JPH0490626A - Interference compensating device - Google Patents

Abstract

PURPOSE:To simplify construction without necessitating a dual signal reception circuit by suppressing an interference wave in radio communication and receiving the only signal to be desired. CONSTITUTION:A modulator 12 modulating the output signal of a first signal synthesis circuit 4 by a low frequency signal with low frequency compared with the interference wave, a second signal synthesis circuit 6 synthesizing the modulation output of the modulator 12 and the second input signal, a signal reception circuit 5 taking the output signal of this circuit 6 as input to be converted to an intermediate frequency signal, a first phase detector 14 detecting the intermediate frequency signal by the synchronizing signal of a second input signal to be inputted, a second phase detector 15 detecting the intermediate frequency signal with a phase-transferred signal, two product detectors 7 and 8 taking the detection output of the two phase detectors 14 and 15 as input respectively and outputting them as control voltage after product-detection by a low frequency signal, are provided. Thus, the construction is simplified without necessitating the dual signal reception circuit.

Description

[Detailed description of the invention] [Industrial application field] INDUSTRIAL APPLICATION This invention is utilized for the interference compensation apparatus of wireless communication.

In particular, the present invention relates to a device that suppresses interference waves and receives a desired signal.

[Conventional technology]

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

Conventionally, an interference compensator has had a configuration as shown in FIG. In FIG. 2, 1.2 is an input terminal, 3 is an amplitude phase control circuit, 4 is a signal synthesis circuit, and 5A.

Reference numeral 5B indicates a signal receiving circuit composed of an amplifier, a frequency converter, a bandpass filter, etc., 7.8 a product detector, 10 an interference wave compensation output terminal, and 17 a 90° phase shifter.

Signals for normal communication are input to input terminal 1, but
Interference waves are also mixed in. Interference waves are mainly input to the input terminal 2. The interference wave input to input terminal 2 is branched into two systems,
One signal has its amplitude and phase controlled by an amplitude and phase control circuit 3, and is combined with the signal from the input terminal 1 by a signal synthesis circuit 4.

This composite signal and the other signal at input terminal 2 are frequency-converted and amplified by signal receiving circuits 5A and 5B, respectively, and then branched into two and detected by product detector 7.8. At this time, one of the four signals input to the product detector 7.8 is shifted in phase by 90" by the 90° phase shifter 17. The output signal of the product detector 7.8 is input to the input terminal 1. The amplitude and phase control circuit 3 is controlled so that the interference wave input from the input terminal 2 and the interference wave input from the input terminal 2 have the same amplitude and reverse phase.

As described above, a signal containing no interference waves can be obtained in the output of the interference wave compensation output terminal 10.

[Problem to be solved by the invention]

However, such conventional interference compensation devices require two systems of signal receiving circuits, and in order to accurately suppress interference waves, it is necessary to match the phase and amplitude fluctuation characteristics of both signal receiving circuits. Therefore, it has the disadvantage that it has a large number of components, making it difficult to adjust the fluctuations in its amplitude and phase characteristics.

The present invention solves the above-mentioned drawbacks, and aims to provide an interference compensating device that does not require two signal receiving circuits, has a simple configuration, and is easy to adjust.

[Means to solve the problem]

The present invention comprises a first input terminal (1) to which a first input signal mixed with interference waves in addition to the desired received wave is input, and a second input terminal (1) to which a second input signal having the interference wave as a main component is input. a second input terminal (2>) and an amplitude phase that controls the second input signal based on the input control voltage and outputs a signal whose amplitude is almost equal to that of the interference wave of the first input signal and whose phase is almost reversed. An interference compensation device comprising a control circuit (3) and a first signal synthesis circuit (4) that synthesizes the output signal of the amplitude phase control circuit and the first input signal to output an interference wave compensation signal. a modulator (1) that modulates the output signal of the signal synthesis circuit with a low frequency signal having a lower frequency than the interference wave;
2), a second signal synthesis circuit (6) that synthesizes the modulated output of this modulator and the second input signal, and the output signal of this second signal synthesis circuit is input and converted into an intermediate frequency signal. a first phase detector (14) that detects the intermediate frequency signal using a synchronization signal of the second input signal, and a signal obtained by shifting the phase of the synchronization signal by 90 degrees. a second phase detector (15) that detects the intermediate frequency signal; and a second phase detector (15) that detects the intermediate frequency signal;
The present invention is characterized in that it includes two product detectors (7, 8) each receiving the detection output of 5), performing product detection using the low frequency signal, and outputting the product as the control voltage.

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

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

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

[Effect]

The modulator (12) modulates the interference wave mixed in the output signal of the signal synthesis circuit (4) with a low frequency signal whose frequency is lower than that of the interference wave. A signal combining circuit (6) combines the modulated output of this modulator and the second input signal. The signal receiving circuit (5) receives the output signal of the second signal synthesis circuit and converts it into an intermediate frequency signal. The first phase detector (14) detects the intermediate frequency signal using a synchronization signal synchronized with the input second input signal, and the second phase detector (15) shifts the phase of the synchronization signal by 90°. The intermediate frequency signal is detected by the detected signal. Furthermore, two product detectors (7, 8)
Cuts the DC components of the detection outputs of the two phase detectors, performs product detection using the low frequency signal, extracts the DC component of the product detection output using a low-pass filter, and uses it as a control voltage in the amplitude phase control circuit. give to

Further, 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 is constant, so that a stable compensation operation can be achieved with respect to level fluctuations of the second input signal. You can make it possible to

Furthermore, when the second input signal is below a predetermined level, it is assumed that there is no interference wave and the output of the amplitude phase control circuit is invalidated to prevent harmful effects such as thermal noise on the desired received wave.

As a result of the above, two systems of signal receiving circuits are not required, and the configuration is simple and adjustment can be made easily.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram of an interference compensation device according to an embodiment of the present invention. FIG. 3 is a block diagram of the amplitude and phase control circuit of the interference compensator of the present invention.

In FIG. 1, the interference compensator has an input terminal 1 as a first input terminal to which a first input signal mixed with interference waves in addition to the desired received wave is input, and a second input terminal whose main component is the interference wave. Input terminal 2 serves as the second input terminal for inputting the input signal of
and an amplitude phase control circuit 3 which controls the second input signal based on the input control voltage and outputs a signal having substantially the same amplitude and substantially inverted phase as the interference wave of the first input signal.
and a signal synthesis circuit 4 as a first signal synthesis circuit which synthesizes the output signal of the amplitude phase control circuit 3 and the first input signal and outputs an interference wave compensation signal, and outputs this interference wave compensation signal. and an interference wave compensation output terminal 10.

Here, the present invention is characterized in that a modulator 12 and a low frequency oscillator 11 are used as a modulator for modulating the output signal of the signal synthesis circuit 4 with a low frequency signal whose frequency is lower than that of the interference wave. a signal synthesizing circuit 6 as a second signal synthesizing circuit that synthesizes the modulated output of 12 and the second input signal; a signal receiving circuit 5 that receives the output signal of the signal synthesizing circuit 6 and converts it into an intermediate frequency signal; A phase detector 14 as a first phase detector detects the intermediate frequency signal using a synchronizing signal synchronized with the second input signal to be input, and a synchronizing signal synchronized with the intermediate frequency signal. A phase detector 15 serves as a second phase detector that detects the intermediate frequency signal using the shifted signal, and a voltage that inputs the detection output of the phase detector 15 via a low-pass filter 27 and outputs the synchronization signal. The detected outputs of the controlled oscillator 13 and the two phase detectors 14 and 15 are inputted through high-pass filters 21 and 22, respectively, and subjected to product detection using the above-mentioned low frequency signals. Two product detectors 7.8 are provided which output the control voltages via circuits 25 and 26.

Moreover, 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 and phase control circuit 3 when the second input signal is below a predetermined level.

FIG. 3 is a block diagram of the amplitude and 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, and 34a is a signal branch circuit.
34d is a PIN diode attenuator, 35 is a signal combiner, 36a and 36b are control signal input terminals, and 37 is an output terminal. The structure and operation of FIG. 3 are explained in detail in Japanese Patent Publication No. 16580/1983.

The operation of the interference compensation device having such a configuration will be explained. In Fig. 1, the interference wave input to input terminal 2 is 2
The signal is branched and input to the amplitude phase control circuit 3 and the signal receiving circuit 5. This two-branched signal can be expressed in complex form as follows.

IA=i, ej or lA Amplitude Ω of the interference wave input to the two input terminals 2: In the interference wave angular frequency amplitude phase control circuit 3, for the control voltages v1 and v2,
The output signal is controlled and output as follows.

Iv = Kv (V+ + J V2) I
A-KvViA ej(ΩL+〆) Kv: Control sensitivity of the amplitude phase control circuit V ejf'= V, + j V3 The output signal of this amplitude phase control circuit 3 is transmitted to the signal synthesis circuit 4
It is combined with the signal from input terminal 1.

At this time, the interference wave signal from input terminal 1 is expressed by the following formula, ■ = 1we io Amplitude α of interference wave input to two input terminals 1: Interference wave input to input terminal 1 and input to input terminal 2 The phase difference composite signal with the interference wave is given by the following equation.

1, = i, ej(fLt+men -K V V
I A eJ (Q(+Me1:=: r e J (O
L lines θ] However, if re"=iXe"-, ViAe'1 This composite signal is subjected to "on"-"off" amplitude modulation in the modulator 12 using the output of the low frequency signal oscillator 11, and then it is expressed as a real number. It can be expressed as the following formula.

I+'=rsin(Ωt+θ) (1/2+ (2/π) cos (2n-1) ωt) ω: Modulation signal angular frequency When this is combined with the input signal of input terminal 2 in signal synthesis circuit 6, the following equation is obtained. .

5=iA sinΩt+rsin(Ωt+θ)(1/2
+ (2/π) cos (2n-1) ωt) Next, when the output As1nΩt of the voltage controlled oscillator 13 is detected by the phase detector 14, Sn+= (IA A/2)(1cos2Ωt)+(r
A/4) (cosθ - cos (2Ω to 10θ)) ÷ (rA/π) (cosθ - cos (2Ωt+θ)) cos (2n-1) ωt) The DC component of this 5ell is extracted with a low-pass filter, Automatic gain control (AGC) is applied so that this DC output is constant. In other words, the DC voltage taken out by the low-pass filter is IAA/, where iA>r, and based on this, the amplification gain by AGC is K/
(IA A/2) If K is constant, SDI is expressed as follows.

Sa+ =K(I CO52Ωt)+ (Kr/
iA) (cosθ cos(2Ωt+θ)) ((1-2)+ (2/π) cos (2n-1)act) The DC component of this formula is cut by a high-pass filter 21 such as a capacitor, and the modulated signal, That is, the low frequency signal oscillator 11
Further product detection is performed on the output signal of , and the following equation is obtained. However, harmonic components (components including 2Ω) are omitted.

e+ = (2Kr/πi,)cosθcos (2
n-1) (lJt) (1/2+ (2/π) cos (2n-1) act) A DC component of this detection output is obtained by a low-pass filter 23 and a DC integration circuit 25. That is, the output control voltage E1 of the multiplicative product detector 7 is E, = (2/π2) (r/1A) cosθ.If S is detected by a signal obtained by shifting the output of the voltage controlled oscillator 13 by 90°, then the following equation can be obtained. The formula becomes, SD2' = Ks i n
2Ω to 10 (Kr/1A) (sinθ+5in(2Ωt+
θ)) (1/2+ (2/π) 1, =t Ae J In t ” m ]
KvV I AeJ [”t”〆)-Kv (2KG
/π2)roj[Ωt+σ)=(1-2Kv KG
/rr2) r eJC”θ) Control loop gain 2KvKG
If /π2 is appropriately set, Ii+ will eventually become "0", the interference wave will be suppressed, and a signal containing only the desired wave will be obtained from the interference wave compensation output terminal 10.

Also, if we perform phase modulation of ``rQJ rπ'',
The modulated signal is cos (2n-1) ωt) Furthermore, the following equation is obtained as a DC component obtained by product detection using the modulated signal. That is, the output control voltage of the multiplicative detector 8 is E2 = (2/π2) (r/1A) sin θ These two control voltages 1 and E2 are amplified with an appropriate gain G, and the above control voltage v1, When controlled by adding it to v2, the output signal of the signal synthesis circuit 4 becomes the following formula, cos (2n-1)
cc+t, and interference compensation is possible through a similar process. "
Interference wave compensation is also possible using a sine wave rather than a modulated wave including harmonics such as "on"-"off" or rQJ rπ" modulation.

Further, the method of synchronizing the voltage controlled oscillator 13 with the input signal can be realized by a phase-locked loop or other carrier wave recovery circuit that controls the DC component of S[12' to become "O". However, in a phase-locked loop, “on” −
In the case of "off" modulation, a synchronization error occurs when the interference compensation error is large, but once the compensation operation has progressed to a certain extent, the synchronization error can be ignored.

The above explanation is about the case where AGC is performed.
It is possible to compensate for interference waves without performing C. but,
Since the loop gain fluctuates in response to level fluctuations of the input interference wave, the compensation operation becomes unstable. For this reason, a more stable compensation operation can be obtained by applying AGC.

Furthermore, if the transmission of an interfering signal is stopped, the interference compensator operates against thermal noise, etc., and may have a detrimental effect on the desired wave. In addition, it is better to perform interference compensation only when interference waves exist. In other words, the interference wave level of the input signal of input terminal 2 is detected, and when no interference wave is detected, the level of the interference wave of the input signal of input terminal 2 is detected.
It is necessary to prevent the input signal of input terminal 2 from being combined with the input signal of input terminal 2. Specifically, the control voltage of the AGC is monitored, and when a voltage corresponding to a specified level higher than the noise level is detected, the switch 16 provided for the output signal of the amplitude phase control circuit 3 is controlled to be turned on. There are ways to do this.

[Effects of the Invention] As described above, the present invention has excellent effects in that two signal receiving circuits are not required, and the configuration is simple and adjustment is easy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an interference compensation device according to an embodiment of the present invention. FIG. 2 is a block diagram of a conventional interference compensation device. FIG. 3 is a block diagram of the amplitude and phase control circuit of the interference compensator. 1.2... Input terminal, 3... Amplitude phase control circuit, 4
．． 6... Signal synthesis circuit, 5.5A, 5B... Signal receiving circuit, 7.8... Product detector, 9.17...90
° 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
．． 24.27...Low filter (LPF), 25.26.
...DC integration circuit, 31...Input terminal, 32...Signal branch circuit, 33a to 33d...Fixed phase shifter, 34a
~34d...PIN diode attenuator, 35...signal combiner, 36a, 36b...control signal input terminal, 3
7...Output terminal. Patent applicant: Nippon Telegraph and Telephone Corporation Representative Patent attorney: Naotaka Ide

Claims (1)

[Claims] 1. A first input terminal (1) into which a first input signal mixed with an interference wave in addition to the desired received wave is input, and a second input signal whose main component is the interference wave. The second input terminal (2
), and an amplitude phase control circuit (3) that controls the second input signal based on the input control voltage and outputs a signal having substantially the same amplitude and substantially inverted phase as the interference wave of the first input signal. and a first signal combining circuit (4) that combines the output signal of the amplitude phase control circuit and the first input signal to output an interference wave compensation signal, the signal combining circuit comprising: a modulator (12) that modulates the output signal of the circuit with a low frequency signal having a lower frequency than the interference wave;
a second signal synthesis circuit (6) that synthesizes the modulated output of this modulator and the second input signal; and a signal reception circuit that receives the output signal of this second signal synthesis circuit and converts it into an intermediate frequency signal. (5), a first phase detector (14) that detects the intermediate frequency signal using the synchronization signal of the second input signal; a second phase detector (15) that detects the voltage, and a second phase detector (15) that receives the detection outputs of the two phase detectors (14, 15) as inputs, performs product detection using the low frequency signal, and outputs the control voltage as the control voltage. An interference compensation device characterized by comprising two multiplicative detectors (7, 8). 2. The interference compensation device according to claim 1, wherein the modulator (12) is an amplitude modulator. 3. The interference compensation device according to claim 1, wherein the signal receiving circuit (5) includes automatic gain control means. 4. The interference compensation device according to claim 1, further comprising means for invalidating the output of the amplitude and phase control circuit when the second input signal is below a predetermined level.