002 of the next frame, the first burst (Rx) 200 of a certain frame
1, the electric field strength of the radio wave from the base station is measured.

Then, before receiving the first burst (Rx) 2002 of the next frame, according to the obtained electric field strength, the baseband serial interface 80
2, the data relating to the IQ amplitude is supplied to the control signal generating section 803, and the switching signal SW is supplied from the D / A converter of the control signal generating section 803 to the switching section 705 and the switching section 706 of the receiving circuit. Further, in accordance with the data relating to the IQ amplitude provided by the baseband serial interface 802, the control signal generation unit 803 outputs the control voltage Cont1 from the control circuit AGC of the receiving circuit so that I and Q signals having predetermined amplitudes are obtained. Provided to circuits and the like.

In the switching section 705, one of the input side and the output side is connected based on the switching signal SW. On the other hand, in the switching section 706, any one of the input sides is connected based on the switching signal SW. One and the output side are connected. As described above, the switching signal SW indicates that the control voltage has the predetermined value V4.
At the time of switching the high frequency switch 801,
It is provided to switching section 705 and switching section 706. As a result, the signal is appropriately provided to one of the variable gain amplifiers 102 and 107. Also in this embodiment, once determined control voltage Cont1 and switching signal S
W is maintained for a time corresponding to a predetermined number of frames, and the electric field strength of the radio wave from the base station is measured based on the first burst (Rx) of the subsequent frames.

In the fourth embodiment, the electric field strength from the base station is set by the first burst (Rx) 2001 of a certain frame. When receiving in the first burst (Rx) 2002 of the next frame, the electric field strength of the radio wave from the base station is measured by the first burst (Rx) 2001 of a certain frame.

Then, before receiving the first burst (Rx) 2002 of the next frame, the baseband serial signal is obtained in accordance with the obtained electric field strength so as to obtain I and Q signals having predetermined amplitudes. Interface 8
02, data relating to the IQ amplitude is supplied to the control signal generator 803. The control signal generator 803 calculates a control voltage based on the received data, and supplies the control voltages Cont1 and Cont2 via the D / A converter to the first variable gain amplifier 102 and the linearizer 104 of the AGC circuit.
Respectively. Also in this embodiment, once determined control voltages Cont1 and Cont2 are maintained for a time corresponding to a predetermined number of frames, and based on the first burst (Rx) of the subsequent frame, the electric field from the base station is determined. The intensity is measured.

Further, similarly to the fourth embodiment, in the sixth embodiment, the control voltages Cont1 and Cont2
Are provided to the first AGC circuit 216 and the second AGC circuit 20 ′, respectively.

In this manner, the control voltage, the switching signal, and the like are determined, and it becomes possible to obtain the I signal and the Q signal having the determined amplitude.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say, this is done.

For example, in the first to third embodiments, the AGC circuit according to the present invention is provided in the receiving circuit employing the double conversion method.
The present invention is not limited to this, and it is clear that the AGC circuit according to the present invention may be used in a receiving circuit employing the single conversion method shown in FIG.

In the second and third embodiments, the switching unit 705 converts the input signal (AGCin) into
Although provided to one of the variable gain amplifiers 102 and 107, the number of variable gain amplifiers is not limited to two. For example, with respect to the second embodiment, three or more variable attenuators having characteristics of mutually different attenuation amounts (absolute values of negative gain) are arranged, and one of them is switched by the switching unit. By selecting and giving a signal, and by appropriately controlling the gain of the selected variable gain amplifier, etc.,
As a whole, it is possible to obtain more specific gain characteristics for the control voltage for the AGC circuit. It goes without saying that the same applies to the third embodiment.

Further, in the first embodiment, the variable attenuator and the variable gain amplifying section are formed by the bipolar process, but the present invention is not limited to this. For example, these may be made by a CMOS process. In this case, the characteristics of attenuation (absolute value of negative gain) and gain with respect to the control voltage have a step-like shape. If these characteristics increase (or decrease) substantially monotonically, desired characteristics are obtained. The effect can be obtained. Further, it is more preferable that the gain characteristic of the entire AGC circuit is monotonous with respect to the control voltage.

In the second and third embodiments, the switching section 705 is constituted by the high frequency switch 801, and the high frequency switch 801 is configured to be controlled by the switch switching signal SW. However, the present invention is not limited to this. Here, FIG.
It is a figure showing other examples of 05. As shown in FIG. 21, the switching unit 1705 has a high-frequency switch 1801 and a switching signal generation unit 1802. High frequency switch 18
01 has one input terminal and two output terminals,
The input side and one of the two output sides are connected in accordance with the switch switching signal SW provided by the switching signal generation section 1802.

Further, switching signal generating section 1802 receives control voltage Cont1, and this control voltage Cont1 has a predetermined value V4.
At this time, a switch switching signal SW for switching the high frequency switch 1801 is output.

In the AGC circuit having the switching unit 705 thus configured, the signal (AGCin) supplied from the second mixer 18 (see FIG. 22) is supplied to the switching unit 705. This signal is supplied to one of the variable gain amplifying units 102 and 107 via the high frequency switch 801 of the switching unit 705.

Switching signal generating section 1802 of switching section 705
Receives the control voltage Cont1, and outputs a switch switching signal SW to the high-frequency switch 1801 when the control voltage is a predetermined value V4. Therefore, the variable gain amplifying units 102, 1 of the AGC circuit using such a switching unit 705
The gain characteristics of 07 correspond to the straight line 901 and the straight line 902 shown in FIG. 9, respectively. Also in this example, when the value of the control voltage Cont1 is V2 to V4, the signal (AGC) from the second mixer 18 is controlled by the high-frequency switch 801.
in) is provided to the variable gain amplifier 102, while
When the value of the control voltage Cont1 is between V4 and V1, the signal (AGCin) is given to the variable gain amplifier 107 by the high frequency switch. As a result, similarly to the third embodiment, the gain characteristic of the AGC circuit with respect to the control voltage Cont1 monotonously increases as shown by a straight line 903 in FIG. 9E. Further, the maximum allowable input level and the noise figure NF of the AGC circuit with respect to the control voltage Cont1 also correspond to the polygonal lines 1001 and 1002 in FIG.

Further, in the second and third embodiments, the switching unit 705 converts the signal (AGCin) provided from the second mixer 18 to one selected variable attenuator or fixed attenuator. Is configured to output
It is not limited to this. For example, the switching unit 70
Instead of 5, a signal distributor for distributing a given signal to a plurality of signals is arranged, and the signal (AGCin) is supplied to a variable attenuator or a fixed attenuator connected to the output side of the signal distributor. And a signal adder for adding an output signal from the variable gain amplifying unit may be arranged instead of the switching unit 706. In this case, the length of each signal path from the signal distributor to the signal adder is appropriately set (for example, λ / 4), and the second embodiment or the third embodiment is used. In the embodiment, by turning off the power supply of the variable gain or fixed attenuator and the variable gain amplifier on the side not selected by the switching unit 705, the AGC circuit is different from that of the second or third embodiment. It operates similarly and can obtain substantially the same effect. This is because the impedance of the non-selected path is negligible, so that a certain path is selected and a current flows.

Further, the variable attenuator used in the first and second embodiments may be an element having a negative gain, such as a variable resistance attenuator.

Further, in the above embodiment, AG
In the C circuit, an output amplifier is arranged after the variable gain amplifier in order to keep the output saturation point constant, but it is clear that omitting these does not affect the effect of the present invention at all. It is.

In the above embodiment, the variable gain amplifying sections 102 and 107 are provided with a plurality of differential amplifiers 10.
2-1 to 102-n and 107-1 to 107
−n, but the number of differential amplifiers may be determined according to the required gain.

Further, in the second embodiment, the differential amplifier 102 honoring the variable gain amplifying sections 102 and 107
-1 to 102-n and 107-1 to 107-
n is a digital circuit composed of CMOS transistors, the gain of which is digitally changed. In this case, the gain characteristic of the finally obtained AGC circuit with respect to the control voltage may be stepped.
Therefore, the variable gain amplifiers 102 and 107 are configured so that the gains of the first-stage differential amplifiers can be changed in an analog manner. As a result, the gain characteristic of the entire AGC circuit with respect to the control voltage can be smoothly and monotonically increased or decreased. Further, with this configuration, the number of circuit elements can be reduced.

In the above embodiment, the GSM
Although the receiving circuit of the mobile phone adopting the system has been described, the present invention is not limited to this.
It is clear that the AGC circuit and the receiving circuit according to the present invention can be applied to a 1800 mobile phone, a PCS1900 mobile phone, and the like.

Further, in this specification, the function of one means or member may be realized by two or more physical means or members, or the function of two or more means or members may be realized by one means or It may be realized by a member.

[0133]

According to the present invention, by providing another variable gain amplifying section in the AGC circuit before the normal variable gain amplifying section, when the gain of the conventional AGC circuit is reduced, the maximum allowable input level is reduced. Characteristics that were small can be increased. Thus, when the gain of the AGC circuit decreases, the gain of another variable gain amplifying unit can be reduced (for example, attenuated) in the preceding stage, and the maximum allowable input level can be increased.

Further, according to the present invention, another variable gain amplifying section is provided in parallel with the normal variable gain amplifying section in the AGC circuit, and each variable gain amplifying section is switched according to the level of an input signal. Can also be. This allows AG
When the gain of the C circuit decreases, one of the variable gain amplifying units having better characteristics is selected, and as a result, the maximum allowable input level can be increased.

Further, according to the present invention, in the receiving circuit of the double conversion system, another AGC circuit is provided before the normal AGC circuit, so that the gain of the conventional AGC circuit is reduced. The problem that the maximum allowable input level could not be increased can be solved.

Further, by forming a receiving circuit using the AGC circuit of the present invention, a mobile phone terminal with high sensitivity and low power consumption can be realized.

That is, according to the present invention, it is possible to provide an automatic gain control circuit for a cellular phone which has reduced current consumption and improved reception sensitivity, and a receiving circuit using the same. I without impairing its performance
It is possible to provide an automatic gain control circuit and a receiving circuit that can be converted to C. As a result, the sensitivity is good, and
A mobile phone with low power consumption can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an AGC circuit according to a first embodiment of the present invention.

FIG. 2 is a graph illustrating a gain characteristic with respect to a control voltage of the AGC circuit according to the first embodiment;

FIG. 3 is a graph illustrating a noise figure and a maximum allowable input level with respect to a control voltage of the AGC circuit according to the first embodiment;

FIG. 4 is a block diagram illustrating a configuration of an AGC circuit according to a second embodiment of the present invention.

FIG. 5 is a graph illustrating a gain characteristic with respect to a control voltage of the AGC circuit according to the second embodiment;

FIG. 6 is a graph illustrating a noise figure and a maximum allowable input level with respect to a control voltage of the AGC circuit according to the second embodiment.

FIG. 7 is a block diagram of an AGC circuit according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a switching unit according to a third embodiment;

FIG. 9 is a graph illustrating a gain characteristic with respect to a control voltage of the AGC circuit according to the third embodiment;

FIG. 10 is an illustration of an AG according to a third embodiment;
9 is a graph showing a noise figure and a maximum allowable input level with respect to a control voltage of the C circuit.

FIG. 11 is a diagram illustrating an AG according to a fourth embodiment;
3 is a block diagram illustrating a configuration of a C circuit.

FIG. 12 is an illustration of an AG according to a fourth embodiment;
5 is a block diagram illustrating a configuration of a receiving circuit using a C circuit.

FIG. 13 is an illustration of an AG according to a fourth embodiment;
9 is a block diagram illustrating a configuration of another receiving circuit using a C circuit.

FIG. 14 is a block diagram illustrating a configuration of a receiving circuit according to a fifth embodiment;

FIG. 15 is a first embodiment according to the fifth embodiment;
Characteristics of the AGC circuit with respect to the control voltage and the second
6 is a graph showing gain characteristics with respect to a control voltage of the AGC circuit of FIG.

FIG. 16 is a diagram illustrating a first embodiment according to the fifth embodiment;
9 is a graph showing the noise figure NF and the maximum allowable input level of the AGC circuit and the second AGC circuit of FIG.

FIG. 17 is a block diagram illustrating a configuration of a receiving circuit according to a sixth embodiment;

FIG. 18 is a block diagram schematically showing a mobile phone using the receiving circuits according to the first to sixth embodiments.

FIG. 19 is a diagram illustrating an example of a signal provided to the receiving circuit according to the present invention.

FIG. 20 is a diagram illustrating an example of a signal provided to the receiving circuit according to the present invention.

FIG. 21 is a diagram illustrating another example of the switching unit according to the third embodiment;

FIG. 22 is a diagram illustrating an example of a reception circuit including an AGC circuit.

FIG. 23 is a diagram illustrating another example of a receiving circuit having an AGC circuit.

FIG. 24 is a block diagram showing a configuration of a conventional AGC circuit.

FIG. 25 is a graph showing an example of a gain characteristic with respect to a control voltage of a conventional AGC circuit.

FIG. 26 is a graph showing an example of a noise figure and a maximum allowable input level with respect to a control voltage of a conventional AGC circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Receiving circuit 12 Front end part 14 1st mixer 16 Intermediate frequency amplifying part 18 2nd mixer 20 Automatic gain control amplifier (AGC circuit) 22 Quadrature demodulation part 101 Variable attenuation part 102-1-102-n Variable gain amplifying part 103 output amplifier 104 linearizer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04L 27/14 H04L 27/14 B

Claims (20)

[Claims] An automatic gain control amplifier for amplifying an input signal with a gain determined according to a control signal so that the amplitude of the input signal is substantially constant irrespective of the amplitude of the input signal. An attenuating unit, a variable gain amplifying unit connected to the variable attenuating unit and receiving an output of the variable attenuating unit, based on the control signal, a negative gain and a gain of the variable attenuating unit and the variable gain amplifying unit, Gain control signal generating means for generating a first gain control signal and a second gain control signal for controlling each of them, and providing these to the variable attenuator and the variable gain amplifier, respectively. The input signal received by the variable attenuator is attenuated according to the first gain control signal and the second gain control signal, and is output from the variable attenuator. The variable gain amplifying unit is configured to amplify a signal received by the variable attenuating unit, such that the absolute value of the negative gain of the variable attenuating unit with respect to the control signal increases as the input signal increases. An automatic gain control amplifier, wherein the gain of the variable gain amplifying unit with respect to the control signal decreases as the absolute value of the negative gain increases. 2. The variable attenuator is configured such that the characteristic of the negative gain with respect to the control signal changes substantially monotonically and substantially continuously, and the variable gain amplifying unit adjusts the gain of the control signal with respect to the control signal. 2. The automatic gain control amplifier according to claim 1, wherein the characteristic is changed substantially monotonically and substantially continuously. 3. The variable gain section has a characteristic of a negative gain with respect to the control signal, which is substantially monotonic and substantially continuous except at least at a discontinuous point, and the control signal of the variable gain amplifying section. 2. The automatic gain control amplifier according to claim 1, wherein a gain characteristic of the automatic gain control amplifier is substantially monotonic and substantially continuous except at least at a discontinuous point. 4. The variable attenuator and the variable gain amplifier, wherein the sum of a negative gain characteristic of the variable attenuator with respect to the control signal and a gain characteristic of the variable gain amplifier with respect to the control signal is obtained. The first gain control signal and the second gain control signal are generated by the gain control signal generating means so as to be substantially monotonous and linear, and the negative 4. The automatic gain control amplifier according to claim 2, wherein a gain characteristic and a gain characteristic of the variable gain amplifying unit are determined. 5. The temperature dependence of a characteristic of a negative gain of the variable attenuator with respect to the control signal is opposite to a temperature dependence of a characteristic of a gain of the variable gain amplifier with respect to the control signal. 5. The variable gain amplifier according to claim 2, wherein a sum of a negative gain characteristic of said variable attenuator and a gain characteristic of said variable gain amplifier has no temperature dependency. The automatic gain control amplifier according to claim 1. 6. The gain control signal generating means such that the maximum allowable input level capable of maintaining linearity in the automatic control gain amplifier increases as the gain of the automatic control gain amplifier decreases. And generating a first gain control signal and a second gain control signal to be provided to the variable attenuator and the variable gain amplifying unit. Gain control amplifier. 7. An automatic gain control amplifier for amplifying an input signal with a gain determined according to a control signal so that the amplitude is substantially constant irrespective of the amplitude of the input signal. Switching means having at least a plurality of outputs and providing an accepted signal to at least a selected one of the plurality of outputs, each connected to one of the plurality of outputs of the switching means. And at least a plurality of attenuators for receiving one of the outputs thereof; a variable gain amplifying unit connected to each of the plurality of attenuators; and a control signal for receiving and controlling the plurality of variable gains based on the control signal. Gain control signal generating means for generating a plurality of gain control signals for controlling the gains of the amplifying sections, and providing these to the plurality of variable gain amplifying sections, respectively, On the output side, an output signal from one of the variable gain amplifying units connected via one of the attenuators is substantially monotonic and substantially continuous except for at least the discontinuous point according to the change of the control signal. An output side is selected by the switching means so as to change, and a gain of the selected one of the plurality of variable gain amplifying sections with respect to the control signal is determined. Automatic gain control amplifier. 8. An output side is selected by said selection means such that an output signal from a selected one of said variable gain amplifiers changes substantially monotonically and substantially continuously according to a change in said control signal. 8. The automatic gain control amplifier according to claim 7, wherein a gain of the selected one of the plurality of variable gain amplifying units with respect to the control signal is determined. 9. The automatic gain control amplifier according to claim 7, wherein each of the plurality of attenuators comprises a fixed attenuator having a different attenuation. 10. Each of the plurality of attenuators receives another gain control signal generated by the gain control signal generating means, and attenuates the received signal by an amount of attenuation according to the other gain control signal. 9. The variable attenuator according to claim 7, wherein each of the plurality of attenuators has a characteristic of an amount of attenuation with respect to the other gain control signal so as to be different from each other. Automatic gain control amplifier. 11. The attenuator according to claim 1, wherein the plurality of attenuators include a first attenuator connected to one output side of the switching means and a second attenuator connected to the other output side of the switching means. Wherein the plurality of variable gain amplifying sections are composed of a first variable gain amplifying section connected to the first attenuator, and a second variable gain amplifying section connected to the second attenuator. Wherein the gain control signal generating means receives the control signal and controls a gain of the first variable gain amplifier and a gain of the second variable gain amplifier based on the control signal. The apparatus according to claim 1, wherein a gain control signal and a second gain control signal are generated and supplied to the first variable gain amplifying unit and the second variable gain amplifying unit, respectively. Item 11. Automatic gain according to any one of Items 7 to 10. Your amplifier. 12. The gain control signal generating means according to claim 1, wherein the maximum allowable input level capable of maintaining the linearity in the automatic control gain amplifier increases as the gain of the automatic control gain amplifier decreases. And generating a gain control signal to be supplied to each of the plurality of variable gain control means and / or another gain control signal to be supplied to the plurality of attenuators.
2. The automatic gain control amplifier according to claim 1. 13. At least a plurality of input sides, each connected to one of the plurality of variable gain amplifying sections,
A variable gain amplifier connected to the output side selected by the first switching means via the attenuator, the second switching means having one output side; The automatic gain control according to any one of claims 7 to 12, wherein one of the plurality of input sides is connected to an output side so as to select an output from the automatic gain control section. amplifier. 14. The power supply of an attenuator and a variable gain amplifying unit other than the attenuator and the variable gain amplifying unit connected to an output side selected by the switching unit is turned off. 14. The method according to claim 7, wherein:
An automatic gain control amplifier according to any one of the preceding claims. 15. A receiving circuit using the automatic gain control amplifier according to any one of claims 1 to 14, wherein the receiving circuit receives a signal from an antenna, amplifies the signal, and extracts only a receiving band. A front end unit, a first mixer that receives an output signal from the front end unit and converts the output signal into a signal of a first intermediate frequency;
An amplifier for receiving and amplifying an output from the first mixer, and a second mixer for receiving an output signal from the amplifier and converting the output signal into a signal of a second intermediate frequency; The automatic gain control amplifier receives a control signal determined based on a reception strength of a signal from the antenna, receives an output signal from the second mixer, and outputs an output signal from the second mixer. A receiving circuit configured to amplify with a gain according to a control signal, and further comprising a quadrature demodulation unit that receives an output signal from the automatic gain control amplifier and demodulates the received signal. 16. A receiving circuit using the automatic gain control amplifier according to claim 1, which receives a signal from an antenna, amplifies the signal, and extracts only a receiving band. A front end unit, and a mixer that receives an output signal from the front end unit and converts the output signal into a signal of a first intermediate frequency;
The automatic gain control amplifier receives a control signal determined based on a reception strength of a signal from the antenna, receives an output signal from the second mixer, and outputs an output signal from the second mixer. A receiving circuit configured to amplify according to a control signal, and further comprising a quadrature demodulation unit for receiving an output signal from the automatic gain control amplifier and demodulating the received signal. 17. A front end unit for receiving a signal from an antenna, amplifying the signal, and extracting only a reception band, receiving an output signal from the front end unit, and converting the output signal to a first intermediate frequency. And a variable gain amplifier that receives an output from the first mixer and amplifies the received signal with a gain according to a first control signal. A second mixer for accepting the output signal and converting it to a signal of a second intermediate frequency; and accepting the output signal from the second mixer and gaining it according to the second control signal, An automatic gain control amplifier for amplifying the received signal, a quadrature demodulation unit for receiving an output signal from the automatic gain control amplifier and demodulating the received signal, and an electric field of a signal from the antenna Gain control signal generation means for determining the first control signal and the second control signal based on the intensity, wherein the gain control signal generation means adjusts the variable gain as the electric field intensity increases. A receiving circuit configured to generate the first control signal and the second control signal such that gains of the amplifier and the automatic gain control amplifier are reduced. 18. A front end unit for receiving a signal from an antenna, amplifying the signal, and extracting only a reception band, receiving an output signal from the front end unit, and converting the output signal to a first intermediate frequency. And a variable gain amplifier that receives an output from the first mixer and amplifies the received signal with a gain according to a first control signal. A second mixer for accepting the output signal and converting it to a signal of a second intermediate frequency, and accepting the output signal from the second mixer and gaining it according to the first control signal, An automatic gain control amplifier for amplifying the received signal, a quadrature demodulation unit for receiving an output signal from the automatic gain control amplifier and demodulating the received signal, and an electric field of a signal from the antenna Gain control signal generation means for determining the first control signal based on the intensity, wherein the gain control signal generation means includes a variable gain amplifier and an automatic gain control amplifier, A receiving circuit configured to generate the first control signal such that a gain is reduced. 19. The gain control signal generating means according to claim 1, wherein said variable gain amplifier and said automatic gain control amplifier have a characteristic that said gain with respect to said electric field intensity is substantially monotonous and continuous. 19. The receiving circuit according to claim 17, wherein the receiving circuit generates a signal and / or the second control signal. 20. A mobile phone, comprising: the receiving circuit according to claim 15; and a transmitting circuit.