JPH0446492B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention is directed to frequency modulation or angle modulation such as phase modulation of FM broadcast waves mixed into a desired received amplitude modulated signal wave such as television broadcast waves due to abnormal propagation. The present invention relates to a reception method for removing interference angle modulated waves that removes interference waves, and is capable of almost completely removing interference angle modulation waves without substantially damaging a desired received amplitude modulated signal wave.

Prior Art Conventionally, in order to remove this type of interference angle modulated wave and receive a desired received amplitude modulated signal wave, a receiving method was used in which a notch filter was used exclusively to remove the main components of the interference angle modulated wave in the band. . In this way, if the interfering angle modulated wave with a spread frequency band is sufficiently removed, the desired signal component within the same band will also be removed at the same time, causing secondary distortion in the received signal, and the overall There was a drawback that resulted in a reduction in the quality of the received signal. In order to cancel out and remove only the interfering angle modulated wave without eliminating the desired signal component, the levels and phases of the antenna outputs from a plurality of appropriately spaced antennas are adjusted appropriately. Conventionally, a receiving method has been used in which a null point is provided in the antenna directivity through synthesis, and the direction of the null point is made to match the arrival direction of the interfering angle modulated wave. The direction of arrival of interfering angle-modulated waves such as FM broadcast waves that are mixed in with the antenna may fluctuate, so there is a drawback that the direction of the antenna null point needs to be readjusted all the time. Another drawback was that it would not be possible to fully deal with the situation if they arrived at the same time.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks, to eliminate any substantial damage to the desired received signal waves, and to eliminate the interfering angle modulated waves almost completely without any adjustment. An object of the present invention is to provide a reception method for removing interference angle modulated waves that can be removed from received signal waves.

That is, the interfering angle modulated wave removal reception method of the present invention actively receives and demodulates the interfering angle modulated wave mixed into the received signal wave, and negative-feeds back the demodulated output to apply inverse modulation to the entire received signal wave. , the interfering angle modulated wave is converted into a band-compressed signal with a small frequency deviation and removed from the restored received signal,
A received amplitude modulated signal wave mixed with a disturbance angle modulated wave is frequency-converted by the oscillation output of a voltage-controlled local oscillator to form first and second converted output waves, and the first converted output wave is converted into the first converted output wave. Angle demodulation detection is performed on the inversely converted output wave whose frequency has been inversely converted by the oscillation output of the voltage controlled local oscillator through a bandpass filter whose passband is the band of the sideband component mixed with the interference angle modulated wave of the output wave. By controlling the oscillation output frequency of the voltage-controlled local oscillator by negative feedback of the demodulated output obtained by , extracting the sideband component mixed with the interference angle modulated wave in which the occupied band of the second converted output wave is compressed through a filter corresponding to the bandpass filter, and extracting the sideband component mixed with the interference angle modulated wave in which the occupied band is compressed; The first converted output wave is equal-amplitude and anti-phase synthesized with the second converted output wave through a narrow band pass filter whose pass band is the band of the angle modulated wave.
A disturbance angle modulated wave in which the occupied band is compressed is obtained from the frequency conversion output sideband component extracted through the filter of the conversion output wave of the first and second
After canceling and eliminating the converted output waves of It is characterized by the fact that it is made to do so.

Note that restoration here refers to converting the frequency of the input signal using the same local oscillation output, and then inversely converting the input signal to return it to the original frequency.

EXAMPLES The present invention will be explained in detail below using examples with reference to the drawings.

The interference angle modulated wave removal reception method of the present invention first compresses the band of the interference wave and removes it when removing the interference angle modulation wave whose band is expanded by modulating the interference wave itself from the received signal. Even if deletion of the desired signal component occurs due to
The purpose is to remove interference waves with a narrow bandwidth, and the circuit system shown in FIG. 1 is conventionally known for band compression of angle modulated waves, which is the starting point of interference wave removal by the method of the present invention. In the angle modulated wave band compression circuit device having the configuration shown in the figure, an input angle modulated wave such as an FM broadcast wave is guided to the multiplier 1, and multiplied by the oscillation output of the voltage controlled oscillator 6, thereby localizing the oscillation output. Frequency conversion is applied as oscillation, and the converted output of either the upper or lower sideband taken out via the bandpass filter 3 is led to the multiplier 2, and the same oscillation output as described above of the voltage controlled oscillator 6 is used as the local oscillation. performs reverse frequency conversion, similarly restores the input angle modulated wave via the bandpass filter 20, and transmits the angle modulated wave restored by such frequency conversion and its inverse conversion to the limiter 4 and
The signal is sequentially guided to the FM detection circuit 5 for demodulation, and the demodulated output is negatively fed back to the voltage controlled oscillator 6 via the low-pass filter 7 to follow the demodulated output signal and therefore the frequency deviation of the input angle modulated wave. multipliers 1 and 2 by changing the local oscillation frequency.
By compressing the bandwidth of the converted output wave and the inversely converted output wave respectively obtained from , and increasing the negative feedback rate, it is possible to localize only to the center carrier frequency component.

That is, when the frequency of the received input signal wave supplied to the input terminal 8 is _i + Δ and the bandwidth determined by the frequency deviation Δ is compressed, the oscillation frequency of the voltage controlled oscillator 6 is _l , and the multiplier 1 When the frequencies of the conversion output and the inverse conversion output of 2 and 2 are respectively ₁ and ₂ , the following relationship holds true, for example: ( _i + Δ) − _l = ₁ (1) ₁ + _l = ₂ (2). From these equations (1) and (2), _i + Δ= ₂ (3). Therefore, regardless of the local oscillation frequency _l , the inverse conversion output frequency ₂ of the multiplier 2 is
The received input signal wave is always equal to the received input signal frequency _i + Δ, and the received input signal wave is restored as the inversely transformed output. When the demodulated output of this restored received input signal wave is applied to the voltage controlled oscillator and the local oscillation frequency _l is controlled by negative feedback, the feedback coefficient is set to α, and the center frequency of the change range due to the negative feedback control of the voltage controlled oscillation frequency is _{set to p.} , the local oscillation frequency _l is _l = _p + α・Δ (4). Substituting this equation (4) into equation (1) and organizing it, we get
The following equation (5) is obtained.

( _i + _p ) + (1-α)・Δ= ₁ (5) Therefore, when the feedback coefficient α=0, the frequency deviation Δ of the received input signal wave is directly applied to the bandpass filter 3. When the feedback coefficient α=1, the frequency deviation Δ of the received input signal wave is compressed and removed, and only the converted output carrier frequency component is applied to the bandpass filter 3. That is, the carrier frequency _i of the received input signal wave is converted to the conversion output center frequency ₁ , and appears in the conversion output as a single carrier wave with no frequency deviation. An unmodulated carrier signal appears.

In one embodiment of the interference angle modulated wave removal method of the present invention, the above-mentioned angle modulated wave band compression is applied to the interference angle modulated wave mixed in the received signal wave, so that the interference wave becomes an unmodulated carrier wave. At the same time, the same signal processing is applied to the entire received signal wave to compress the interference wave mixed band, and by combining both with equal amplitude and antiphase, the interference wave is canceled out and removed in the state of an unmodulated carrier wave. Configure a receiving circuit for wave removal.

FIG. 2 shows an example of the configuration of a receiving circuit for removing interference waves according to the method of the present invention. In the circuit configuration shown in the second diagram, the circuit part shown surrounded by a broken line frame is configured exactly the same as the circuit configuration shown in the first diagram, and this circuit part first allows interference to be mixed into the received signal wave. The angle modulated wave is brought into the state of an unmodulated interfering carrier as described above with respect to FIG.

On the other hand, in the circuit configuration shown in the second diagram, the circuit portion added outside the dashed line frame performs the same signal processing on the entire received signal wave as described above, and then generates unmodulated interference carriers inside and outside the dashed line frame. The configuration is such that equal amplitude and antiphase are combined to cancel each other out.
Note that the center frequency control circuit 16 connected to the voltage controlled oscillator 6 in the circuit portion within the broken line frame is as follows.
This is a circuit portion for controlling the center frequency _p of the range of change of the voltage controlled oscillation frequency due to the above-mentioned negative feedback control. That is, the received input signal wave from the input terminal 8 is guided to the multiplier 11, where it is multiplied by the oscillation output of the voltage controlled oscillator 6, frequency conversion is performed using the oscillation output of the oscillator 6 as a local oscillation, and a bandpass signal is generated. If the filter 12 extracts the converted output located in the same sideband as that within the dashed line frame and supplies it to the subtraction circuit 14, the interference wave component contained in the converted output will be filtered through the bandpass filter within the dashed line frame. It is now in the state of an unmodulated interference carrier wave, which is the same as the interference wave component extracted from No. 3. A narrowband bandpass filter 18 whose pass band is only near the frequency of the unmodulated interfering carrier wave within the dashed line frame.
and level and
Similarly, the subtraction circuit 1 is connected to the subtraction circuit 1 via the delay time adjustment circuit 13.
4 and subtracted from the above-mentioned converted output signal wave to cancel and remove the interference wave. The converted output signal wave whose interference wave components have been canceled out and removed in this way is guided to the multiplier 15, where it is subjected to frequency conversion opposite to that in the multiplier 11 by the same local oscillation from the voltage controlled oscillator 6, and is passed through the bandpass. Filter 17
, the inversely transformed output signal wave having the same band as the received input signal wave is extracted and taken out from the output terminal 19 .

That is, the carrier frequency of the desired received input signal wave is _d , and the frequency of the interference wave is _i as described above.
+Δ, when the feedback coefficient α=1, the frequency of the interference wave component in the conversion output of the multiplier 11
₃ , the frequency deviation Δ disappears and the local oscillation frequency _l becomes the center frequency _p of its range of change, as in the broken line frame, so ₃ = _i − _p (6). On the other hand, the received signal wave in the converted output of the multiplier 11 is generated by the voltage controlled oscillator 6 which generates local oscillation.
Since the oscillation frequency _l is the result of negative feedback control by the interference wave demodulation output, it is subjected to frequency modulation with a frequency deviation Δ, contrary to the interference angle modulated wave, and its frequency _d ′ is _d ′= ( _d −Δ)−do (7). Therefore, since the interference wave frequency ₃ in equation (6) is the same as the unmodulated interference carrier frequency appearing at the terminal 10 within the broken line frame, the interference wave frequency 3 from the terminal 10 is connected to the narrowband bandpass filter 18 and the level/delay time adjustment circuit. The unmodulated interfering carrier wave taken out through the filter 13 and the interfering wave of frequency ₃ mixed in the converted output signal wave from the bandpass filter 12 described above are supplied to the subtracting circuit 14 for subtraction, that is, equal amplitude and antiphase synthesis. If cancellation is removed by , only the converted output signal wave component of frequency _d ′ according to equation (7) will be obtained. The converted output signal wave component is guided to the multiplier 15, and in equation (4) from the voltage controlled oscillator 6, α=
When inverse frequency conversion is performed by local oscillation with a local oscillation frequency _l = _p + Δ set to 1, using equation (7), _d ′+ _l = [ _a − Δ) − _p ] + ( _p + Δ) = _d ( 8) An inversely converted output signal wave with a frequency of Note that since the narrow band band pass filter 18 is for extracting only the unmodulated interfering carrier wave, any narrow band pass filter may be used as long as it does not damage the amplitude information of the unmodulated interfering carrier wave output. can also be used.

In addition, when the carrier frequency _i of the interference wave changes, the center frequency control circuit 16 described above
By simply changing the center frequency _p of the oscillation frequency change range of the voltage controlled oscillator 6 in accordance with the change in the interference wave frequency _i , all other bandpass filters can maintain their passbands fixed. The above-described interference cancellation and cancellation can be performed following the change in the interference carrier frequency _i .

Furthermore, the passband of the bandpass filter 3 within the dashed line frame is approximately the same as the spectral distribution bandwidth of the interfering angle modulated wave, and the passband of the bandpass filter 3 outside the dashed line frame is
The passband of No. 2 is the frequency modulated received signal wave with a frequency deviation Δ obtained as the conversion output of the multiplier 11.
Local oscillation frequency _l of the signal band based on equation (7)
It is sufficient to remove unnecessary sideband components from one of the upper and lower sidebands centered on can be used. It should be noted that if the phase shift caused by the narrowband bandpass filter 18, which seems to interfere with the cancellation and removal of interference waves, is corrected all at once by the level/delay time adjustment circuit 13, there is no need for readjustment thereafter.

Next, by making the center frequency control circuit 16 in the configuration example shown in the second figure respond to the control information related to the interfering carrier frequency, it is possible to automatically follow changes in the interfering carrier frequency and achieve a state where the mixed interfering wave component is zero. FIG. 3 shows an example of a schematic configuration of a receiving circuit according to the method of the present invention in which the signals are converged. The illustrated configuration example shows FM that has crossed the frequency allocation range and mixed into television broadcast waves due to abnormal propagation, etc.
It is configured to automatically remove interference from broadcast waves. That is, the beat frequency corresponds to the difference between the interference wave frequency included in the detected output video signal of the video detection circuit 21 in the television receiver connected to the restored received signal output terminal 19 in the configuration shown in the second diagram and the video carrier frequency. The component is detected by a beat detection circuit 23 to which the detected output video signal is supplied via an amplifier circuit 22. The beat detection circuit 23 is supplied with a synchronization signal separated and extracted by the synchronization separation circuit 24 that has supplied the video signal from the amplifier circuit 22, and is used to detect accurate synchronization signals that depend only on the interfering carrier frequency, which is not affected by the video content. Detect the beat frequency in the synchronization signal section. A voltage proportional to the beat frequency of the detection output is obtained and supplied to the center frequency control circuit 16 described above, so that the frequency of the converted interfering carrier wave from the multiplier 1 is set to a predetermined value, regardless of fluctuations in the beat frequency. If the center frequency _p of the local oscillation frequency change range is automatically controlled so that the interference wave can be automatically tracked and removed.

In the configuration example shown in the second diagram, for convenience of explanation, the multiplier 1 and the multiplier 11 are configured in exactly the same manner and operate in the same way inside and outside the broken line frame.
Although two frequency conversion stages consisting of Of course.

Effects As is clear from the above explanation, according to the present invention, the spectral distribution range of the interfering angle modulated wave mixed into the general received input signal wave is significantly localized, and ultimately converted into a single interfering carrier wave. Since the interfering interference waves are removed by using the cancellation method described in the previous embodiment, there is no adverse effect on the desired signal wave component than when interfering interfering waves are removed in the original band. When used, a special effect can be obtained in that interference waves can be removed while substantially ignoring phase distortion and damage to video signal components. In addition, the interfering angle modulated wave can be removed stably and reliably using a simple circuit device using inexpensive circuit components without requiring particularly precise adjustment.

Note that when the receiving method of the present invention is applied to, for example, removing FM broadcast waves mixed in the received signal of television broadcast waves, the FM detection circuit 5 shown in FIG.
The video signal component will mix into the demodulated FM broadcast wave signal and degrade the S/N of the demodulated FM broadcast wave signal, but since the interference wave that should be canceled out is the angle modulated wave. The S/N deterioration of such a demodulated FM broadcast wave signal is reduced by the so-called FM improvement degree, and as the intensity of the interference wave increases, the degree of S/N deterioration due to the video signal component is reduced.

Furthermore, by cascading multiple stages of interference angle modulated wave removal receiving circuits according to the present invention, each corresponding to a different interference carrier frequency _i , multiple types of interference angle modulation waves mixed in the received signal wave can be reliably removed. Furthermore, if the center frequency _p of the oscillation frequency variation range of the voltage controlled oscillator used as a local oscillator is appropriately controlled, the interfering angle modulated wave within a wide frequency range can be automatically tracked and removed without adjustment. It is also possible to realize an automatic tracking and removal circuit device for mixed interference waves.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the angle modulated wave band compression circuit device which forms the basis of the interference angle modulated wave removal reception method of the present invention, and Fig. 2 is the detailed configuration of the interference angle modulated wave removal reception circuit according to the invention method. FIG. 3 is a block diagram showing another example of the structure of a part of the interference wave removal receiving circuit. 1, 2, 11, 15...multiplier, 3, 12, 1
7, 20...Band pass filter, 4...Limiter,
5...FM detection circuit, 6...Voltage controlled oscillator, 7...Low pass filter, 8...Input terminal, 9, 10, 19
...Output terminal, 13...Level/delay time adjustment circuit,
14... Subtraction circuit, 16... Center frequency control circuit, 1
8...Narrowband bandpass filter, 21...Video detection circuit, 22...Amplification circuit, 23...Beat detection circuit,
24...Synchronization separation circuit.

Claims (1)

[Claims] 1. A received amplitude modulated signal wave mixed with a disturbing angle modulated wave is frequency-converted by the oscillation output of a voltage controlled local oscillator to form first and second converted output waves, Inverse conversion in which the frequency of the converted output wave is inversely converted by the oscillation output of the voltage controlled local oscillator through a bandpass filter whose pass band is the band of the sideband component mixed with the disturbance angle modulated wave of the converted output wave. By controlling the oscillation output frequency of the voltage controlled local oscillator by negative feedback of the demodulated output obtained by angle demodulation detection of the output wave, the interfering angle modulated wave mixed into the first and second converted output waves is generated. compressing the occupied band of the second conversion output wave, and extracting sideband components mixed with the jamming angle modulated wave in which the occupied band of the second converted output wave is compressed, through a filter corresponding to the bandpass filter, The first converted output wave is equal-amplitude and anti-phase synthesized with the second converted output wave through a narrow band pass filter whose pass band is the band of the jamming angle modulated wave whose occupied band has been compressed. After the interference angle modulated wave whose occupied band has been compressed is canceled and removed between the first and second converted output waves from the frequency conversion output sideband component extracted through the filter of the second converted output wave. , the output wave obtained by removing the interference is inversely frequency-converted by the oscillation output of the voltage controlled local oscillator to restore the received amplitude modulated signal wave in which the interference angle modulated wave is not mixed. Modulated wave removal reception method. 2. In the receiving system according to claim 1, the center frequency of the oscillation frequency range of the voltage controlled local oscillator which is subjected to negative feedback control by the demodulated output is set to the carrier wave of the received amplitude modulated signal wave and the interference angle modulated wave. An interfering angle modulated wave removal receiving system characterized in that the negative feedback control is performed in accordance with a beat frequency generated in the detected output of the received amplitude modulated signal wave by amplitude detection of the mixed wave.