JP2549658B2 - Interference elimination type television receiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal interference elimination type receiver, and more particularly to a television receiver which eliminates the interference wave of an FM wave modulated by voice or the like. It is a thing.

(Prior Art) Conventionally, in order to remove an interfering wave mixed in a television broadcast wave, a band elimination filter having a narrow bandwidth, that is, a so-called notch filter is inserted in an intermediate frequency stage of a receiver to interfere as much as possible. There is a method of removing only the interference wave component.

In addition, as another method, the received waves from two or more receiving antennas arranged close to each other are relatively adjusted in amplitude and phase and are combined, so that the null direction of the directivity of the formed receiving antenna as a whole is determined. There is a system that removes an interference wave by matching it with the arrival direction of the interference wave (for example, Kawai et al., "For Foreign Radio Interference Removal Device by Sporadic E Layer", Television Engineering RE82-26, 1982).

Furthermore, a method of subtracting and removing an interfering component by utilizing the fact that only the interfering wave component can be taken out has been put into practical use, when a video signal is not detected when quadrature synchronous detection is performed on both sideband transmission areas of a television (for example, Arada et al., "TV-band interference wave removal device based on sporadic E layer", TV magazine Vo
l.40, No.8, 1986).

(Problems to be Solved by the Invention) Depending on the interfering wave removing means such as inserting the notch filter in the intermediate frequency stage of the receiver to remove only the interfering interfering wave component, the frequency of the interfering wave is close to the video carrier. If the notch filter is inserted, the disturbing wave is removed and, as a result, the disturbing disturbing wave and the beat component of the image carrier are removed, but the notch filter simultaneously removes the image signal component near the disturbing wave. Since it is lost, it is difficult to sufficiently improve the reception image quality.

Further, in the method of removing the interfering wave by matching the directivity null direction with the interfering wave arrival direction by synthesizing the received waves of two or more receiving antennas, if the arrival direction of the interfering wave changes each time, There was a drawback that readjustment in the null direction had to be performed.

Furthermore, in the case of the method of quadrature-coherently detecting a television signal and extracting only the interfering wave component, and then performing the Hilbert transform to subtract and remove the interfering component, the interfering wave is generated in the area where the television is transmitting single sideband. When mixed, it is equivalent to the insertion of a notch filter, resulting in distortion in the video signal.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and remove unnecessary FM radio waves such as foreign radio wave interference waves based on the Sporadic E layer, citizen band radio wave spurious interference, and amateur radio wave spurious interference. It is an object of the present invention to provide an interference elimination type television receiving device capable of improving the interference of television radio waves and performing high quality television reception.

(Means for Solving the Problems) In order to achieve this object, an interference cancellation type television receiving device of the present invention is provided with a circuit for gating a horizontal synchronizing signal section of a received television signal and a circuit for gated the same. FM
A circuit for demodulating an intermittent interference wave and reproducing a baseband signal of a continuous interference wave by an interpolation filter, and a first obtained by comparing the phase of a gated interference wave and a carrier of the reproduced continuous interference wave. From two loops sharing a voltage controlled oscillator controlled by the sum of the phase comparison output and a second phase comparison output obtained by phase comparing the gated disturbance and the regenerated continuous disturbance. And a circuit for regenerating the carrier of the continuous interference wave having a PLL circuit, and re-modulating the reproduced carrier of the continuous interference wave with the regenerated baseband signal of the continuous interference wave. And a circuit for reproducing the signal, adjusting the amplitude and phase of the reproduced continuous interference wave and subtracting it from the received television signal to remove the FM interference wave from the received television signal. And it is characterized in and.

(Operation) The present invention is based on the Nyquist sampling theorem that a signal in a band of 1/2 or less of the frequency f _H of the horizontal synchronizing signal is completely restored when the interference wave is sampled at the horizontal synchronizing signal period of the television signal. It was made based on.

That is, the present invention is designed to eliminate unnecessary FM in television signals.
When a modulated interfering wave is mixed in, only the interfering wave is gated and extracted without being affected by the video signal in the horizontal sync signal section, FM demodulated, and passed through the interpolation filter to obtain a complete interfering baseband signal. Play and PL consisting of two loops
The carrier of the interference wave reproduced using the L circuit is re-modulated with this baseband signal, the phase and amplitude are adjusted, and then the interference wave is automatically subtracted by subtracting it from the television signal containing the interference wave. It is removed to obtain a high quality TV image.

FIG. 1 shows a block diagram of the basic configuration of a receiver for explaining the principle of the present invention. The operation of the receiving apparatus of the present invention will be described with reference to FIG. The IF signal of the received television radio wave is detected by the video detection circuit 1 by a normal method, then guided to the gate circuit 2, and the horizontal sync signal obtained by the sync separation circuit 3 causes an interference wave existing in the horizontal sync signal section. Remove the ingredients. The disturbing wave exists over the entire television signal on the time axis, but since there is no video signal component in the horizontal synchronizing signal section, only the disturbing wave component can be taken out although it is discontinuous in time. When the extracted interference wave component is FM-detected by the interference wave detection circuit 4, the baseband signal of the intermittent interference wave is demodulated. This is reproduced through an interpolation filter 5 to reproduce a continuous perfect interference wave baseband signal.

According to the Nyquist sampling theorem, the upper limit of the baseband signal frequency of the reproduced disturbance wave must be 1/2 or less of the horizontal sync signal frequency of 15.75 kHz, that is, 7.875 kHz or less, but the human voice spectrum is sufficient. It is in this range, and the spectrum of a general musical tone is considered to be approximately 7 kHz or less (Ehara et al., Spectral Level Distribution of Orchestra Performers, NHK Technical Research, Vol. 22, No. 6, No. 121, Vol. 121, 1970), except for the case where the interfering wave is a stereo FM broadcast wave, the signal can be reproduced almost completely.

The output of the gate circuit 2 is added to an interfering wave carrier regenerating circuit 6 composed of, for example, a limiter and a PLL circuit, and the regenerated interfering wave carrier is remodulated by the interfering wave baseband signal obtained from the interpolation filter 5. To remodulate. Since this re-modulated signal is exactly the same as the interfering wave signal mixed in the video signal, if the subtracting circuit 9 subtracts the video signal corrected by the delay of the system for reproducing the interfering wave by the delay circuit 8. , A high-quality television video signal from which an interfering wave component is removed can be obtained.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

First, prior to the description of the embodiments of the present invention, a configuration block diagram of a receiving device when an interfering wave is an AM modulated wave is shown in FIG. 2 and will be described. An AM detection circuit 10 is used as the interference wave detection circuit 4 having the principle configuration shown in FIG. This detection output is introduced into the resample circuit 11, and resampled by a sampling pulse having a width extremely narrower than the gate pulse centered at the center of the gate pulse obtained by the sampling pulse generation circuit 12 to generate in the gate circuit 2. Remove the distortion at the edge of the gate pulse. After a while
The interpolation filter 5 restores the baseband signal of the continuous interference wave, and leads it to the AM modulation circuit 14 via the gain adjustment circuit 13. The modulation degree is adjusted by the gain adjusting circuit 13.

On the other hand, the carrier for modulation is reproduced as follows.
The output of the gate circuit 2 is added to the limiter circuit 15 to eliminate the amplitude fluctuation, and the phase comparison circuit 16 and the sample hold circuit 1
7. Input as the reference signal of the PLL circuit composed of the low pass filter LPF18 and the voltage controlled oscillator 19. As a result, the carrier of the interfering wave is regenerated and output from the voltage controlled oscillator 19. The sample hold circuit 17 is inserted in order to efficiently perform the intermittent PLL operation. The reproduced carrier is added to the AM modulation circuit 14 via the phase adjustment circuit 20.

The output of the AM modulation circuit 14, that is, the interfering wave signal is added to the subtracting circuit 9 via the gain adjusting circuit 21, and is subtracted from the interfering wave in the video signal from the delay circuit 8. A video signal from which is removed is obtained.

In order to perform complete subtraction removal, the phase and amplitude of both must match, and for this reason, the phase adjustment circuit 20,
The gain adjusting circuit 21 adjusts the phase and the amplitude, respectively.

FIG. 3 is a configuration block diagram of an embodiment of the receiving apparatus of the present invention in which the interfering wave is an FM modulated wave. The video signal basebanded by the video detection circuit 1 is added to the gate circuit 2, and the interfering wave mixed in this video signal is gated and taken out by the horizontal sync signal obtained by the sync separation circuit 3 only during this period. FM detection circuit for gated intermittent disturbances 22
After the detection by (1), distortion is removed by the resample circuit 11 as in the second embodiment. The interpolating filter 5 reproduces the continuous interference wave baseband signal, and the gain adjusting circuit 13
The FM modulation circuit 23
Lead to. The signal that is modulated and becomes the same as the interfering wave in the video signal is guided to the subtracting circuit 9, and is subtracted from the main line video signal through the delay circuit 8 to obtain the video signal from which the interfering wave is removed.

The modulating carrier removes the AM component of the output of the gate circuit 2 by the limiter circuit 15, and regenerates it by the PLL circuit including the phase comparison circuit 16, the sample hold circuit 17, the low pass filter LPF 18, and the voltage controlled oscillator 19.

At this time, the interference wave signal input as a reference to the phase comparison circuit 16 via the limiter circuit 15 is an FM signal, and because the period of phase comparison is only the time width of the horizontal synchronization signal, the time constant of the LPF is set to Even with proper selection, it is difficult to obtain a perfect continuous wave (CW) signal that is exactly the same as the undisturbed interfering wave. Therefore, in the present invention in which the interfering wave is an FM modulated wave,
Another PLL circuit that shares the voltage controlled oscillator 19 is configured to extract the complete CW signal from the voltage controlled oscillator. That is, the output of the FM modulation circuit 23 and the output of the limiter circuit 15 are phase-compared by the phase comparison circuit 24, the error voltage is guided to the addition circuit 27 via the sample hold circuit 25 and the LPF 26, and is added to the error voltage from the LPF 18. , The phase comparator circuit 16, the sample and hold circuit 17, the low-pass filter LPF 18, and the voltage-controlled oscillator 19 are operated as a correction signal for incomplete operation of the PLL circuit.

FIG. 4 automatically controls the operations of the gain adjusting circuit 13, the phase adjusting circuit 20 and the gain adjusting circuit 21 in the embodiment of the present invention shown in FIG. 3 to change the level of the interfering wave and the change of the circuit system due to temperature. FIG. 6 is a block diagram of an example configuration of automatic removal that improves the reduction of the removal effect based on the above.

The output of the gate circuit 2 is applied to the FM detection circuit 22 after the amplitude is made constant by the AGC circuit 28. On the other hand, the output of the gate circuit 2 is branched and applied to the level detection circuit 29 to extract the level of the interfering wave, and the gain adjusting circuit is automatically controlled by this voltage to follow the fluctuation of the level of the interfering wave. So that it can be removed. Further, after the interference wave is generated, the output of the subtraction circuit 9 is branched, and the gate circuit 30 gates the horizontal synchronization signal from the synchronization separation circuit 3 to take out the residual interference wave component. The level of this component is detected by the level detection circuit 31, converted into a digital signal by the A / D conversion circuit 32 and taken into the CPU 33, and the gain adjustment circuit 13 and the phase adjustment circuit 20 are provided so that the level of the residual interference wave is minimized. Is controlled from the CPU.

(Effects of the Invention) As described above, by using the interference elimination type television receiving apparatus of the present invention, it is possible to eliminate the interference wave of FM wave which overcomes the drawbacks of the conventional apparatus and is based on the sporadic E layer. It has become possible to remove unnecessary radio waves of 40 dB or more, such as foreign radio wave interference waves, citizen band radio wave spurious interference, and amateur radio wave spurious interference. Further, according to the present invention, since the interference wave is removed at the stage of the baseband video signal, the interference wave does not depend on the arrival direction of the interference wave, and the video signal can be removed without damage. Has the advantage that the image quality of is not deteriorated at all.

Finally, it should be noted that it is obvious to those skilled in the art that the principle and technical idea for achieving the receiving apparatus of the present invention can be applied to facsimile reception.

[Brief description of drawings]

FIG. 1 shows a block diagram of the basic configuration of a receiver for explaining the principle of the present invention, and FIG. 2 shows a block diagram of the receiver when an interfering wave is an AM modulated wave. FIG. 3 shows a block diagram of the configuration of an embodiment of the device of the present invention, and FIG. 4 is a block diagram of an additional circuit for automatically performing the interference wave removal of the embodiment shown in FIG. 1 ... Video detection circuit 2 ... Gate circuit 3 ... Sync separation circuit 4 ... Interference wave detection circuit 5 ... Interpolation filter 6 ... Interference wave carrier regeneration circuit 7 ... Remodulation circuit 8 ... Delay circuit 9 ... … Subtraction circuit 11 …… Resample circuit 12 …… Sampling pulse generator circuit 13,21 …… Gain adjustment circuit 15 …… Limiter circuit 16,24 …… Phase comparison circuit 17,25 …… Sample hold circuit 18,26 …… Low-pass filter LPF 19 …… Voltage controlled oscillator 20 …… Phase adjustment circuit 22 …… FM detection circuit 23 …… FM modulation circuit 27 …… Adding circuit

Claims (1)

(57) [Claims] 1. A circuit for gating a horizontal synchronizing signal section of a received television signal, and a circuit for demodulating an intermittent interfering wave of FM obtained thereby and reproducing a baseband signal of a continuous interfering wave by an interpolation filter. And a first phase comparison output obtained by phase-comparing the gated disturbing wave and the carrier of the regenerated continuous disturbing wave with the gated disturbing wave and the regenerated continuous disturbing wave. And a circuit for regenerating the carrier of the continuous interference wave, which has a PLL circuit composed of two loops sharing a voltage controlled oscillator controlled by an addition output of the second phase comparison output A circuit for remodulating the carrier of the reproduced continuous interference wave with the regenerated baseband signal of the continuous interference wave to reproduce the continuous interference wave, and adjusting the amplitude and phase of the reproduced continuous interference wave. Said subtracted from the received television signal, the received television signal interference removal type television receiver and removing the FM interference waves from Te.