JPH0525410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an interference wave removal device, and more particularly to an interference wave removal device used in a microwave digital transmission system in which FM interference waves from other routes exist.

[Conventional technology]

If a microwave digital transmission system receives interference from a microwave FM transmission system in the same frequency band, it is necessary to add an interference wave removal device to the microwave digital transmission system to remove the influence of the FM interference waves.

One of the conventional examples of such an interference wave removal device is the Japanese Patent Application Laid-open No.
Some of these are described in Publication No. 58-131853.
In this conventional example, an interference wave signal is extracted from an input signal containing an interference wave using a narrowband wave circuit, and the amplitude and phase of the extracted interference wave signal are controlled by a control signal to create a cancellation signal. The canceling signal is subtracted to obtain an output signal from which the interference wave has been removed. The control signal is obtained by orthogonally multiplying the extracted interference wave signal and the output signal. In other words, if there is an amplitude error or a phase error in the cancellation signal, there will be a residual interference wave in the output signal, so an amplitude error signal will be generated in one of the two outputs of orthogonal multiplication, and a phase error signal will be generated in the other, and these error signals will be It becomes a control signal.

A phase-locked loop that is phase-locked to an interference wave is known as a means for realizing a narrowband wave circuit. The phase-locked loop operates as a good narrowband wave circuit because the band width of the wave circuit can be determined by the low frequency filter in the loop.

However, such narrowband wave circuits generate an output whose phase and frequency are unrelated to the interfering wave if the loop is out of phase lock, and this output does not create a canceling signal that cancels out the interfering wave in the input signal. This becomes a new interference wave and is injected into the input signal.

[Problem that the invention seeks to solve]

As explained above, conventional interference wave removal devices are
When the operation of the narrowband wave circuit is not normal, interference waves are injected into the input signal, and instead of suppressing the interference waves,
The drawback is that it actually degrades the quality of the line.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an interference wave removal device that solves the above-mentioned drawbacks and does not deteriorate line quality even when the operation of a narrowband wave circuit is not normal.

[Means for solving problems]

The interference wave removal device of the present invention includes narrowband wave means for extracting an interference wave signal from an input signal including an interference wave, and an amplitude phase control means for controlling the amplitude and phase of the interference wave signal by a control signal. subtraction means for subtracting the output of the amplitude and phase control means from the input signal; and control signal generation for obtaining the control signal by orthogonally multiplying either the input signal or the interference wave signal and the output of the subtraction means. The interference wave removing device comprises means for inhibiting the output of the amplitude and phase control means when the operation of the narrowband wave means is not normal.

〔Example〕

The present invention will be described in detail below with reference to the drawings showing embodiments.

FIG. 1 is a block diagram showing an embodiment of an interference wave removal device of the present invention.

The embodiment shown in FIG. 1 includes an interference wave extraction circuit 1 that inputs an input signal 101 containing interference waves and outputs extracted interference signals 102 and 103, and an interference wave extraction circuit 1 that is connected to the interference wave extraction circuit 1 and outputs an out-of-synchronization signal 104. An out-of-synchronization detection circuit 2, an amplitude phase control circuit 3 that inputs the extracted interference signal 102, amplitude error signal 107, and phase error signal 108 and outputs a cancellation signal 105, and outputs a cancellation signal 10 when the out-of-synchronization signal 104 is not input.
5 is passed through as is, and when input, the cancellation signal 1
05, a subtracter 5 that subtracts the output of the attenuator 4 from the input signal 101 and outputs the output signal 106, and receives the extracted interference signal 103 and the output signal 106 and outputs the amplitude error signal 107 and the phase error. Control signal generation circuit 6 that outputs signal 108
It is configured with the following.

The interference wave extraction circuit 1 includes a bandpass filter 11 that receives an input signal 101 and suppresses components other than interference waves;
A phase comparator 12 that compares the phases of the outputs of the bandpass converters 11 and 15, a low-pass converter 13 that limits the band of the output of the phase comparator 12, and a voltage control whose frequency is controlled by the output of the low-band converter 13. an oscillator 14;
It is configured to include a band wave generator 15 that provides a delay equivalent to the delay of the band wave generator 11 to the output of the voltage controlled oscillator 14. The outputs of the voltage controlled oscillator 14 and band wave generator 15 are branched to extract an interference signal 10.
It becomes 2,103.

The out-of-synchronization detection circuit 2 outputs an out-of-synchronization signal 104 when the sweep oscillator 21 oscillates with a sweep oscillator 21 connected to a connection line connecting the phase comparator 12 and the low-frequency amplifier 13 of the interference wave extraction circuit 1. The level detector 22 is configured to include a level detector 22 that

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, the operation of the interference wave extraction circuit 1 will be explained.

The bandpass filter 11 improves the C/N of the interference wave input to the phase comparator 12. Phase comparator 12・
The frequency of the extracted interference signals 102 and 103 matches the frequency of the interference wave output from the bandpass generator 11 due to the action of the phase locked loop consisting of the low frequency wave generator 13, the voltage controlled oscillator 14, and the bandpass wave generator 15. The bandwidth of the extracted interference signals 102 and 103 is determined by the low frequency filter 13. The phase of the extracted interference signal 103 matches the phase of the output of the band wave generator 11, and when the frequency of the interference wave changes, the phase of the output of the band wave generator 11 changes.
Since the passing phase of the interference signal 103 changes, the phase of the extracted interference signal 103 also changes by the amount of this phase change. On the other hand, since the passing phases of the bandpass filters 11 and 15 cancel each other out, even if the frequency of the interference wave changes, the phase of the extracted interference signal 102 does not change. Note that since the band waver 15 has the function of canceling the delay characteristics of the band wave waver 11, the band wave waver 15
Instead, a delay circuit whose delay characteristics are equivalent to that of the bandpass converter 11 may be used.

Next, the operation of the out-of-sync detection circuit 2 will be explained.

The phase locked loop of the interference wave extraction circuit 1 is connected to the sweep oscillator 21 so as to become part of the load impedance of the sweep oscillator 21. The impedance from the sweep oscillator 21 to the phase-locked loop is:
When the phase-locked loop is in lock, it has low impedance, and when it is out of lock, it has high impedance. The sweep oscillator 21 is adjusted so that it oscillates when the impedance considering the phase-locked loop becomes high impedance, and does not oscillate when the impedance becomes low. With this adjustment, the sweep oscillator 21 will not oscillate if the interference wave extraction circuit 1 is operating normally and the phase-locked loop is in a synchronized state. Therefore, the level detector 22 that detects the output level of the sweep oscillator 21 The out-of-synchronization signal 104 is not output. When the operation of the interference wave extraction circuit 1 becomes abnormal and the phase-locked loop becomes out of synchronization, the sweep oscillator 21 oscillates, and the level detector 22
outputs an out-of-sync signal 104. The detailed configuration of such an out-of-synchronization detection circuit is
This is disclosed in Publication No. 34619, so please refer to this publication if necessary.

The interference wave extraction circuit 1 normally extracts interference signals 102 and 10 in phase synchronization with the interference wave in the input signal 101.
3, the amplitude and phase control circuit 3 controls the amplitude and phase of the extracted interference signal 102 to create a cancellation signal 105, in which case the out-of-synchronization signal 10
4 is not input, the attenuator 4 has a cancellation signal of 10.
Output 5 as is. Subtractor 5 receives input signal 1
By combining 01 and the cancellation signal 105 with opposite phases, the interference wave included in the input signal 101 is suppressed,
An output signal 106 with suppressed interference waves is output.
The control signal generation circuit 6 extracts the interference wave remaining in the output signal 106 using a bandpass filter, and orthogonally multiplies the extracted residual interference wave and the extracted interference signal 103 to generate an amplitude error signal 107 and a phase error signal 108. Occur. The amplitude error signal 107 and the phase error signal 108 are fed back to the amplitude and phase control circuit 3. The interference wave suppression operation using a loop consisting of the amplitude phase control circuit 3, attenuator 4, subtractor 5, and control signal generation circuit 6 is described in the already mentioned Japanese Patent Application Laid-Open No.
It is explained in detail in Publication No. 131853, so please refer to this publication if necessary. In the embodiment shown in FIG. 1, even if the frequency of the interference wave changes, the phase of the extracted interference signal 102 does not change, and the bandpass filter that extracts the residual interference wave from the output signal 106 performs orthogonal multiplication. Even if the phase of one input varies, this phase variation is canceled by the phase variation of the extracted interference signal 103, which is the other input, and the phase relationship of orthogonal multiplication is maintained correctly, so the frequency of the interference wave changes. It has the characteristic that the degree of suppression of interference waves does not deteriorate even if the interference waves fluctuate.

Now, when the phase-locked loop of the interference wave extraction circuit 1 becomes out of synchronization, the extracted interference signal 102
becomes a signal that is unrelated to the interference wave included in the input signal 101 in both frequency and phase, and the amplitude and phase control circuit 3 can no longer generate a normal cancellation signal 105, but instead outputs an interference wave. However, in this case, an out-of-synchronization signal 104 is generated, and the attenuator 4 provides large attenuation to the output of the amplitude and phase control circuit 3 to prevent the interference wave from inputting to the subtracter 5. In this way, the embodiment shown in FIG. 1 prevents interference waves from being injected into the input signal 101 when the operation of the interference wave extraction circuit 1 is not normal.

The attenuator 4 only needs to have a function of prohibiting the output of the amplitude phase control circuit 3 from being input to the subtracter 5 when the out-of-synchronization signal 104 is input. 104 may be used, or the amplitude control mechanism included in the amplitude and phase control circuit 3 may be directly controlled by the out-of-synchronization signal 104.

It is also possible to use the input signal 101 itself instead of the output of the interference wave extraction circuit 1 as one input of the control signal generation circuit 6.

Regarding the type of interference waves, the present invention is applicable not only to FM interference waves but also to all interference waves in which carrier components are dominant.

〔Effect of the invention〕

As explained in detail above, the interference wave removal device of the present invention does not inject interference waves into the input signal when the operation of the narrowband wave circuit is not normal. This also has the effect of not degrading the quality of the line.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an interference wave removal device of the present invention. DESCRIPTION OF SYMBOLS 1... Interference wave extraction circuit, 2... Out-of-synchronization detection circuit, 3... Amplitude phase control circuit, 4... Attenuator, 5
...Subtractor, 6...Control signal generation circuit.

Claims (1)

[Scope of Claims] 1. Narrowband wave means for extracting an interference wave signal from an input signal including an interference wave; amplitude and phase control means for controlling the amplitude and phase of the interference wave signal by a control signal; subtracting means for subtracting the output of the amplitude phase control means from the signal; and control signal generating means for obtaining the control signal by orthogonally multiplying either the input signal or the interference wave signal and the output of the subtracting means. An interference wave removal device comprising: means for inhibiting the output of the amplitude phase control means when the operation of the narrowband wave means is not normal.