JP2951704B2 - Interference compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for an interference compensation device for wireless communication. In particular, the present invention relates to a device that suppresses an interference wave and receives a desired signal.

[Conventional technology]

FIG. 2 is a block diagram of a conventional interference compensation apparatus.

Conventionally, the interference compensator has a configuration as shown in FIG. In FIG. 2, reference numerals 1 and 2 denote input terminals, 3 denotes an amplitude and phase control circuit, 4 denotes a signal synthesizing circuit, 5A and 5B denote signal receiving circuits composed of an amplifier, a frequency converter, a bandpass filter, and the like; Denotes a product detector, 10 denotes an interference wave compensation output terminal, and 17 denotes a 90 ° phase shifter.

A signal for normal communication is input to the input terminal 1, but an interference wave is also mixed. The input terminal 2 mainly receives an interference wave. The interference wave input to the input terminal 2 is branched into two systems. One of the signals is controlled in amplitude and phase by an amplitude / phase control circuit 3, and is combined with a signal from the input terminal 1 by a signal combining circuit 4. The synthesized signal and the other signal at the input terminal 2 are frequency-converted and amplified by the signal receiving circuits 5A and 5B, respectively, and further branched into two to be detected by the product detectors 7 and 8. At this time, one of the four signals input to the product detectors 7 and 8 is shifted by 90 ° in phase by the 90 ° phase shifter 17.
The output signals of the product detectors 7 and 8 control the amplitude and phase control circuit 3 so that the amplitude of the interference wave input from the input terminal 1 and the amplitude of the interference wave input from the input terminal 2 are the same and the phases are inverted. I do. As described above, a signal that does not include an interference wave is obtained in the output of the interference wave compensation output terminal 10.

[Problems to be solved by the invention]

However, such a conventional interference compensator requires two signal receiving circuits, and it is necessary to match the phase and amplitude fluctuation characteristics of both signal receiving circuits in order to suppress interference waves with high accuracy. For this reason, there is a drawback that there are many components and it is difficult to adjust the fluctuation of the amplitude / phase characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide an interference compensator which does not require two signal receiving circuits, has a simple configuration, and can be easily adjusted.

[Means for solving the problem]

The present invention provides a first input terminal (1) for inputting a first input signal mixed with an interference wave in addition to a desired reception wave, and a second input terminal for inputting a second input signal mainly containing the interference wave. An amplitude phase for controlling the second input signal based on an input control voltage and outputting a signal having substantially the same amplitude as the interference wave of the first input signal and having a substantially inverted phase; An interference compensator comprising a control circuit (3) and a first signal synthesizing circuit (4) for synthesizing an output signal of the amplitude and phase control circuit and the first input signal to output an interference wave compensation signal. A modulator (12) for modulating an output signal of the signal synthesizing circuit with a low-frequency signal having a lower frequency than the interference wave, and synthesizing a modulation output of the modulator and the second input signal. A second signal synthesis circuit (6) and an output signal of the second signal synthesis circuit; , A signal receiving circuit (5) for converting the signal into an intermediate frequency signal, a first phase detector (14) for detecting the intermediate frequency signal based on a synchronization signal of the input second input signal, and the synchronization signal. A second phase detector (15) for detecting the intermediate frequency signal by a signal shifted by 90 °, and the detection outputs of the two phase detectors (14, 15) as inputs and the low frequency signal respectively. It is characterized by comprising two product detectors (7, 8) that perform product detection and output the control voltage.

Further, in the present invention, the modulator (12) can be an amplitude modulator.

Further, in the present invention, the signal receiving circuit (5) can include an automatic gain control means.

Further, the present invention can include means for invalidating the output of the amplitude / phase control circuit when the second input signal is below a predetermined level.

[Action]

The modulator (12) modulates an interference wave mixed into an output signal of the signal synthesis circuit (4) with a low-frequency signal having a lower frequency than the interference wave. A signal combining circuit (6) combines the modulated output of the modulator and the second input signal. The signal receiving circuit (5) receives the output signal of the second signal synthesizing circuit and converts it into an intermediate frequency signal. The first phase detector (14) detects the intermediate frequency signal by a synchronization signal synchronized with the input second input signal, and the second phase detector (15) shifts the synchronization signal by 90 °. The intermediate frequency signal is detected based on the received signal. Further, the two product detectors (7, 8) cut the DC components of the detection outputs of the two phase detectors, respectively, perform product detection using the low-frequency signal, and use the low-pass filter to perform the product detection. The DC component of the output is extracted and given to the amplitude and phase control circuit as a control voltage.

The automatic gain control means of the signal receiving circuit (5) performs automatic gain control so that the DC component output of the phase detector becomes constant, and obtains a stable compensation operation for the level fluctuation of the second input signal. Can be made.

Further, when the second input signal is lower than the predetermined level, the output of the amplitude and phase control circuit is invalidated assuming that the interference wave has disappeared, thereby preventing a harmful influence on the desired received wave due to thermal noise or the like.

As described above, two signal receiving circuits are not required, and the configuration is simple and adjustment can be easily performed.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an interference compensation apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram of the amplitude / phase control circuit of the interference compensation device of the present invention. In FIG. 1, an interference compensator includes an input terminal 1 as a first input terminal for inputting a first input signal mixed with an interference wave in addition to a desired reception wave, and a second input terminal mainly including the interference wave. And an input terminal 2 as a second input terminal for inputting an input signal of the input signal, and controlling the second input signal based on a control voltage to be input so that the amplitude and the phase of the interference wave of the first input signal are substantially the same as those of the first input signal. An amplitude / phase control circuit 3 that outputs a substantially inverted signal, and a signal synthesis circuit that synthesizes an output signal of the amplitude / phase control circuit 3 and the first input signal to output an interference wave compensation signal. The circuit includes a circuit 4 and an interference wave compensation output terminal 10 for outputting the interference wave compensation signal.

The feature of the present invention is that the signal synthesizing circuit 4
A modulator 12 and a low-frequency oscillator 11 as modulators for modulating the output signal of the above with a low-frequency signal having a frequency lower than that of the interference wave, and combining the modulation output of the modulator 12 and the second input signal. A signal synthesis circuit 6 as a second signal synthesis circuit
A signal receiving circuit 5 which receives the output signal of the signal synthesizing circuit 6 as an input and converts the signal into an intermediate frequency signal; As the first phase detector for detecting the frequency signal, the phase detector 14 and the synchronization signal
A phase detector 15 as a second phase detector for detecting the intermediate frequency signal based on the phase-shifted signal;
A voltage-controlled oscillator 13 that inputs the detection output of 15 through a low-pass filter 27 and outputs the synchronization signal, and two phase detectors 1
The detection outputs of 4 and 15 are input through the high-pass filters 21 and 22, respectively, and multiply-detected by the low-frequency signal, and the control voltage is passed through the low-pass filters 23 and 24 and the DC integration circuits 25 and 26. And two multiplying detectors 7 and 8 that output as

 The modulator 12 is an amplitude modulator.

Further, the signal receiving circuit 5 includes automatic gain control means.

Further, a switch 16 connected to the output of the phase detector 14 is provided as means for invalidating the output of the amplitude / phase control circuit 3 when the second input signal is below a predetermined level.

FIG. 3 is a block diagram of the amplitude / phase control circuit of the interference compensator. In FIG. 3, 31 is an input terminal, 32 is a signal branch circuit, 33a to 33d are fixed phase shifters, 34a to 34d are PIN diode attenuators, 35 is a signal synthesizer, 36a and 36b are control signal input terminals and 37. Is an output terminal. The configuration and operation of FIG. 3 are described in detail in Japanese Patent Publication No. 62-16580.

The operation of the interference compensation device having such a configuration will be described. In FIG. 1, the interference wave input to the input terminal 2 is
Amplitude / Phase control circuit 3 and signal receiving circuit 5
Is input to The two-branched signal can be expressed as follows in a complex representation.

^{_{I A = i A e jΩt i}} A: amplitude interfering wave to the input terminal 2 Omega: against the interference wave angular frequency amplitude-phase control circuit 3 controls the voltage v _1, v _2, the output signal as follows Control and output.

_{I V = -K V (v 1} + jv 2) I A = -K V Vi A e j (Ωt + φ) -K V: the control sensitivity ^Ve jφ = v ₁ + jv ₂ amplitude phase control circuit 3 of the amplitude phase control circuit The output signal is combined with the signal from the input terminal 1 by the signal combining circuit 4. Interference signal from the input terminal 1 at this time is represented by the following ^{_{formula, I M = i M e j}} (Ωt + α) I M: amplitude of the interference wave to the input terminal 1 alpha: interference applied to the input terminal 1 The phase difference between the wave and the interference wave input to the input terminal 2 is as follows.

^{_{I R = i M e j (}} Ωt + α) -K v Vi A e j (Ωt + φ) = re j (Ωt + θ) _{^{However, re jθ = i M e jα}} -K V Vi A e jφ low frequency signal oscillator to the synthesized signal Modulator 12 with 11 outputs
In the above, when the amplitude modulation of "on"-"off" is performed, the amplitude can be represented by the following expression in a real number display.

ω: Modulated signal angular frequency When this is combined with the input signal of the input terminal 2 in the signal combining circuit 6, the following equation is obtained.

Next, the phase detector 14 detects the output AsinΩt of the voltage controlled oscillator 13.
When detected at, Taken out the DC component of the low-pass filter of this S _D1, applying an automatic gain control (AGC) as the DC component output becomes constant. That is, the DC voltage taken out by the low-pass filter is i _A A / 2 where i _A ≫r. Based on this, the amplification gain by the AGC is K / (i _A A / 2) K: constant, S _D1 Is given by

When the DC component of this equation is cut by a high-pass filter 21 such as a capacitor, and further multiplied and detected by a modulation signal, that is, an output signal of the low-frequency signal oscillator 11, the following equation is obtained. However, high-frequency components (components including 2Ω) are omitted.

The DC component of the detection output is obtained by the low-pass filter 23 and the DC integration circuit 25. That is, the output control voltage E ₁ of the product detector 7 is E ₁ = (2 / π ² ) (r / i _A ) cos θ. S is a signal obtained by shifting the output of the voltage controlled oscillator 13 by 90 °. The following equation is obtained by detection. Further, the following equation is obtained as a DC component obtained by multiplying and detecting the modulated signal. That is, the output control voltage of the product detector 8 is: E ₂ = (2 / π ² ) (r / i _A ) sin θ The two control voltages ₁ and E ₂ are amplified with an appropriate gain G, and the above control is performed. When the control is added to the voltage v _1, v _2, the output signal of the signal combining circuit 4 is given by the following ^{_{formula, I R = i a e j}} (Ωt + α) -K V Vi a e j (Ωt + φ) -K V (2KG / π ² ) re ^{j (Ωt + θ)} = (1-2K _V KG / π ² ) re ^{j (Ω t + θ) If the} control loop gain 2K _V KG / π ² is properly set, I _R eventually becomes “0”. The interference wave is suppressed, and a signal of only the desired wave is obtained from the interference wave compensation output terminal 10.

If the phase modulation of “0” − “π” is performed, the modulation signal is Thus, interference compensation can be performed in a similar process.
Interference wave compensation can be performed not by a modulated wave including harmonics but by a sine wave like “on”-“off” or “0”-“π” modulation.

Further, the method of synchronizing the voltage controlled oscillator 13 with the input signal can be realized by a phase locked loop for controlling the DC component of S _D2 ′ to be “0” or another carrier recovery circuit. However, in the case of "on"-"off" modulation in the phase locked loop, a synchronization error occurs when the interference compensation error is large, but the synchronization error can be ignored when the compensation operation proceeds to some extent.

The above description is for the case where AGC is performed, but it is possible to compensate for interference waves without performing AGC. However, the compensation operation becomes unstable because the loop gain fluctuates with respect to the level fluctuation of the input interference wave. Therefore, a stable compensation operation can be obtained by applying AGC.

Further, when transmission of a signal causing interference is stopped or the like, the interference compensator operates against thermal noise or the like, which may have a harmful effect on a desired wave. For this,
It is better to perform interference compensation only when an interference wave exists. That is, it is necessary to detect the interference wave level of the input signal of the input terminal 2 and to prevent the input signal of the input terminal 2 from being combined with the input signal of the input terminal 1 when no interference wave is detected. Specifically, the control voltage of the AGC is monitored, and when a voltage corresponding to a specified level equal to or higher than the noise level is detected, a switch 16 provided in the output signal of the amplitude / phase control circuit 3 is controlled to be turned on. There are various ways to do this.

〔The invention's effect〕

As described above, the present invention has an excellent effect that two signal receiving circuits are not required, the configuration is simple, and the adjustment is easy.

[Brief description of the drawings]

FIG. 1 is a block diagram of an interference compensation apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a conventional interference compensator. FIG. 3 is a block diagram of an amplitude / phase control circuit of the interference compensator. 1, 2,... Input terminals, 3,.
…… Signal synthesis circuit, 5, 5A, 5B …… Signal reception circuit, 7,
8 ... product detector, 9, 17 ... 90 degree phase shifter, 10 ... interference compensation output terminal, 11 ... low frequency signal oscillator, 12 ... modulator, 13 ... voltage controlled oscillator, 14, 15 …… Phase detector, 16
…… Switch, 21, 22 …… High-pass filter (HPF), 23, 2
4, 27 …… Low filter (LPF), 25, 26 …… DC integration circuit,
31 ... Input terminal, 32 ... Signal branch circuit, 33a-33d ... Fixed phase shifter, 34a-34d ... PIN diode attenuator, 35 ...
Signal combiner, 36a, 36b ... Control signal input terminal, 37 ... Output terminal.

Claims (4)

(57) [Claims] 1. A first input terminal (1) for inputting a first input signal mixed with an interference wave in addition to a desired reception wave, and a second input signal mainly containing the interference wave. A second input terminal (2) for controlling the second input signal based on the input control voltage and outputting a signal having substantially the same amplitude as the interference wave of the first input signal and having a substantially inverted phase; Interference comprising: an amplitude / phase control circuit (3); and a first signal synthesis circuit (4) that synthesizes an output signal of the amplitude / phase control circuit and the first input signal and outputs an interference wave compensation signal. In the compensator, a modulator (12) for modulating an output signal of the signal combining circuit with a low-frequency signal having a frequency lower than that of the interference wave, and a modulation output of the modulator and the second input signal. A second signal synthesizing circuit (6) to be synthesized, and an output of the second signal synthesizing circuit A signal receiving circuit (5) for receiving a signal and converting the signal into an intermediate frequency signal; a first phase detector (14) for detecting the intermediate frequency signal based on a synchronous signal of the input second input signal; and the synchronous signal A second phase detector (1) that detects the intermediate frequency signal by a signal shifted by 90 °
5) and two product detectors (7, 8) which receive the detection outputs of the two phase detectors (14, 15) as input, respectively, perform product detection with the low frequency signal, and output as the control voltage. An interference compensator comprising: 2. An interference compensator according to claim 1, wherein said modulator is an amplitude modulator. 3. An interference compensator according to claim 1, wherein said signal receiving circuit includes an automatic gain control means. 4. An interference compensator according to claim 1, further comprising means for invalidating the output of said amplitude / phase control circuit when said second input signal is below a predetermined level.