JPH0525411B2 - - 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. In other words, a bandpass filter extracts the interference wave component from the input signal, a phase comparator compares the phase of this interference wave component with the output of the voltage controlled oscillator, and the phase difference output controls the frequency of the voltage controlled oscillator to eliminate interference. wave signal is obtained. The bandwidth of the narrowband wave circuit is determined by the bandwidth of the low-frequency wave generator that band-limits the phase difference output. The bandwidth of the bandpass filter must be narrow enough to improve the input C/N of the phase comparator and allow the phase-locked loop to operate stably.

Now, in the narrow band wave circuit using the above means, it is necessary to have a narrow band wave generator for extracting interference wave components, and when the frequency of the constant wave changes, the passing phase of this band wave wave generator changes greatly, and this phase change As a result, the phase of the interference wave signal output from the voltage controlled oscillator also varies greatly, making it difficult to control the phase ratio of the interference wave signal to create a cancellation signal.

As a method to avoid this problem, a method is known in which a delay circuit is inserted between the voltage controlled oscillator and the phase comparator to provide a delay equivalent to that of the bandpass converter. According to this method, even if the frequency of the interference wave fluctuates, the fluctuation of the passing phase of the band wave generator is canceled by the fluctuation of the passing phase of the delay circuit, so that the frequency of the constant wave signal output from the voltage controlled oscillator The phase does not change.

By the way, just as a band waver is required for a narrowband wave circuit, a band wave waver is also required for orthogonal multiplication to obtain a control signal. That is, in order to improve the input C/N of the orthogonal multiplier circuit by suppressing components other than the residual interference waves from the output signal and to operate the orthogonal multiplier circuit stably, a narrowband filter with a narrow band is required.

When the frequency of the interference wave fluctuates, the passing phase of the bandpass waver fluctuates, and the phase of one of the inputs of the multiplier circuit fluctuates, so that a correct control signal cannot be obtained due to this phase fluctuation.

[Problem that the invention seeks to solve]

As explained above, conventional interference wave removal devices are
There is a drawback that if the frequency of the interference wave changes, a correct control signal cannot be obtained and the degree of interference wave suppression deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide an interference wave removal device that solves the above-mentioned drawbacks and does not deteriorate the degree of interference wave suppression even if the frequency of the interference wave changes.

[Means for solving problems]

The interference wave removal device of the present invention includes: a band waver that suppresses components other than the interference wave of an input signal including an interference wave; and a phase comparator that compares the phases of the output of the band wave waver and the output of the delay means. a low-frequency wave generator that band-limits the output of the phase comparator, a variable oscillator whose oscillation frequency is controlled by the output of the low-frequency wave generator, and a delay equivalent to the delay of the band wave generator for the output of the variable oscillator. an interference wave extraction circuit comprising: the delay means for giving the input signal; an amplitude phase control circuit for controlling the amplitude and phase of the output of the variable oscillator of the interference wave extraction circuit by a control signal; A subtracter that subtracts the output of the control circuit; and a control signal generation circuit that obtains the control signal by orthogonally multiplying the output of the delay means of the interference wave extraction circuit and the output of the subtracter. be done.

〔Example〕

The present invention will be described in detail below with reference to 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.
2. Amplitude error signal 106 and phase error signal 10
7 and outputs a cancellation signal 104 from the input signal 101;
a subtracter 3 that subtracts and outputs an output signal 105;
The extracted interference signal 103 and output signal 105 are input, and the amplitude error signal 106 and phase error signal 107 are input.
The control signal generating circuit 4 outputs a control signal generating circuit 4.

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 amplitude and phase control circuit 2 includes a variable phase shifter 21 that shifts the phase of the extracted interference signal 102 under the control of a phase error signal 107, and a variable phase shifter 21 that attenuates the output of the variable phase shifter 21 under the control of an amplitude error signal 106 to generate a canceling signal. 104.

The control signal generation circuit 4 is a bandpass filter 4 that receives the output signal 105 and suppresses components other than residual interference waves.
1, a π/2 phase shifter 42 that shifts the phase of the extracted interference signal 103 by π/2, and a multiplier that multiplies the output of the bandpass filter 41 and the extracted interference signal 103 and outputs the multiplication result as an amplitude error signal 106. 43, and a multiplier 44 that multiplies the output of the bandpass filter 41 and the output of the π/2 phase shifter 42 and outputs the multiplication result as a phase error signal 107.

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 operations of the amplitude phase control circuit 2 and the subtracter 3 will be explained.

The amplitude and phase of the extracted interference signal 102 are controlled by the amplitude and phase control circuit 2, and the cancellation signal 104 becomes a signal having the same amplitude and phase as the interference wave included in the input signal 101. The subtracter 3 combines the input signal 101 and the cancellation signal 104 in an antiphase relationship, so that
The interference waves included in the input signal 101 are suppressed, and an output signal 105 in which the interference waves have been suppressed is output. Even if the frequency of the interference wave changes, the phase of the extracted interference signal 102 does not change, so the phase control by the variable phase shifter 21 does not become difficult.

The control signal generation circuit 4 operates as explained below.

The bandpass filter 41 improves the C/N of the residual interference waves input to the multipliers 43 and 44. When the frequency of the interference wave, that is, the frequency of the residual interference wave fluctuates, the passing phase of the bandpass filter 41 fluctuates, so the phase of the inputs to the multipliers 43 and 44 also fluctuates by the amount of this phase fluctuation. The delay characteristics of the band wave generator 41 are made to be equivalent to the delay characteristics of the band wave generator 11. In this way, since the extracted interference signal 103, which is another input of the multiplier 43, has a phase variation equal to the phase variation of the output of the bandpass filter 41, the two inputs of the multiplier 43 The phase fluctuations cancel each other out, and the multiplier 43 multiplies the interference wave at the input of the subtracter 101 and the in-phase component of the residual interference wave at the output with the correct phase relationship, and the output is the amplitude error signal. 106 is a signal representing the amplitude error of the cancellation signal 104. Similarly, the multiplier 44 multiplies the interference wave and the orthogonal component of the residual interference wave by the correct phase relationship due to the action of the π/2 phase shifter, and the output thereof, the phase error signal 107, becomes the cancellation signal 104. The signal represents the phase error of

The amplitude error signal 106 and phase error signal 107 are
The input signal 10 is fed back to the variable attenuator 22 and the variable phase shifter 21, and is processed by a loop consisting of the amplitude phase control circuit 2, the subtracter 3, and the control signal generation circuit 4.
1 interference wave is suppressed. Moreover, this degree of suppression does not change even if the frequency of the interference wave changes.

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 can obtain a correct control signal even if the frequency of the interference wave fluctuates. This has the effect that it is possible to provide an interference wave removal device that does not deteriorate the degree of suppression.

[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...Amplitude phase control circuit, 3...Subtractor, 4...Control signal generation circuit.

Claims (1)

[Scope of Claims] 1. A band waver that suppresses components other than the interference wave of an input signal including an interference wave, a phase comparator that compares the phases of the output of the band wave waver and the output of the delay means, and the phase a low-frequency wave generator that band-limits the output of the comparator; a variable oscillator whose oscillation frequency is controlled by the output of the low-frequency wave generator; and a delay equal to the delay of the band wave generator to the output of the variable oscillator. an interference wave extraction circuit comprising the delay means; an amplitude phase control circuit that controls the amplitude and phase of the output of the variable oscillator of the interference wave extraction circuit by a control signal; and a control signal generation circuit that obtains the control signal by orthogonally multiplying the output of the delay means of the interference wave extraction circuit and the output of the subtracter. Characteristic interference wave removal device.