JPS6277720A - Interference wave eliminating device - Google Patents

Abstract

PURPOSE:To eliminate sufficiently an interruption wave by extracting an interference wave signal from an input signal when a digital transmission system receives interference from the FM transmission of the same frequency band, controlling the amplitude and phase, subtracting the output from the interference wave and multiplying the subtraction output with the input or the interference wave signal orthogonally. CONSTITUTION:After the frequency and phase are controlled from the input signal 101 by an interference wave extraction circuit 1 and the frequency of extracted intereference waves 102, 103 is made coincident with the interference frequency by the phase locked loop. Further, the amplitude and phase of the signal 102 pass through a control circuit 2 and become a cancellation signal 104 to form a signal where the amplitude and phase of the interference wave included in the input signal 101 are equal. They are synthesized in opposite phase by a subtractor 3 to generate a suppression signal 105. On the other hand, the interference signal 103 is multiplied to cancel the phase of the input mutually and generation of error signals 106, 107 having equal amplitude error and phase error to the offset signal 104 are urged. Further, the signals are fed back to the control circuit 2 to suppress gradually the input signal 101 to enhance the suppressing effect independently of the frequency fluctuation of the interference wave.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an interference wave removal device, and in particular,
The present invention relates to an interference wave removal device used in a microwave digital transmission system in which M interference waves exist.

[Conventional technology]

When 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 wave.

One of the conventional examples of such an interference wave removal device is disclosed in Japanese Patent Application Laid-open No. 58-1.
Some of them are described in Japanese Patent No. 31853.

In this conventional example, an interference wave signal is extracted from an input signal containing an interference wave by a narrowband Oki wave circuit, the amplitude and phase of the extracted interference wave signal are controlled by a control signal to create a cancellation signal, and a cancellation signal is generated from the input signal. is subtracted to obtain an output signal with interference waves 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.
These error signals become control signals.

A phase-locked loop that is phase-locked to an interference wave is known as a means for realizing a narrowband p-wave circuit. That is, the interference wave component is extracted from the human input signal using a bandpass transducer, the phase of the interference wave component and the output of the voltage controlled oscillator are compared using a phase comparator, and the frequency of the voltage controlled oscillator is controlled using the phase difference output. An interference wave signal is obtained. The bandwidth of the narrow-band offshore wave circuit is determined by the bandwidth of the low-frequency offshore wave device that limits the band of the phase difference output. The bandwidth of the bandpass filter is the input C of the phase comparator.
/N must be improved to make it narrow enough for the phase-locked loop to operate stably.

Now, in the narrowband F-wave circuit using the above means, it is necessary to make the band F-wave device for extracting the interference wave component narrow-band, and when the frequency of the sensuous wave changes, the passing phase of this band R-wave device changes greatly. With this phase variation, the phase of the interference wave signal output from the voltage controlled oscillator also varies greatly, making it difficult to control the phase 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 the delay of the band F wave generator. According to this method, even if the frequency of the interference wave fluctuates, the fluctuation of the passing phase of the F-band wave generator is canceled by the fluctuation of the passing phase of the delay circuit, so that the sensual wave signal that is the output of the voltage controlled oscillator is The phase of does not change.

By the way, just as a bandpass filter is required for a narrowband F-wave circuit, a bandpass p-channel filter 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 narrow band transducer is required.

When the frequency of the interference wave fluctuates, the passing phase of this band ν wave generator 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 to be Solved by the Invention 1] As explained above, the conventional interference wave removal device has the disadvantage that when the frequency of the interference wave changes, the 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 offset waveform device 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 waveform generator and the output of the delay means; a low frequency F for band-limiting the output of the phase comparator;
a variable oscillator whose oscillation frequency is controlled by the output of the low-band p-wave generator, and the delay means for giving the output of the variable oscillator a delay equivalent to the delay of the band p-wave generator. an extraction circuit; an amplitude phase control circuit that controls the amplitude and phase of the output of the variable oscillator of the interference wave extraction circuit using a control signal; a subtracter that subtracts the output of the amplitude phase control circuit from the input signal; and a control signal generation circuit that obtains the control signal by orthogonally multiplying the output of the delay means and the output of the subtracter of the interference wave extraction circuit.

〔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. 1 includes an interference wave extraction circuit 1 which inputs an input signal 101 containing an interference wave and outputs extracted interference signals 102 and 103, and an extracted interference signal 102 and an amplitude error signal 106.
and an amplitude phase control circuit 2 which inputs the phase error signal 107 and outputs a cancellation signal 104, and a subtracter 3 which subtracts the cancellation signal 104 from the input signal 101 and outputs an output signal 105.
and a control signal generation circuit 4 which inputs the extracted interference signal 103 and the output signal 105 and outputs an amplitude error (g signal 106 and a phase error signal 107).

1 interference wave extraction circuit, a band O wave device 11 that inputs an input signal 101 and suppresses components other than interference waves, and a band P wave device 11
・A phase comparator 12 that compares the phases of the outputs of 15, and an output f of the phase comparator 12: a low-frequency wave transducer 13 that limits the band, and a voltage-controlled oscillator 14 whose frequency is controlled by the output of the low-frequency wave transducer 13. , and a band-pass transducer 15 that gives the output of the voltage-controlled oscillator 14 a delay equivalent to the delay of the band-p-wave generator 11. (2) The output of the pressure-controlled oscillator 14 and the low-frequency wave transducer 15 is branched to become extracted interference signals 102 and 103.

Two amplitude and phase control circuits include a variable phase shifter 21 that is controlled by a phase error signal 107 to shift the phase of the extracted interference signal 102, and a variable phase shifter 21 that is controlled by an amplitude error signal 106 and attenuates the output of the variable phase shifter 21 to produce a canceling signal. 104.

4 control signal generation circuits, a band waver 41 which inputs the output signal 105 and suppresses components other than residual interference waves, a π/2 phase shifter 42 which shifts the phase of the extracted interference signal 103 by π/2, and a band p a multiplier 43 that multiplies the output of the wave generator 41 and the extracted interference signal 103 and outputs the multiplication result as an amplitude error signal 106;
and a multiplier 44 that multiplies the output of the band wave transducer 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 band p-wave converter 11 improves the C/N of the interference wave input to the phase comparator 12. Phase comparator 12/low frequency wave transducer 13
Due to the action of the phase-locked loop consisting of the voltage controlled oscillator 14 and the bandpass transducer 15, the frequency of the extracted interference signals 102 and 103 matches the frequency of the interference wave output from the bandpass transducer 11. The bandwidth of the extracted interference signals 102 and 103 can be determined by the low-frequency wave transducer 13. The phase of the extracted interference signal 103 matches the phase of the output of the bandpass transducer 11, and if the frequency of the interference wave changes, the passing phase of the bandpass transducer 11 changes, so the extracted interference signal 103 is adjusted by this phase variation. The phase also changes. On the other hand, since the passing phases of the band p-wave filters 11 and 15 cancel each other out, even if the frequency of the interference wave changes, the phase of the extracted interference signal 1020 does not change. In addition, since the band p-wave device 15 functions to cancel the delay characteristics of the band-wave transducer 11, a delay circuit whose delay characteristics are equivalent to that of the band-wave transducer 11 is used instead of the band-p-wave transducer 15. You can also do that.

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. Subtractor 3
suppresses the interference waves included in the input signal 101 by combining the scar signal 101 and the cancellation signal 104 in an antiphase relationship, and outputs an output signal 105 in which the interference waves are suppressed. 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 band transducer 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 changes, the passing phase of the bandpass transducer 41 changes, so the multiplier 43.
The phase of the 44 inputs also varies. The delay characteristics of the band oscilloscope 41 are made to be equivalent to the delay characteristics of the band p-wave oscillator 11. In this way, 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 band P-wave generator 41. The multiplier 43 multiplies the interference wave at the input of the subtracter 1010 and the in-phase component of the residual interference wave at the output in a correct phase relationship by canceling out the magnitude of the phase fluctuation of the input, and outputs an amplitude error signal. 106
This signal represents the amplitude error of the offset 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 its output, the phase error signal 107, is a cancellation signal. This is a signal representing the phase error of 104.

The amplitude error signal 106 and phase error signal 107 are fed back to the variable attenuator 22 and variable phase shifter 21, and the interference wave of the input signal 101 is generated by a loop consisting of the amplitude phase control circuit 2, subtractor 3, and control signal generation circuit 4. 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 drawings]

FIG. 1 is a block diagram showing an embodiment of an interference wave removal device of the present invention. 1... Interference wave extraction circuit, 2... Amplitude phase control circuit, 3... Subtractor, 4... Control signal generation circuit. Agent Patent Attorney Shinno Uchihara\,-

Claims (1)

[Scope of Claims] A bandpass filter 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 bandpass filter and the output of the delay means; a low-pass filter that band-limits the output of the phase comparator; a variable oscillator whose oscillation frequency is controlled by the output of the low-pass filter; and an output of the variable oscillator that is equivalent to the delay of the bandpass filter. an interference wave extraction circuit comprising: the delay means for providing a delay; an amplitude phase control circuit that controls the amplitude and phase of the output of the variable oscillator of the interference wave extraction circuit using 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. Characteristic interference wave removal device.