JP2951703B2 - 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 input terminal for controlling the second input signal based on a control voltage to be input and outputting a signal whose amplitude is substantially the same as that of the interference wave of the first input signal and whose phase is substantially inverted; Interference compensation comprising a phase control circuit (3) and a first signal combining circuit (4) for combining an output signal of the amplitude / phase control circuit and the first input signal to output an interference wave compensation signal. In the apparatus, a first modulator (12) for modulating an output signal of the signal combining circuit with a low-frequency signal having a lower frequency than the interference wave, and a signal obtained by shifting the output signal by 90 ° in phase. A second modulator (1) that modulates the frequency signal with a signal shifted by 90 ° 3) and these two modulators (12,
13) Second signal synthesis circuit that synthesizes the modulation output of (16)
A signal receiving circuit (5) which receives an output of the second signal synthesizing circuit as an input and converts the signal into an intermediate frequency signal, an envelope detector (9) which detects the intermediate frequency signal by an envelope, and an envelope detector Two product detectors (7, 8), each of which receives the output of the detector as an input, performs product detection with the low-frequency signal and a signal obtained by shifting the phase of the low-frequency signal by 90 °, and outputs the resultant as the control voltage. And characterized in that:

The present invention also provides the first and second modulators (12,
13) can both be amplitude modulators.

Further, in the present invention, a third signal synthesizing circuit (6) for synthesizing an output of the second signal synthesizing circuit (16) and the second input signal is provided at an input of the signal receiving circuit (5). Can be done.

In the present invention, the signal receiving circuit may 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 first modulator (12) modulates the output signal of the first signal synthesizing circuit (4) with a low-frequency signal having a lower frequency than the interference wave, and the second modulator (13) modulates the output signal. The signal obtained by shifting the signal by 90 ° is modulated by the signal obtained by shifting the low frequency signal by 90 °. A second signal combining circuit (16) combines the modulated outputs of the first and second modulators. An interference wave modulated by a low-frequency signal is output to the combined output. Now, it is assumed that the switch (20) is in the "OFF" state. The signal receiving circuit (5) receives the output of the second combining circuit and converts it into an intermediate frequency signal. An envelope detector (9) performs envelope detection on the intermediate frequency signal. The multiplying detectors (7, 8) cut the DC component of the detection output of the envelope detector and perform multiplying detection with the low-frequency signal and a signal obtained by shifting the low-frequency signal by 90 °, respectively. The bandpass filter extracts the DC component of the product detection output and supplies it to the amplitude and phase control circuit as a control voltage.

Considering the case where the switch (20) is "ON", the third signal synthesizing circuit (6) synthesizes the output of the second signal synthesizing circuit (16) and the second input signal, and the signal receiving circuit Give to. An automatic gain control means can be provided in the signal receiving circuit so that a stable compensation operation can be obtained for the level fluctuation of the second input signal.

Further, when the second input signal is lower than the predetermined level, the output signal of the amplitude / phase control circuit is invalidated assuming that the interference wave has disappeared.

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 first modulator that modulates the output signal of the first signal with a low-frequency signal having a frequency lower than that of the interference wave, and
Modulator 1 as a second modulator that modulates the phase-shifted signal with this low-frequency signal shifted by 90 °
2, 13, 90 ° phase shifters 11, 15 and low-frequency signal oscillator 14
A signal synthesizing circuit 16 as a second signal synthesizing circuit for synthesizing the modulation outputs of the modulators 12 and 13; a signal receiving circuit 5 which receives the output of the signal synthesizing circuit 16 as an input and converts it into an intermediate frequency signal; An envelope detector 9 for envelope detection of a signal and an output of the envelope detector 9 are input through high-pass filters 21 and 22, respectively, and the phases of the low-frequency signal and the low-frequency signal are detected.
It is provided with two product detectors 7 and 8 that respectively perform product detection on the signals whose phases have been shifted by 90 ° and output the control voltages through low-pass filters 23 and 24 and DC integration circuits 25 and 26. It is in. The modulators 12 and 13 are both amplitude modulators here.

Further, a signal synthesizing circuit 6 is provided as an input of the signal receiving circuit 5 as a third signal synthesizing circuit for synthesizing the output of the signal synthesizing circuit 16 and the second input signal.

 The signal receiving circuit 5 includes an automatic gain control unit.

Further, a switch 18 connected to the output of the envelope detector 9 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.

Branch ^{_{I R = i M e j (}} Ωt + α) -K V Vi A e j (Ωt + φ) = re j (Ωt + θ) However, the _{^{re jθ = i M e jα -K}} V Vi A e jφ this combined signal into two systems When the phase of one of the two branched signals is shifted by 90 °, each signal can be expressed as follows.

Each of these signals has a low-frequency signal oscillator 14 with a phase difference of 90 °.
The output signal of the phase shifter 15 and the signal whose phase has been shifted by the 90 ° phase shifter 15 are “on” by the modulators 12 and 13, respectively.
When the amplitude modulation of “OFF” is performed, it can be expressed by the following equation.

ω: Modulated signal angular frequency The two signals subjected to the amplitude modulation are combined by the signal combining circuit 16 and the combined signal and the input signal of the input terminal 2 are combined by the signal combining circuit 6 to obtain the following equation.

When this composite signal is subjected to, for example, square detection by the envelope detector 9, the following equation is obtained.

Taken out DC component of the S ² in the low-pass filter, multiplying the automatic gain control (AGC) as the DC component output becomes constant.
Ie dc voltage taken out by the low-pass filter is, i _A ^2/2 However i _A >> R amplification gain by the AGC based on this However, if K = constant, S ² is given by the following equation.

This type of DC component is filtered by high-pass filters 21, 22 such as capacitors.
Cut by the modulated signal, ie the low frequency signal oscillator
The output signal of 14 and the signal whose phase has been shifted by the 90 ° phase shifter 15 are subjected to product detection in the product detectors 7 and 8,
The DC component of the detection output is obtained by low-pass filters 23 and 24 and DC integration circuits 25 and 26. That is, the product detectors 7, 8
Control voltages E ₁ and E ₂ output by the following equation.

E ₁ = (K ² r / π ² i _A ) cos θ E ₂ = (K ² r / π ² i _A ) sin θ where i _A ≫r These two output signals E ₁ and E ₂ are divided by an appropriate gain G. Amplify,
When the control is added to the control voltage v _1, v ₂ described above, the output signal of the signal combining circuit 4 is given by the following ^{_{formula, I R = i M e j}} (Ωt + α) -K V Vi A e j (Ωt + φ) -K ^{_{V (K 2 G / π 2}} ) re j (Ωt + θ) = {1- (k r K 2 G / π 2)} re j (Ωt + θ) control loop gain K _V K ² G / π ² appropriately setting them For example, I _R becomes “0”, the interference wave is finally 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 and Thus, interference wave compensation can be performed in a similar process.
Interference wave compensation can be performed not by a modulation wave including a high frequency but by a sine wave modulation such as “on”-“off” or “0”-“π” modulation.

In the above description, the case of the square detection by the envelope detector 9 has been described. However, as a method for obtaining the envelope, a signal AsinΩt (A: At) synchronized with the interference wave input to the input terminal 2 by a phase synchronization circuit or the like. Constant), and the same result can be obtained by detection with this. That is, if S is detected by AsinΩt, However, a term including a high-frequency component, that is, a frequency component of 2Ω is omitted. This DC component (However, if I apply AGC with i _A ≫r) Excluding this DC component, the product signals are subjected to product detection in the product detectors 7 and 8 using the modulated signal, that is, the output signal of the low-frequency signal oscillator 14 and the signal whose phase has been shifted by the 90 ° phase shifter 15. Get a minute.

_{E 1 = (K r / π} 2 i A) (1 + 1/9 + 1/25 + 1/49 + ... ‥) sinθ ≒ 0.125 (Kr / i A) sinθ E 2 = (Kr / π 2 i A) (1 + 1/9 + 1 / 25 + 1/49 +...)) Cos θ K0.125 (Kr / i _A ) cos θ As described above, a voltage proportional to (r / i _A ) cos θ and (r / i _A ) sin θ is obtained, and interference occurs. Can suppress waves.

Although AGC is performed in a high frequency band and an intermediate frequency band, it is also possible to use AGC in a low frequency band or a DC signal. For example, in the high frequency band, the intermediate frequency band
DC voltage E ₁ when not wearing the AGC becomes the following equation when the square-law detection.

_{E 1 = (i A r /} 2π 2) cosθ which based on the DC component i _A ^2/2 of the square-law detection output 2K / i
Amplify with a gain of _A ² (K is constant). As a result, the DC voltage
E ₁ is as follows, with similar results.

E ₁ = (Kr / π ² i _A ) cos θ The above description is for the case where AGC is performed, but the interference wave can be compensated 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 predetermined level equal to or higher than the noise level is detected, the switch 18 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 ... amplitude and phase control circuit, 4,
6, 16 ... signal synthesis circuit, 5, 5A, 5B ... signal reception circuit, 7, 8 ... product detector, 9 ... envelope detector, 10 ...
… Interference wave compensation output terminal, 11, 15, 17 …… 90 ° phase shifter, 1
2, 13… Modulator, 14… Low-frequency signal oscillator, 18, 20…
… Switch, 21, 22 …… High-pass filter (HPF), 23, 24…
… Low-pass filter (LPF), 25, 26 …… DC integration circuit, 31…
... Input terminals, 32 ... Signal branch circuits, 33a-33d ... Fixed phase shifters, 34a-34d ... PIN diode attenuators, 35 ... Signal combiners, 36a, 36b ... Control signal input terminals, 37 ... ... Output terminal.

Claims (5)

(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 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; 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 first modulator for modulating an output signal of the signal combining circuit with a low-frequency signal having a lower frequency than the interference wave (12)
And a second modulator (13) for modulating a signal obtained by shifting the output signal by 90 ° with a signal obtained by shifting the low-frequency signal by 90 °, and a modulation of the two modulators (12, 13). A second signal synthesizing circuit (16) for synthesizing an output, a signal receiving circuit (5) for receiving an output of the second signal synthesizing circuit as an input and converting the intermediate frequency signal into an intermediate frequency signal, and performing envelope detection on the intermediate frequency signal An envelope detector (9), and the outputs of the envelope detector are respectively input and the low frequency signal and a signal obtained by shifting the phase of the low frequency signal by 90 ° are respectively multiplied and detected to obtain the control voltage. An interference compensator comprising: two output product detectors (7, 8) for outputting. 2. An interference compensator according to claim 1, wherein said first and second modulators (12, 13) are both amplitude modulators. 3. A third signal synthesizing circuit (6) for synthesizing an output of the second signal synthesizing circuit (16) and the second input signal at an input of the signal receiving circuit (5). The interference compensator according to claim 1. 4. An interference compensator according to claim 3, wherein said signal receiving circuit includes an automatic gain control means. 5. An interference compensator according to claim 3, further comprising means for invalidating the output of said amplitude / phase control circuit when said second input signal is lower than a predetermined level.