JP2002026751A - Variable tuning filter control method and receiver using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver that can apply frequency tuning control to a variable tuning filter, by utilizing a frequency control signal of a PLL local oscillation circuit. SOLUTION: An amplifier 1 amplifies a received signal 101 up to a desired amplitude. The variable tuning filter 2, that is controlled by a voltage control signal 110 applies band limiting to the received signal 101. A mixer 3 applies frequency conversion to the received signal 101. An intermediate frequency amplifier 4 amplifies the output of the mixer 3, until it has a desired amplitude. A filter 5 eliminates unwanted waves which lie outside of the band. A demodulation section 6 demodulates an output of the filter 5. A local oscillation section 7 provides the output of a local oscillation signal 104, on the basis of the frequency control signal 106. A digital/analog converter 8 supplies the voltage control signal 110, selected from a preset control voltage corresponding to the frequency control signal 106, to the variable tuning filter 2. A control section 9 outputs the frequency control signal 106, on the basis of an external control signal 105 that designates the frequency of the received signal 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide band receiving apparatus, and more particularly, to a frequency tuning control of a tunable filter,
The present invention relates to a receiving device that can perform the operation using a frequency control signal of an LL local oscillation circuit.

[0002]

2. Description of the Related Art A wide band receiving apparatus of this kind has a problem that a frequency band of a received signal is more than twice an intermediate frequency.
If a wideband filter having the same frequency band as the reception signal is used as the reception filter, there is a problem that the image interference wave generated by the reception mixer is generated in the band and cannot be suppressed.

In order to solve this problem, a relatively narrow band tunable filter capable of changing the center frequency in synchronization with the frequency of a received signal is provided, or a plurality of relatively narrow band filters are provided to change the received frequency. For example, there is a method of switching a filter each time the operation is performed.

In general, since providing a plurality of band filters increases costs, a tunable filter having a relatively narrow band capable of changing a center frequency in synchronization with a frequency of a received signal by a voltage control signal is used. At the same time, as a local oscillation frequency signal of the reception mixer, a PLL oscillation circuit whose output frequency can be varied by a frequency control signal in order to secure a wide frequency band is often employed.

However, since the voltage control signal for controlling the center frequency of the tunable filter cannot be simply obtained from the frequency control signal for controlling the output frequency of the PLL oscillation circuit, a control signal must be created and controlled for each. There is a problem that must be.

[0006]

In the above-mentioned conventional wideband receiving apparatus, when performing frequency tuning control of a tunable filter in accordance with the frequency setting of a received signal, a voltage control signal for controlling the center frequency of the tunable filter is provided. And a frequency control signal for controlling the local oscillation frequency of the output of the PLL oscillation circuit.

An object of the present invention is to eliminate such a conventional drawback by providing a voltage control signal for controlling the center frequency of a tunable filter, wherein a voltage control signal used for setting a local oscillation frequency of a PLL oscillation circuit output is used. By selecting a voltage control value prepared in advance by using a part, the setting of the local oscillation frequency and the setting of the center frequency of the variable tuning filter can be performed simultaneously with only the frequency control signal, and the desired wave signal can be selected and received well. A receiving device is provided.

[0008]

SUMMARY OF THE INVENTION A tunable filter control method according to the present invention is directed to a wide band receiving apparatus that limits the frequency band of an input received signal, converts the frequency using a local oscillation signal, and then demodulates the signal. The center frequency of the variable tuning filter that is the band limiting unit is set by associating a frequency control signal supplied to the local oscillation unit that generates the local oscillation signal with a voltage control signal that controls the center frequency of the variable tuning filter. Accordingly, the local oscillation signal is controlled following a change in frequency based on an external control signal.

A method of controlling a tunable filter according to the present invention is characterized in that, in a wide band receiving apparatus for performing band limitation on a frequency band of an input received signal, frequency conversion using a local oscillation signal, and demodulation, The center frequency of the tunable filter controls the frequency control signal supplied to the PLL (phase locked loop) local oscillating means using a pulse swallow method for generating the local oscillation signal and the center frequency of the tunable filter. By setting in association with a voltage control signal, control is performed following a change in the frequency of the local oscillation signal based on an external control signal.

The receiving apparatus according to the present invention performs frequency conversion by using a local tuning signal and a tunable filter whose center frequency is changed by a voltage control signal while limiting the frequency band of an input received signal. A mixer, a filter for removing unnecessary waves from the mixer output,
A demodulation unit that demodulates the filter output and outputs a demodulated signal; a local oscillation unit that is controlled by a frequency control signal to output the local oscillation signal; and a frequency of the reception signal is based on a specified external control signal. A control unit that outputs a frequency control signal; and a D / A conversion circuit that inputs the frequency control signal and supplies the voltage control signal corresponding to the frequency control signal to the tunable filter. And

The local oscillation section receives a reference oscillator for outputting a reference frequency, a voltage-controlled oscillator controlled by a phase error voltage to output the local oscillation signal, and a part of the output of the voltage-controlled oscillator. A two-modulus prescaler and a programmable N / A counter for dividing the frequency based on the division ratio data of the frequency control signal, a phase comparator for comparing the phase of the frequency-divided signal with the output of the reference oscillator, And a loop filter for inputting a comparator output and supplying the phase error voltage to the voltage controlled oscillator.

The D / A conversion circuit receives the frequency control signal output from the control unit, and stores a shift register that stores the frequency division ratio data of the frequency control signal. It is characterized by comprising a latch circuit for holding frequency ratio data, and a control voltage selection circuit for outputting the voltage control signal corresponding to the frequency division ratio data output from the latch circuit.

The control voltage selection circuit may further include a plurality of frequency division ratio data corresponding to a plurality of frequencies specified in a reception frequency band and the voltage control signal for controlling a center frequency of the tunable filter. It has a conversion table created in association therewith, and selects the voltage control signal corresponding to the frequency division ratio data output from the latch circuit and supplies the selected voltage control signal to the variable tuning filter.

Further, the frequency control signal is serial data comprising the frequency division ratio data, a clock signal and a strobe signal.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the receiving apparatus of the present invention.

In the present embodiment shown in FIG. 1, an amplifier 1 amplifies an input received signal 101 to a desired amplitude, a frequency band of the received signal 101 is limited, and a center frequency thereof is controlled by a voltage control signal 110. A variable tunable filter 2, a mixer 3 for frequency conversion using the local oscillation signal 104, and an intermediate frequency signal 10 output from the mixer 3
An intermediate frequency amplifier 4 for amplifying 2 to a desired amplitude, a filter 5 for removing unnecessary waves outside the band from the output of the intermediate frequency amplifier 4, a demodulation unit 6 for demodulating the output of the filter 5 and outputting a demodulated signal 103, A local oscillation unit 7 that is controlled by a frequency control signal 106 to output a local oscillation signal 104; and an external control signal 105 in which the frequency of the reception signal 101 is specified
A control unit 9 that outputs a frequency control signal 106 based on
The D / A converter 8 receives the frequency control signal 106 and supplies a voltage control signal 110 corresponding to the frequency control signal 106 to the tunable filter 2.

Next, the configuration of the local oscillator will be described with reference to FIG.

The local oscillator 7 receives a reference oscillator 14 that outputs a reference frequency, a voltage-controlled oscillator 11 that outputs a local oscillation signal 104 controlled by a phase error voltage, and a part of the output of the voltage-controlled oscillator 11. Frequency control signal 106
A two-modulus prescaler 15 and a programmable N / A counter 16 for frequency division based on the frequency division ratio data 107, a phase comparator 13 for comparing the phase of the frequency-divided signal with the output of the reference oscillator 14, Vessel 1
A loop filter 12 receives three outputs and supplies a phase error voltage to a voltage controlled oscillator 11.

Further, the configuration of the D / A conversion circuit will be described with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of the D / A conversion circuit shown in FIG.

The D / A conversion circuit 8 receives the frequency control signal 106 output from the control unit 9 and
Shift register 2 storing frequency division ratio data 107 of 06
1, a latch circuit 22 for holding the frequency division ratio data 107 stored by the strobe signal 109 of the frequency control signal 106, and the respective frequency division ratio data 107 corresponding to a plurality of frequencies specified in advance in the reception frequency band. , And a conversion table created by associating a voltage control signal 110 for controlling the center frequency of the tunable filter 2 with the frequency division ratio data 107 output from the latch circuit 22.
And a control voltage selection circuit 23 for selecting the voltage control signal 110 corresponding to the control signal and supplying it to the tunable filter 2.

The method of controlling the tunable filter 2 having the above-described configuration uses a part of the frequency control signal 106 supplied to the two-modulus prescaler 15 and the programmable N / A counter 16 that constitute the local oscillation unit 7. This is performed by supplying a voltage control signal 110 for selecting and outputting a preset control voltage value corresponding to the cycle ratio data 107 to the variable tuning filter 2. Therefore, there is no need to create the voltage control signal 110 dedicated to the tunable filter 2, and the desired signal can be selectively received only by setting the frequency of the external control signal 105 in which the frequency of the received signal 101 is specified.

Next, the operation of the receiving apparatus according to the present embodiment will be described in detail with reference to FIGS.

The amplifier 1 amplifies the input received signal 101 to a desired amplitude and outputs it to the tunable filter 2.

The tunable filter 2 includes a D / A conversion circuit 8
The center frequency of the pass band is controlled by the voltage control signal 110 supplied from the controller, and unnecessary wave components outside the pass band are removed.

The mixer 3 converts the received signal 101 output from the tunable filter 2 into an intermediate frequency signal 102 based on the local oscillation signal 104 output from the local oscillator 7.

The intermediate frequency amplifier 4 amplifies the intermediate frequency signal 102 output from the mixer 3 to a desired amplitude.

The filter 5 is a fixed frequency filter having a pass band of the frequency band of the intermediate frequency signal 102.
Unwanted wave components outside the pass band generated by the mixer 3 and the intermediate frequency amplifier 4 are suppressed.

The demodulator 6 demodulates the intermediate frequency signal 102 converted by the mixer 3 into an audio signal or the like.
03 is output.

The control unit 9 receives an external control signal 105 in which the frequency of the received signal 101 is specified, and
A frequency control comprising a clock signal 108 and a strobe signal 109 in addition to frequency division ratio data 107 obtained from a ratio of the frequency of the local oscillation signal 104 obtained by adding and subtracting the frequency of the intermediate frequency signal 102 to and from the reference frequency of the reference oscillator 14 The signal 106 is output.

The local oscillation section 7 is a PLL oscillation circuit using a pulse swallow method, and uses the output frequency of the reference oscillator 14 or the frequency divided by a frequency divider (not shown) as a reference frequency, a two-modulus prescaler 15 and a programmable oscillator. When the frequency division ratio data 107 for controlling the N / A counter 16 is set, the voltage controlled oscillator 1
1, the frequency of the local oscillation signal 104 can be varied, and the signal can be phase-synchronized with the reference frequency to obtain a stable signal.

The D / A conversion circuit 8 generates a local oscillation signal 104
And a conversion table created by associating the frequency division ratio data 107 for controlling the frequency of the variable control signal 2 with the voltage control signal 110 for controlling the center frequency of the pass band of the tunable filter 2.
By presetting control voltage values corresponding to the frequencies of the plurality of reception signals 101 used in the reception frequency band, the corresponding voltage control signal 110 is selected and variable when the frequency division ratio data 107 is input. Supply to tuning filter 2.

Next, the control operation of the tunable filter according to this embodiment will be described.

The receiving frequency band in mobile communication is 14
A description will be given of an example of an FM receiver from 2 MHz to 170 MHz. Assuming that the intermediate frequency is, for example, 21.4 MHz with respect to this reception frequency band, when the local oscillation frequency is set below the reception frequency, a frequency band from 120.6 MHz to 148.6 MHz is required.

Here, when the frequency to be received is determined within the range of the reception frequency band 142 MHz to 170 MHz, the local oscillation section 7 sets the phase comparison frequency of the phase comparator 13, the division ratio of the two modulus prescaler 15, the programmable N The frequency division ratio of each counter of the / A counter 16 or the number of bits of the frequency division ratio data 107 is determined. At this time, in determining the respective constants, the phase comparison frequency of the phase comparator 13 is made as high as possible, the frequency division ratio data 107 for controlling the frequency division ratio of the programmable N / A counter 16 and the local oscillation signal 104. Is designed to be one-to-one. This is because the lower the phase comparison frequency, the more difficult it is to realize the loop filter 12 that suppresses the phase comparison frequency component, and the case where there are two frequency division ratio data 107 for controlling the frequency of the local oscillation signal 104. This is because inconvenience occurs.

Next, the operation of each section will be described. Control unit 9
Outputs a frequency control signal 106 corresponding to the external control signal 105 when a predetermined frequency of the received signal 101 is indicated by the external control signal 105. The frequency control signal 106 includes the frequency division ratio data 107 and the clock signal 10
8 and a strobe signal 109, and are supplied to the programmable N / A counter 16 and the D / A conversion circuit 8 of the local oscillator 7.

The programmable N / A counter 16 and the two-modulus prescaler 15 divide the frequency of the local oscillation signal 104 to the phase comparison frequency by the frequency control signal 106 output from the control unit 9. here,
When the phase comparison frequency is 25 kHz, since the local oscillation frequency is in the range from 120.6 MHz to 148.6 MHz, the frequency division ratio is from “4,824” to “5,944”.
4 ". In order to obtain this frequency division ratio, if the frequency division ratio of the 2 modulus prescaler 15 is 64/65 frequency division, the frequency division ratio of the programmable N / A counter 16 is inevitably determined. Here, it is assumed that the input data of each counter constituting the programmable N / A counter 16 is 10 bits of N data and 7 bits of A data.

Further, the reception frequency band 142 MHz to 1
In the frequency range up to 70 MHz, 5 at 6.4 MHz intervals
Assuming that a wave is selected, three bits of the sixth, seventh and eighth bits counted from the beginning of the N data in the frequency division ratio data 107 are “110” and “11”.
1 "," 000 "," 001 ", and" 010 ".

The D / A conversion circuit 8 receives the frequency control signal 106 supplied from the control unit 9, selects an appropriate control voltage value from preset control voltage values, and outputs it as a voltage control signal 110. I do. As the control voltage value, 3 bits of the 6th, 7th and 8th bits of N data obtained when 5 waves in the reception frequency band are selected, "110", "111", "000", " 00
1 "," 010 "," V1 "," V2 ","
Five control voltage values consisting of V3 "," V4 ", and" V5 "are set in advance.

First, the shift register 21 stores the division ratio data 107 and the clock signal 1 in the frequency control signal 106.
08, and the frequency division ratio data 107 is stored bit by bit by the clock signal 108.

Next, the latch circuit 22 inputs the strobe signal 109 after all of the 17-bit division ratio data 107 is input to the shift register 21, and inputs the division ratio data input via the shift register 21. 107 is held.

Further, the control voltage selection circuit 23 determines that the third, sixth, seventh, and eighth bits of the N data input from the latch circuit 22 are "110" and "11".
If it is any one of "1", "000", "001", and "010", the control voltage value corresponding to the 3-bit data is set to "V1", "V2", "V3", "V4", "V". V5 "
Control signal 110 selected from the variable tuning filter 2
To supply.

Therefore, the tunable filter 2 has a D / D
The center frequency is controlled by the voltage control signal 110 supplied from the A conversion circuit 8, and the received signal 1 in a desired frequency band is
01 can be passed.

As described above, the local oscillation signal 1 is controlled by the external control signal 105 in which the frequency of the reception signal 101 is specified.
The frequency 04 and the center frequency of the tunable filter 2 can be simultaneously switched and controlled.

When changing the selection number of the reception frequency or changing the variable tuning filter 2, it is necessary to change the required number of bits of the frequency division ratio data 107 and the set number and set value of the control voltage value. Accordingly, each of them can be similarly controlled only by the external control signal 105 in which the frequency of the received signal 101 is specified.

The present invention is not limited to the above-described embodiment, but may be applied to a receiving device combining a local oscillator using a PLL system and a tunable filter, or a device requiring band limitation. it can.

[0046]

As described above, according to the tunable filter control method and the receiver using the same according to the present invention,
By setting a control voltage value for controlling the center frequency of the tunable filter corresponding to the frequency data of the frequency control signal in advance, control data dedicated to the tunable filter is created by an external control signal in which the frequency of the received signal is specified. Without setting, there is an effect that the frequency setting of the local oscillation unit and the tuning frequency setting of the variable tuning filter can be performed simultaneously.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a receiving device of the present invention.

FIG. 2 is a block diagram showing an embodiment of the D / A conversion circuit shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 amplifier 2 tunable filter 3 mixer 4 intermediate frequency amplifier 5 filter 6 demodulation unit 7 local oscillation unit 8 D / A conversion circuit 9 control unit 11 voltage controlled oscillator 12 loop filter 13 phase comparator 14 reference oscillator 15 2 modulus prescaler 16 programmable N / A counter 21 shift register 22 latch circuit 23 control voltage selection circuit 101 reception signal 102 intermediate frequency signal 103 demodulation signal 104 local oscillation signal 105 external control signal 106 frequency control signal 107 division ratio data 108 clock signal 109 strobe signal 110 voltage Control signal

Claims (7)

[Claims] 1. A wide band receiving apparatus which band-limits a frequency band of an input received signal, performs frequency conversion using a local oscillation signal, and demodulates the frequency band using a local oscillation signal. The frequency of the local oscillation signal based on an external control signal is set by associating a frequency control signal supplied to a local oscillation unit that generates a local oscillation signal with a voltage control signal that controls a center frequency of the tunable filter. A control method of a tunable filter, wherein the control method is controlled following a change. 2. A wide band receiving apparatus which band-limits a frequency band of an input received signal, performs frequency conversion using a local oscillation signal, and then demodulates the frequency band using a local oscillation signal. By setting a frequency control signal supplied to a PLL (Phase Locked Loop) local oscillation means using a pulse swallow method for generating a local oscillation signal and a voltage control signal for controlling a center frequency of the variable tuning filter in association with each other And a control method for controlling the tunable filter according to a frequency change of the local oscillation signal based on an external control signal. 3. A tunable filter for limiting a frequency band of an input received signal and changing a center frequency thereof by a voltage control signal, a mixer for performing frequency conversion using a local oscillation signal, and a mixer output. A filter for removing unnecessary waves, a demodulation unit for demodulating the output of the filter and outputting a demodulated signal, a local oscillation unit for outputting the local oscillation signal controlled by a frequency control signal, and a frequency of the reception signal designated. A control unit that outputs the frequency control signal based on the external control signal, and a D / A conversion circuit that inputs the frequency control signal and supplies the voltage control signal corresponding to the frequency control signal to the tunable filter. , A receiving device. 4. The local oscillator receives a reference oscillator that outputs a reference frequency, a voltage-controlled oscillator that is controlled by a phase error voltage to output the local oscillation signal, and a part of the output of the voltage-controlled oscillator. A two-modulus prescaler and a programmable N / A counter for dividing the frequency based on the division ratio data of the frequency control signal, a phase comparator for comparing the phase of the frequency-divided signal with the output of the reference oscillator, 4. The receiving device according to claim 3, further comprising: a loop filter that inputs a comparator output and supplies the phase error voltage to the voltage controlled oscillator. 5. The D / A conversion circuit receives the frequency control signal output from the control unit, and stores a shift register that stores the frequency division ratio data of the frequency control signal. 4. A latch circuit for retaining frequency ratio data, and a control voltage selection circuit for outputting the voltage control signal corresponding to the frequency division ratio data output from the latch circuit. Or the receiving device according to 4. 6. The control voltage selection circuit according to claim 1, wherein each of the frequency division ratio data corresponding to a plurality of frequencies specified in a reception frequency band and the voltage control signal for controlling a center frequency of the tunable filter. 4. The apparatus according to claim 3, further comprising a conversion table created in association with the voltage control signal, the voltage control signal corresponding to the frequency division ratio data output from the latch circuit being selected and supplied to the variable tuning filter.
Or the receiving device according to 5. 7. The receiving apparatus according to claim 3, wherein the frequency control signal is serial data including the frequency division ratio data, a clock signal, and a strobe signal.