JP2003332859A - Output amplifier and radio transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an output amplifier which can output a signal of a designated power level and has high power efficiency, and a radio transmitter which is provided with the output amplifier, can output the signal of the designated power level and has high power efficiency. <P>SOLUTION: This output amplifier provided with a variable gain amplifier and a power amplifier individually controls a bias current of each of amplification stages constituting the power amplifier according to the output power, and controls the gain of the variable gain amplifier as well as the bias current of each of the amplification stages constituting the power amplifier to output the signal of the designated power level. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output amplifier and a radio transmitter, and more particularly to an output amplifier capable of outputting a signal having a specified power level and having high power efficiency, and the output. The present invention relates to a wireless transmitter that includes an amplifier and can output a signal of a specified power level and that has high power efficiency.

The power level output by the transmitter, whether wireless or wireline, is the signal-to-noise ratio at the receiver input (in English, the Signal-to-Noise Ratio. It is an important design parameter that determines abbreviated S / N or SNR.) And is set to a sufficient level in consideration of the loss in the transmission line and the mixing of noise.

In particular, although the directivity of a commonly used antenna is sharp, the effect of loss due to the spread of the transmission beam, the effect of loss due to the effects of weather and obstacles, and
In the case of wireless communication in which the signal-to-noise ratio tends to decrease due to the influence of noise radio waves coexisting with signal radio waves on the wireless communication path, it is necessary to transmit at a higher output power than that of a wired transmitter. For this reason, the power consumption of the output amplifier and the wireless transmitter in the wireless communication is usually larger than the power consumption of the output amplifier and the wired transmitter in the wired communication.

Since the large power consumption is a major cause of hindering the miniaturization of the output amplifier and the radio transmitter,
Designing high power efficiency of output amplifier and wireless transmitter,
It is required to reduce the power consumption of the output amplifier and the wireless transmitter as much as possible. In particular, miniaturization is a top priority issue for hand-held type wireless transmitters and wireless transmitters mounted on mobile units. Especially for battery-powered wireless transmitters, it is necessary to minimize battery drain. In addition, it is required to design the wireless transmitter to have higher power efficiency.

Further, in mobile communication represented by a mobile phone, it is necessary to keep the power level of a signal received from a mobile station at a base station constant regardless of the distance between the mobile station and the base station. The need to keep constant regardless of the distance between the mobile and the base station basically comes from not making the dynamic range of the base station's receiving amplifier too large, but When mobile stations perform communication in the same frequency band by code division multiplexing multiple access spread spectrum communication that uses different spreading codes, eliminate the mobile station that transmits a signal with a prominent power level and move to another mobile station. There is a new need to reduce the interference to the machine and to secure the communication quality and the number of communicable channels.

Further, in order to keep the power level of the signal received from the mobile station at the base station constant irrespective of the distance between the mobile station and the base station, the transmission power of the mobile station can be variably controlled in a wide range. In addition to the above, it is necessary to be able to control with fine variable steps. In mobile communication represented by a mobile phone, the mobile unit does not move only in the area far from the base station, and the mobile unit does not continue to transmit at the maximum output. Not only that, there is a need to improve the power efficiency at low output.

Therefore, it is important to realize an output amplifier and a radio transmitter which have high power efficiency in a wide output level range and can control the output level in a wide range so that the receiving side can receive a signal at a constant power level. Has become a problem.

[0008]

2. Description of the Related Art FIG. 5 shows the configuration of a general radio transmitter.
Although detailed illustration is omitted, it is illustrated including the receiver side. In FIG. 5, 1 is a quadrature modulator that modulates I / Q signals, 2 is an intermediate frequency oscillator that supplies an intermediate frequency signal that is a carrier to the quadrature modulator 1, and 3 is a constant level control of the output of the quadrature modulator 1. The variable gain amplifier 4, 4 is a radio frequency modulator that modulates the output of the variable gain amplifier 3 into a radio frequency band, and 5 is a radio frequency oscillator that supplies a radio frequency signal as a carrier to the radio frequency modulator 4.

Further, 6 is a variable gain amplifier for controlling the level of the output of the radio frequency modulator 4, and 7 is a communication for cutting off an out-of-band signal contained in the output of the variable gain amplifier 6 and using another frequency band. Band pass filter for preventing quality deterioration of
Is a power amplifier that amplifies the output of the bandpass filter 7 to a transmission level. The variable gain amplifier 6, the bandpass filter 7 and the power amplifier 8 constitute an output amplifier.

Further, 9 is an isolator for blocking the signal reflected from the transmission output side to protect the circuit before the power amplifier 8, and 10 is a block for an out-of-band signal included in the output of the power amplifier 8, The band pass filter for preventing the deterioration of the quality of communication using the frequency band of 11, and the antenna duplexer 11 for sharing the antenna for transmission / reception or for sharing the antenna between a plurality of channels (in this case, transmission / reception It is applied for the purpose of sharing the antenna.), 12 is an antenna.

The band-pass filter 7 is used especially for the purpose of blocking out-of-band signals and suppressing unnecessary frequency components generated in the power amplifier 8, and the band-pass filter 10 is particularly used. It is used for the purpose of suppressing out-of-band signals sent to the wireless communication channel. Further, 13 is a band pass filter that limits the band of the signal received by the antenna, and 14 is a receiving unit whose details are omitted. The band pass filter 13 is used for the purpose of blocking an out-of-band signal input from the antenna and suppressing an unnecessary frequency component generated in the subsequent receiving section.

Here, the antenna duplexer 11 and the antenna 12 which are shared with the quadrature modulator 1 to the band pass filter 10 constitute a wireless transmitter, and the antenna duplexer 11 which is shared with the receiving section 14, The bandpass filter 13 and the antenna 12 constitute a wireless receiver. Figure 5
Since the configuration of 1 is a configuration of a popular wireless transmitter, the description of the wireless transmitter will be almost unnecessary, but a brief description will be given. That is, the quadrature I and Q signals are modulated by the quadrature modulator 1 by the intermediate frequency signal to be converted into a signal in the intermediate frequency band, the level is adjusted by the variable gain amplifier 3, and then the radio frequency signal is generated by the radio frequency modulator 4. Is converted into a radio frequency band signal by the variable gain amplifier 6, the level is adjusted by the variable gain amplifier 6, the out-of-band signal is cut by the band pass filter 7, the power is amplified by the power amplifier 8, and the band is passed by the band pass filter 10. Antenna 12 is a signal obtained by cutting external signals
Sent from.

Here, when controlling the transmission power in the configuration of FIG. 5, generally, the gain and bias of the power amplifier 8 are kept constant and the variable gain amplifier 6 controls the gain. Unlike the above, the power amplifier circuit (which is described with a different name from the “power amplifier” that is already used, is to match the name in the claims in the publications referred to below). ), For controlling the output power in JP-A-2001-7653.
In the publication, although not shown, “a pre-stage amplifier which is provided in a radio device and which amplifies a transmission signal, a power amplifier which amplifies a signal from the pre-stage amplifier, and an arrangement between the pre-stage amplifier and the power amplifier are provided. A first switch for switching the signal from the preamplifier to the power amplifier or through circuit;
A second switch that interlocks with the first switch to switch and output a signal from the power amplifier or a signal from a through circuit; and power control data for controlling transmission power generated based on a received signal, which is converted into a bias voltage. A bias voltage converter for controlling the bias of the power amplifier, and a switch control signal converter for converting the power control data into a switch control signal and switching the first switch and the second switch. The bias voltage conversion unit lowers the bias of the power amplifier based on the power control data, or the bias voltage conversion unit cuts off the power amplifier to stop the operation and the switch control signal. The conversion unit switches the first switch and the second switch to the through circuit side. Frequency power amplifier circuit "is disclosed.

The high-frequency power amplifier is a pre-stage amplifier for amplifying a transmission signal, a power amplifier for amplifying a signal from the pre-stage amplifier, and a signal from the pre-stage amplifier arranged between the pre-stage amplifier and the power amplifier. To the power amplifier or the through circuit, a second switch that interlocks with the first switch to switch and output a signal from the power amplifier or a signal from the through circuit, and a transmission generated based on the received signal. A bias voltage conversion unit for converting power control data for controlling power into a bias voltage to control the bias of the power amplifier; a power control data for converting the power control data into a switch control signal; A switch control signal converter for switching the second switch, and the bias voltage converter based on the power control data. Lowers the bias of the power amplifier, or cuts off the power amplifier by the bias voltage conversion unit to stop the operation, and the switch control signal conversion unit connects the first switch and the second switch to the through circuit side. The power consumption of this stage can be reduced by lowering the bias of the power amplifier or suspending the operation of the power amplifier when the transmission power is reduced. Therefore, the power consumption efficiency of the power amplifier circuit during power control can be improved.

[0015]

However, when the output power control is performed by the gain control of the variable gain amplifier 6 in the radio transmitter of FIG. 5, the following problems occur. That is, since the power amplifier 8 operates with a constant gain and bias, when the gain of the variable gain amplifier 6 is decreased to reduce the output power, the power efficiency of the power amplifier 8 decreases. In the spread spectrum communication of the code division multiple access system, the mobile device does not move only far away from the base station, and therefore it is rare that the mobile device transmits at the maximum output power in most cases. It is also often used at about%, which causes a problem that the power efficiency of the power amplifier 8 is low.

When the power efficiency of the power amplifier 8 is low, the power efficiency of the wireless transmitter is naturally low, and when operating on a battery like a mobile phone, the so-called standby time is greatly shortened, and the convenience of the mobile phone is improved. It will be greatly damaged. A technique developed to solve this problem is disclosed in Japanese Patent Laid-Open No. 2001-2001.
The technology disclosed in Japanese Laid-Open Patent Publication No. -7653,
The power amplification circuit includes a first switch arranged between the preamplifier and the power amplifier to switch a signal from the preamplifier to the power amplifier or a through circuit, and a signal from the power amplifier which is interlocked with the first switch. Alternatively, the provision of the second switch for switching and outputting the signal from the through circuit causes a new problem.

That is, when the power amplifying circuit is operating at the maximum output, or when the bias of each power amplifier is lowered and the power amplifying circuit is operating at the reduced output, the first switch. Supplies the input signal to the power amplifier of the first stage, and the second switch takes out the output of the power amplifier of the final stage. Therefore, the output signal of the power amplifier at the final stage, which has sneaked through between the two contacts of the second switch, spills through between the two contacts of the first switch, and is fed back to the input terminal of the power amplifier at the first stage. Will be done.

When the isolation between the two contacts of the first switch and the second switch is very large, the influence of the feedback signal is small, but the isolation is about 15 dB which is a practical value. In this case, the amount of feedback from the output terminal of the final stage power amplifier to the input terminal of the first stage power amplifier is -30 dB, and the gain of the power amplifier circuit is 30 dB.
If it is about dB, there is a sufficient risk that the power amplifier circuit may oscillate or the operation may become unstable.

Moreover, since the first switch and the second switch themselves have a non-negligible loss, it is necessary to correct the loss and amplify the power, and nonlinear distortion occurs in a region where the output power level is high. There is another problem of increase. In view of the above problems, the present invention is capable of outputting a signal of a specified power level, and further, an output amplifier having high power efficiency, and a signal of a specified power level including the output amplifier. It is an object of the present invention to provide a wireless transmitter that can output and has high power efficiency.

[0020]

According to a first aspect of the present invention, in an output amplifier including a variable gain amplifier and a power amplifier, the bias current of each amplification stage constituting the power amplifier is individually controlled according to the output power. In addition, the output amplifier is characterized by controlling the gain of the variable gain amplifier together with the control of the bias current of each amplification stage that constitutes the power amplifier.

According to the first aspect of the present invention, in the output amplifier including the variable gain amplifier and the power amplifier, the bias current of each amplification stage constituting the power amplifier is individually controlled, and each of the power amplifier constituting the power amplifier is controlled. Since the gain of the variable gain amplifier is controlled together with the control of the bias current of the amplification stage, it becomes possible to match the output level of the output amplifier with the designated output level.

A second invention is an output amplifier including a variable gain amplifier and a power amplifier, wherein the bias current of each amplification stage constituting the power amplifier is individually controlled according to the output power, and the power amplifier is controlled. Controlling the value of a variable resistor connected in parallel to each amplification stage constituting the power amplifier, and controlling the bias current of each amplification stage constituting the power amplifier,
And an output amplifier which controls the gain of the variable gain amplifier in accordance with the control of the value of the variable resistor.

According to the second invention, in the output amplifier including the variable gain amplifier and the power amplifier, the bias currents of the respective amplification stages constituting the power amplifier are individually controlled, and the power amplifier is constituted respectively. Controlling the value of a variable resistance connected in parallel to the amplification stage of the power amplifier, controlling the bias current of each amplification stage constituting the power amplifier, and controlling the value of the variable resistance. The gain level of the output amplifier is controlled so that the output level of the output amplifier can be matched with the specified output level. A third invention is the output amplifier according to any one of the first invention or the second invention, wherein an output power value for performing cut-off control of an amplification stage constituting the power amplifier when the output power is lowered, It is an output amplifier characterized in that it has a hysteresis with the output power for controlling conduction of the amplification stage when increasing the output power.

According to the third aspect of the invention, the output amplifier has an output power value for controlling the cutoff of the amplification stage constituting the power amplifier when the output power is lowered, and a conduction state for the amplification stage when the output power is raised. Since the output power to be controlled has a hysteresis, for example, the cut-off controlled amplification stage is not immediately returned to the conductive state, and the reliability of the output amplifier can be kept high.

A fourth invention is a radio transmitter including the output amplifier according to any one of the first to third inventions. According to the fourth invention, since the wireless transmitter includes the output amplifier according to any one of the first invention to the third invention, it becomes possible to match the output level of the transmitter with the designated output level. .

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The technique of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the output amplifier of the present invention. Although the same components as those in the configuration of FIG. 5 are denoted by the same reference numerals, all components will be described without omission so that only FIG. 1 may be referred to.

In FIG. 1, reference numeral 6 is a radio frequency modulator in the configuration of FIG. 5 (abbreviated as “RF modulator” in FIG. 1. “RF” is an abbreviation for Radio Frequency. The variable gain amplifier 7 amplifies the output of the variable gain amplifier 7 with a variable gain.
Is a band-pass filter that blocks out-of-band signals included in the output of.

Further, 8-1 and 8-2 are amplification stages constituting a power amplifier. That is, FIG. 1 illustrates an example in which the power amplifier includes two amplification stages.
Further, 8-4 and 8-5 are inserted between the power supply terminals of the amplification stages 8-1 and 8-2 and the output terminal of the voltage source Vcc to supply biases to the amplification stages 8-1 and 8-2. A current source that determines the current.

Further, 8-3 supplies a voltage for bias current control to the current sources 8-4 and 8-5 according to a transmission power instruction supplied from a circuit outside the configuration of FIG. The control unit supplies the gain amplifier 6 with a control voltage Vc for controlling the gain. The control unit 8-3 also controls the variable gain amplifier 6, but the two amplification stages 8-1 and 8-2, the control unit 8-3, and the two current sources 8 are provided.
It is assumed that the power amplifier 8 is composed of -4 and 8-5.

Here, the current sources 8-4 and 8-5 are composed of, for example, field effect transistors, the sources are connected to the output terminals of the voltage source Vcc, and the drains are respectively connected to the amplification stages 8-1 and 8. -2 is connected to the power supply terminal and the gate is connected to the control terminal (reference numeral is omitted) of the control unit 8-3, it is possible to control the current including cutoff by the gate-source voltage.

Of course, junction transistors other than field effect transistors can be used for the current sources 8-4 and 8-5. Then, the gains of the amplification stages 8-1 and 8-2 are preferably kept constant unless the currents of the current sources 8-4 and 8-5 are cut off. This can be achieved if the transfer conductance (so-called gm) in the amplification stages 8-1 and 8-2 is constant, so that the currents of the current sources 8-4 and 8-5 can be appropriately set and controlled. It can be easily realized.

Further, in the variable gain amplifier 6, the control voltage V
In order to control the gain with c, for example, the source-drain of the field effect transistor is used as a resistor, and the control voltage Vc is applied to the gate of the field effect transistor to control the resistance between the source and the drain. Then, the resistance between the source and the drain may be inserted on the drain side or the source side of the amplification stage including a field effect transistor, for example. Alternatively, the gain of the variable gain amplifier may be controlled by controlling the current flowing through the junction diode by the control voltage Vc and controlling the resistance between the anode and the cathode of the junction diode.

It is important to note that the cut-off amplification stage loses its amplification effect, and the capacitance between the input and output terminals (for example, in the case of an amplification stage composed of a field effect transistor, the gate capacitance including the wiring capacitance). Since the signal is transmitted only through the drain-to-drain capacitance), a loss is exhibited, so that when the amplification stage is cut off, the control voltage Vc in consideration of it is supplied to the variable gain amplifier 6 to amplify the gain. Immediately before and after the stage is cut off, the total gain of the variable gain amplifier and the power amplifier is kept constant.

FIG. 2 is a diagram for explaining control of output power. Further, FIG. 3 shows the relationship between the output power, the bias current of the power amplifier, and the control voltage. FIG. 3A shows the case where the output power is decreased from the maximum to the minimum.
Shows the case where the output power is increased from the minimum to the maximum. 2 and 3, the power amplifier has two amplification stages and the maximum output power is P _max (d
Bm), a method of controlling the control voltage and the bias current of the amplification stage so as to have a dynamic range of 75 dB will be described, but please pay attention to the solid polygonal line for a while.

In FIG. 2, the vertical axis represents the output of the output amplifier.
Force power, and the horizontal axis is the control power supplied to the variable gain amplifier.
It is pressure. First, from the case of maximizing the output power,
For reducing the output power to a small case
Explain. Maximum power P_maxAnd in the case, variable
The control voltage supplied to the gain amplifier is V _c1Set to 1st stage
Bias current of I₁₁To the second stage bias current_{twenty one}
Set to.

In order to reduce the output power from the state of
The control voltage supplied to the variable gain amplifier is gradually changed from V _c1 . The direction of change of the control voltage is determined by the insertion position of the variable resistor used to control the gain of the variable gain amplifier. Here, the variable resistor is inserted in the load side of the amplification stage forming the variable gain amplifier. Since it is assumed that the control voltage is increased, the control voltage is gradually decreased from V _c1 .

Then, the output power is (P_max-20) dB
When the case of m is reached, the first stage bias current
I₁₂And the bias current of the second stage is reduced to I_{twenty two}
Control voltage to V_C6I am trying. That is, the output power
Power is P_maxFrom (P_max-20) First stage up to dBm
Bias current of I₁₁To the second stage bias current _{twenty one}
Control voltage only V_C1To V_c6Dropped to
Let

From the case where the output power is set to (P _max -20) dBm to the case where the output power is set to (P _max -30) dBm, the bias current of the first stage is set to I ₁₂ , and the bias current of the second stage is set to. Change to I ₂₂ and keep, only control voltage is V _C6
Further down to V _c2 . The output power is (P
_When the case of _max -30) dBm is reached, 1
The bias current of the second stage is kept at I ₁₂ , and the bias current of the second stage is set to 0 to cut off the second amplification stage.

In order to cut off the second amplification stage, the second amplification stage loses gain and presents a loss.
When the output power is continuously set to (P _max -30) dBm or less, it is necessary to increase the gain of the variable gain amplifier to compensate the loss. Therefore, the same output power (P
_In order to secure _max- 30) dBm, the control voltage is raised from V _C2 to V _c3 .

Thereafter, the output power is (P _max -75) dBm
In order to lower the control voltage, the bias current in the first stage is kept at I ₁₂ and the bias current in the second stage is kept at 0, and only the control voltage is lowered from V _c3 to V _c4 . Then, when the control voltage becomes V _c4 , the output power is (P _max −75) dBm.
Is set to. Next, a case where the output power is increased from the case where the output power is the minimum to the case where the output power is the maximum will be described.

[0041] The output power from the case to minimize (P _max -75) dBm to cases that the output power and (P _{ma x} -30) dBm, the bias current of the first stage I _12, 2
Only the control voltage is increased from V _c4 to V _C3 while keeping the bias current of the stage at 0. When the output power is further increased from the case, the state is not changed to the case, and the state is changed to the case where the output power is (P _max -20) dBm. Therefore, when the case is reached, the bias current of the first stage is increased to I ₁₃ , and the control voltage is increased from V _c3 to V _c5 while keeping the bias current of the second stage at 0. Here, the output power (P
_max- 20) dBm must be output, so
I ₁₃ needs to be the same current as I ₂₂ .

Output power (P _max -20) dBm
When the output power is further increased after reaching the case of, the bias current of the first stage is set to I _{11 in the case.}
And increase the bias current of the second stage to I ₂₁ .
Here, since the second stage is not cut off and exhibits a gain, the control voltage is reduced from V _C5 to V _c6 to control the state.

After that, when increasing the output power from the case of the output power (P _max -20) dBm to the case of the output power P _max dBm, the bias current of the first stage is set to I _11.
And the second stage bias current is kept at I ₂₂ , and only the control voltage is increased from V _C6 to V _c1 . The above control is performed by the control unit 8-3 having the configuration shown in FIG. In the code division multiple access method, etc., the output power instruction is given from the base station to the mobile station, so the transmission power instruction is transferred to the control unit 8-3, and the power is adjusted so as to match the instructed output power. The bias current of the amplifier and the control voltage of the variable gain amplifier may be controlled. For this purpose, the control unit 8-3 has a table for storing the bias current and the control voltage with the output power as an address. When the output power is instructed, the bias current and the control voltage are read from the table and the power amplifier is used. The bias current and the control voltage of the variable gain amplifier may be controlled.

However, since the control of the bias current is different when the output power is decreased and when it is increased, it is necessary to have substantially two of the above tables, and
It is necessary to have a function of determining whether or not the instructed output power is higher than the current output power. Since it is easy for those skilled in the art to have substantially two of the above tables and to have a function of determining whether or not the instructed output power is larger than the current output power, it will be explained here. I want to omit

As described above, although the bias current of the power amplifier is kept constant between the two cases, the power consumption of the output amplifier can be continuously controlled according to the output power, so that the power consumption can be reduced. Become. In addition, it is not possible to decrease the output power from case to case and case to case, and increase the output power from case to case and case to case, that is, to provide hysteresis between cases, cases, cases and cases. That is very important.

That is, for example, even when the instruction to increase the output power slightly is issued immediately after the case transitions from case to case and the output power is slightly decreased, the current of the cut-off second amplification stage is changed. This has the advantage of not requiring frequent switching of the current source to be controlled, which is
This is because in order to increase the output power after the output power is once decreased from the case to the case direction, the output power is increased by controlling in the case direction.

In the control of the bias current associated with the control of the output power described above, an example has been described in which the bias current is kept constant between the two cases. This is because if the bias current is kept constant between the two cases, the control is simple and the data stored in the table for the control is simple. However, it is also possible to variably control the bias current according to the change in output power between the two cases. Essentially, except that the data stored in the table for control becomes slightly complicated. There is no difference from the above explanation.

When the bias current is variably controlled according to the change of the output power between the two cases, the power consumption of the output amplifier can be continuously controlled according to the output power, so that the power consumption is further reduced. It will be possible. That is,
In any case, the output amplifier described above is "independently controlling the bias current of each amplification stage constituting the power amplifier in accordance with the output power, and biasing each of the amplification stages constituting the power amplifier. It can be said to be an output amplifier that controls the gain of the variable gain amplifier together with the control of the current.

Since the bias current of each amplification stage constituting the power amplifier is individually controlled according to the output power, the power consumption of the power amplifier can be set to a value according to the output power. In addition, the power consumption of the output amplifier can be reduced. In the above description, the bias current of the second amplification stage of the power amplifier including the two amplification stages is set to 0 according to the output power. It can be set to 0 according to the output power.

In this case, when the output power is decreased from the case, when the output power is decreased from the case of FIG. 2 and the case is reached, the bias current of the second amplification stage is set to 0 and the variable gain amplifier. Then, the control voltage of the variable gain amplifier is controlled toward case b thereafter. When the case b is reached, the bias current of the first amplification stage is set to 0 to increase the control voltage of the variable gain amplifier to the case c, and thereafter, the control voltage of the variable gain amplifier is changed toward the case. Control. Similarly, when increasing the output power from the case, control is performed so as to reach the case via the case, the case d, the case e, the case f, and the case.

Therefore, in this case, the hysteresis characteristic is provided at two places. In the above description, since the diagram used in the above description in which only the bias current of the second amplification stage is set to 0 is diverted, the gain distribution of each amplification stage in the previous and current description is It should be added that they are not the same.

Further, for example, when the power amplifier is composed of three stages and the bias currents of the third amplification stage and the second amplification stage are separately set to 0, the same as in the present description. Just control. That is, the technique of the present invention can flexibly control the output power according to the form and control of the power amplifier. This also applies to the configuration of the output amplifier described below.

Furthermore, in the output amplifier shown in FIG.
Since a typical configuration in which an output amplifier is inserted between the radio frequency modulator 4 and the isolator 9 in the above configuration is assumed, the variable gain amplifier 6, the band pass filter 7 and the power amplifier 8 are used as the output amplifier. However, since it is possible to reverse the order of the variable gain amplifier 6 and the band pass filter 7, it is assumed that the output amplifier is composed of the variable gain amplifier 6 and the power amplifier 8. It is also possible. Moreover, the function of the variable gain amplifier 6 of FIG.
Since it is possible to absorb it in the design, it is not necessary to limit the output amplifier to the variable gain amplifier and the power amplifier which are directly connected.

Therefore, it can be said that the output amplifier of the present invention is essentially “provided with a variable gain amplifier and a power amplifier”. When applied to a radio transmitter, it is not necessary to arrange the output amplifier of the present invention in the subsequent stage of the radio frequency modulator, and a variable gain amplifier is arranged in front of the radio frequency modulator to perform radio frequency modulation. A power amplifier may be placed after the device.

The above also applies to the output amplifier described below. FIG. 4 shows a second embodiment of the output amplifier of the present invention. Although the same components as those in the configuration of FIG. 5 are denoted by the same reference numerals, all the components will be described without intentionally omitting them so that only FIG. 4 should be referred to here. However, some comments are omitted.

In FIG. 4, 6 is a variable gain amplifier for amplifying the output of the radio frequency modulator in the configuration of FIG. 5 with a variable gain, and 7 is a band pass filter for blocking an out-of-band signal included in the output of the variable gain amplifier 6. It is a wave instrument. Also, 8-1 and 8-
Reference numeral 2 is an amplification stage forming a power amplifier. That is, FIG. 4 also illustrates an example in which the power amplifier is composed of two amplification stages.

Further, 8-4 and 8-5 are inserted between the power supply terminals of the amplification stages 8-1 and 8-2 and the output terminal of the voltage source Vcc so that they are connected to the amplification stages 8-1 and 8-2. It is a current source that determines the bias current to be supplied. 8-6 is an amplification stage 8-1
, A diode connected in parallel between the input and output terminals of the
Is a diode connected in parallel between the input and output terminals of the amplifier stage 8-2, and 8-8 and 8-9 are choke coils that supply current to the diode 8-6 and have high impedance for high frequency signals. , 8-10 and 8-11 are choke coils that supply current to the diode 8-7 and exhibit high impedance for high frequency signals, 8
-12 is the anode of diode 8-6 and diode 8-
It is a blocking capacitor that is inserted so that the cathode of 7 does not become a short circuit in direct current but a short circuit in high frequency.

Furthermore, the current source 8-4a and the current source 8-3a are arranged in accordance with the transmission power instruction received from the circuit outside the configuration of FIG.
-5 is supplied with a voltage for controlling the bias current, and the variable gain amplifier 6 is supplied with a voltage Vc for controlling the gain.
Further, it is a control unit for supplying a voltage for controlling on / off to the diodes 8-6 and 8-7. The power amplifier 8 is constituted by the components from the amplification stage 8-1 to the blocking capacitor 8-12.

Here, the control unit 8-3a differs from the control unit 8-3 having the configuration of FIG. 1 in that diodes 8-6 and 8-7 are provided.
Is a point to supply a voltage for controlling on / off. Then, for example, when the amplification stage 8-1 to which the diode 8-6 is connected has an amplifying action, the diode 8
The voltage across both ends of −6 is made equal to control the resistance of the diode 8-6 to a sufficiently large value, and the diode 8− is connected when the amplification stage 8-1 connected to the diode 8-6 is cut off.
The ON voltage may be supplied to both ends of the diode 6 to control the resistance of the diode 8-6 to be as small as necessary.

Other than this, the configuration of FIG. 4 is essentially the same as the configuration of FIG. That is, the current sources 8-4 and 8-5 can be realized by field effect transistors or junction transistors, as in the configuration of FIG. Also, the amplification stage 8-1
The gains of 8 and 8-2 are preferably kept constant as long as the currents of the current sources 8-4 and 8-5 are not cut off, but this can be easily realized as in the configuration of FIG. is there.

In the variable gain amplifier 6, the control voltage V
Controlling the gain by c can be realized by essentially the same technique as described in the configuration of FIG. Furthermore, it is important to note that the cut-off amplification stage presents a loss,
When the amplification stage is cut off, the control voltage Vc in consideration of it is supplied to the variable gain amplifier 6.
This is because, when the amplification stage is cut off in the configuration of FIG. 1, a signal is transmitted through the capacitance between the input and output terminals of the amplification stage, while the configuration of FIG. 4 cuts off the amplification stage. In this case, the difference is that the signal is transmitted through the resistance of the diode connected between the input and output terminals of the amplification stage, and there is essentially no difference from the case of the configuration of FIG. Therefore, it can be realized by controlling the current of the amplification stage and controlling the control voltage supplied to the variable gain amplifier in accordance with this control in the same manner as shown in FIG. 2 for the configuration of FIG. .

That is, there is essentially no difference between the configuration of FIG. 4 and the configuration of FIG. However, in the configuration of FIG. 4, the resistance of the diode can be controlled in a wide range by slightly controlling the voltage supplied to both ends of the diode, so that the amplification stage to which the diode is connected is cut off. It is advantageous to the configuration of FIG. 1 that it is possible to reduce the loss at the time and to reduce the change of the control voltage supplied to the variable gain amplifier when the amplification stage to which the diode is connected is cut off. It will be a point.

In the structure shown in FIG. 4, the element connected between the input and output terminals of the amplification stage is a diode, but a structure in which the source and drain of the field effect transistor are connected between the input and output terminals of the amplification stage is also possible. . In this case, since the resistance between the source and the drain is controlled by the voltage applied to the gate, the choke coils 8-8 to 8-11 and the blocking capacitor 8-12 in FIG. It can be simplified. In particular, since the choke coil is not required, the integrated circuit can be easily integrated, and further, the characteristics of the variable gain amplifier can be prevented from deteriorating due to the stray capacitance and leakage inductance of the choke coil. . And
The change in the control voltage supplied to the variable gain amplifier can be reduced when the amplification stage to which the field effect transistor is connected is cut off, as in the case of using a diode.

That is, in the configuration of FIG. 4, "the bias current of each amplification stage constituting the power amplifier is individually controlled according to the output power, and is connected in parallel to each amplification stage constituting the power amplifier. The value of the variable resistor is controlled to control the bias current of each amplification stage constituting the power amplifier,
And the gain of the variable gain amplifier is controlled in accordance with the control of the value of the variable resistance ”.

Also in the configuration of FIG. 4, since the bias current of each amplification stage constituting the power amplifier is individually controlled according to the output power, the power consumption of the power amplifier is set to a value according to the output power. The power consumption of the output amplifier together with the power amplifier can be reduced, which is the same as the configuration of FIG. Finally, although the power amplifier in the output amplifier described above has two stages, it is not limited to two stages. However, when the power amplifier is configured in one stage, the output power required by the variable gain amplifier alone (the maximum power need not be output at this time) can be covered when the power amplifier is cut off. Note that it is necessary to carefully design the bias of the variable gain amplifier.

[0066]

As described above in detail, according to the present invention, an output amplifier capable of outputting a signal having a designated power level and having high power efficiency, and a designated power level provided with the output amplifier. It is possible to realize a wireless transmitter capable of outputting the signal of 1 and having high power efficiency.

That is, according to the first invention, in the output amplifier including the variable gain amplifier and the power amplifier, the bias current of each amplification stage constituting the power amplifier is individually controlled and the power amplifier is constructed. Since the gain of the variable gain amplifier is controlled together with the control of the bias current of each amplification stage, it is possible to match the output level of the output amplifier with the designated output level.

According to the second invention, in the output amplifier including the variable gain amplifier and the power amplifier, the bias current of each amplification stage constituting the power amplifier is individually controlled, and the power amplifier is constructed. Controlling the value of a variable resistor connected in parallel to each amplification stage, controlling the bias current of each amplification stage constituting the power amplifier, and controlling the value of the variable resistor. Controlling the gain of the gain amplifier allows the output level of the output amplifier to match the specified output level.

According to the third invention, the output amplifier is
Since a hysteresis is given to the output power value that cuts off and controls the amplification stage that constitutes the power amplifier when the output power is lowered and the output power that controls the conduction of the amplification stage when the output power is raised, for example, -It is possible to maintain the reliability of the output amplifier at a high level, because the amplification stage controlled to be off is not immediately returned to the conductive state.

Furthermore, according to the fourth aspect of the invention, since the transmitter includes the output amplifier of either the first aspect or the second aspect of the invention, the output level of the transmitter can be matched with the designated output level. Will be possible.

[Brief description of drawings]

FIG. 1 is a first embodiment of an output amplifier according to the present invention.

FIG. 2 is a diagram illustrating control of output power.

FIG. 3 shows the relationship between the output power, the bias current of the power amplifier, and the control voltage.

FIG. 4 is a second embodiment of the output amplifier of the present invention.

FIG. 5 is a configuration of a general wireless transmitter.

[Explanation of symbols]

1 Quadrature modulator 2 Intermediate frequency oscillator 3 Variable gain amplifier 4 radio frequency modulator 5 Radio frequency oscillator 6 Variable gain amplifier 7 bandpass filter 8 power amplifier 8-1 Amplification stage 8-2 Amplification stage 8-3 Control unit 8-3a Control unit 8-4 Current source 8-5 Current source 8-6 diode 8-7 diode 8-8 choke coil 8-9 Choke coil 8-10 choke coil 8-11 Choke coil 8-12 Blocking capacitor 9 Isolator 10 bandpass filter 11 antenna duplexer 12 antennas 13 bandpass filter 14 Receiver

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinichi Kawai             Hokkaido Kita-ku Kita-Shichijo Nishi 4-chome 3-1, 1               Fujitsu East Japan Digital Technology Co., Ltd.             Inside the company (72) Inventor Hirokazu Ueda             Hokkaido Kita-ku Kita-Shichijo Nishi 4-chome 3-1, 1               Fujitsu East Japan Digital Technology Co., Ltd.             Inside the company (72) Inventor Kenji Iwai             Hokkaido Kita-ku Kita-Shichijo Nishi 4-chome 3-1, 1               Fujitsu East Japan Digital Technology Co., Ltd.             Inside the company F term (reference) 5J069 AA01 AA41 CA32 CA36 CC00                       FA15 HA19 HA29 HA33 KA32                       KA44 KA53 KA68 KC04 KC06                       MA21 SA14 TA00 TA01                 5J091 AA01 AA41 CA32 CA36 FA15                       HA19 HA29 HA33 KA32 KA44                       KA53 KA68 MA21 SA14 TA00                       TA01 UW00                 5J500 AA01 AA41 AC32 AC36 AF15                       AH19 AH29 AH33 AK32 AK44                       AK53 AK68 AM21 AS14 AT00                       AT01 CC00 CK04 CK06 WU00                 5K060 CC04 DD04 HH05 HH06 JJ02                       JJ06 LL01 LL11

Claims (4)

[Claims] 1. An output amplifier including a variable gain amplifier and a power amplifier, wherein the bias current of each amplification stage of the power amplifier is individually controlled according to the output power, and each of the power amplifier is configured. An output amplifier, wherein the gain of the variable gain amplifier is controlled together with the control of the bias current of the amplification stage. 2. An output amplifier including a variable gain amplifier and a power amplifier, wherein the bias current of each amplification stage of the power amplifier is individually controlled according to the output power, and each of the power amplifier is configured. Controlling the value of a variable resistance connected in parallel to the amplification stage of the power amplifier, controlling the bias current of each amplification stage constituting the power amplifier, and controlling the value of the variable resistance. An output amplifier characterized by controlling the gain of the. 3. The output amplifier according to claim 1 or 2, wherein an output power value for performing cut-off control of an amplification stage forming the power amplifier when the output power is decreased, and an output. A radio transmitter characterized in that a hysteresis is added to output power for controlling conduction of the amplification stage when the power is increased. 4. A wireless transmitter comprising the output amplifier according to claim 1. Description: