JPH0951547A - Video signal reception device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the threshold expansion effect of a high-saturation signal and prevent the CN ratio of an FM signal from decreasing owing to feedback loop delay as to the video signal reception device of a satellite broadcasting tuner, etc., which employs a tracking filter system. SOLUTION: An FM-demodulated signal 10 is inputted to a chrominance signal trap filter 31 and a chrominance signal BPF 35 respectively and a chrominance subcarrier signal 36 extracted by a chrominance signal BPF 35 is outputted to a phase shifting circuit 37. An adding circuit 40 adds the phase- adjusted chrominance subcarrier signal 38 outputted by the phase shifting circuit 37 and the luminance signal 32 having the chrominance subcarrier component removed by the chrominance signal trap filter 31 together and its output is supplied to a tracking filter 21 as a tracking signal 41 having its phase adjusted through an amplifying circuit 22 to control its center frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal receiving device such as a satellite broadcast tuner, and more particularly to improvement of a video signal receiving device using a tracking filter system.

[0002]

2. Description of the Related Art FIG. 3 shows a circuit configuration example of a general satellite broadcast tuner. In the figure, 1 is an intermediate frequency signal, 2 is a preamplifier, 3 is a first band pass filter (BPF), 4 is a frequency conversion circuit, 5 is a second intermediate frequency signal, 6 is a second intermediate frequency amplification circuit, 7 is a second band pass filter (BPF), 8 is an amplitude limiting circuit, 9 is FM
Demodulation circuit, 10 is an FM demodulation signal, 11 is a tuning voltage, 12
Is a variable local oscillation circuit, and 13 is a local oscillation signal.

A 12 GHz band satellite broadcast signal received by the satellite broadcast antenna is frequency-converted into a first intermediate frequency signal 1 by a BS converter (not shown) and input to the satellite broadcast tuner of FIG. The first intermediate frequency signal 1 is
The gain is controlled in the preamplifier 2 so that the signal level thereof becomes constant, the interfering signal component of the image frequency is removed by the first BPF 3, and then the frequency conversion circuit 4 in the next stage.
Output to In the frequency conversion circuit 4, the local oscillation signal 1 whose oscillation frequency is controlled by the tuning voltage 11 in the variable local oscillation circuit 12 in order to select a desired channel.
3 and the output signal of the first BPF 3 are mixed and subjected to heterodyne detection to perform frequency conversion into the second intermediate frequency signal 5. The second intermediate frequency amplifier circuit 6 controls the gain of the second intermediate frequency signal 5 so as to have a constant signal level, and outputs it to the second BPF 7 in the next stage. The second BPF7 is
Center frequency of the second intermediate frequency signal 5 (about 403 MHz)
With a bandwidth of 27 MHz, which is the satellite broadcast channel bandwidth (≈ Carson's law bandwidth)
(Band pass filter). After the out-of-band signal is removed by the second BPF 7, the FM is controlled by the amplitude limiting circuit 8.
Unwanted AM components in the signal are suppressed and output to the FM demodulation circuit 9. The FM demodulation circuit 9 performs FM detection in order to obtain the FM demodulation signal 10. However, when the FM detection system is the double tuning type detection system, the amplitude limiting circuit 8 in the preceding stage is required, and the PLL ( It is not necessary when using the PhaseLocked Loop) type detection method.

In the FM detection method, there is a phenomenon called a threshold phenomenon in which the SN ratio of the signal after FM demodulation sharply deteriorates when the CN ratio of the received signal is divided by a certain value. There is a tracking filter system (tracking filter system) as one of the systems for improving the threshold phenomenon.

A Carson's law bandwidth is required to pass FM waves through the BPF without distortion. However, looking at the FM wave in a very short time, it can be seen that most of the energy of the FM wave is concentrated in a narrow band around the instantaneous frequency. Therefore, the narrow band BP whose center frequency in the pass band is variable
If F is used and its center frequency is controlled so as to match the instantaneous frequency of the FM wave, the power of noise that passes through this narrow band BPF will be reduced by the amount by which the band is narrowed.
The improvement in the CN ratio of the M wave extends the FM demodulation threshold level. Such a threshold expansion method is called a tracking filter method. FIG.
3 shows the instantaneous frequency of the FM wave and the pass band of the filter when the BPF having the ordinary Carson law bandwidth is used in the tuner of FIG. 3 and when the narrow band tracking filter is used.

FIG. 4 shows an example of a circuit configuration when the tracking filter system is applied to a satellite broadcast tuner. Since the circuit configuration until the frequency is converted to the second intermediate frequency signal 5 in the figure is the same as the circuit configuration of the general satellite broadcast tuner shown in FIG. 3, the second intermediate frequency signal 5 is input here. The following description will be given. In FIG. 5, 21 is a tracking filter, 22 is an amplifier circuit, 23 is a tracking signal, and 24 is a feedback loop. The tracking filter 21 is the second BPF 7 of FIG.
The signal pass band width is narrower than that of, and the center frequency of the signal pass band is controlled by the tracking signal 23. By using a signal obtained by gain-controlling the FM demodulated signal 10 by the amplifier circuit 22 as the tracking signal 23,
The center frequency of the tracking filter 21 is FM
Feedback is applied so as to follow the instantaneous frequency of the wave. The amplifier circuit 22 provides an appropriate gain for feedback and removes unnecessary high frequency noise in the feedback loop 24.

[0007]

A problem with the tracking filter system having the circuit configuration shown in FIG. 4 is that a delay occurs in the feedback loop 24. When the delay amount of the feedback loop is sufficiently small with respect to the time corresponding to 90 ° of the frequency of the modulation signal, the tracking filter 2
It is considered that the center frequency of 1 tracks the instantaneous frequency of the FM wave, but when the loop delay amount becomes larger than the time corresponding to 90 °, the center frequency of the tracking filter 21 deviates from the instantaneous frequency of the FM wave rather. However, the C / N ratio of the FM signal is deteriorated.

The modulation signal in satellite broadcasting is a video signal, and the highest frequency of the video signal is 4.5 MHz, 90 °.
Is approximately 55.6 nsec. Also, NTS
In the C method, the color subcarrier signal having a frequency of about 3.58 MHz is superimposed on the video signal, and the time corresponding to 90 ° of this color subcarrier signal is about 69.8 nsec. Further, in satellite broadcasting, in order to improve the deterioration of the SN ratio in the high frequency component of the demodulation signal due to the triangular noise peculiar to the FM detection method, emphasis is applied to the composite video signal by a circuit having the characteristics shown in FIG. Since the multiplied signal is used as the modulation signal, the high frequency component of the composite video signal is emphasized in this modulation signal as shown in FIG. In FIG. 7, in order from the top, a is a color bar signal, b is a signal obtained by applying emphasis to the color bar signal,
Reference characters c respectively indicate the luminance signal components of the signal obtained by applying emphasis to the color bar signal. It is said that the luminance signal component in the composite video signal has energy concentrated at a statistically low frequency. However, in satellite broadcasting, emphasis is applied to the NTSC composite video signal. As can be seen from the above, the color subcarrier signal component has a very large energy in the modulated signal. From this, when the threshold expansion is performed by the tracking filter method, it is necessary to set the delay amount of the feedback loop 24 to a value sufficiently smaller than the time 69.8 nsec corresponding to 90 ° of the color subcarrier. . However, it is very difficult to reduce the delay amount of the feedback loop to a practical time in an actual circuit, and in the case of an image having a relatively high saturation, the tracking filter method rather deteriorates the CN ratio. The problem arises.

Further, the reduction of the CN ratio in the high frequency region of the luminance signal has not been a solution because the video signal has a property that energy is statistically concentrated in the low frequency. However, this point should be resolved in order to improve the overall image quality. A horizontal edge is an example of an image having a high-frequency luminance signal. FIG.
Although (a) is a display example of an image having a horizontal edge, such a horizontal edge is often found in a character telop or the like. In a system for transmitting a video signal by FM, such as satellite broadcasting, if the CN ratio of the signal at the horizontal edge part is reduced, noise generally called truncation noise is generated in the demodulated signal, which impairs the quality of the displayed image. become.

An object of the present invention is to extend a threshold even in a high saturation signal where a threshold extension effect cannot be expected due to a feedback loop delay in a video signal receiving apparatus employing a tracking filter system, and to cause the feedback loop delay. This is to prevent a decrease in the CN ratio in the FM signal of the high-frequency luminance signal component generated as a result.

[0011]

In order to achieve the above object, the invention of claim 1 is based on a tracking filter to which a received signal converted into an intermediate frequency component is input, and an FM demodulated signal of the received signal. A loop for returning a tracking signal to the tracking filter, and a video signal receiving apparatus for controlling a center frequency in a signal pass band of the tracking filter by the tracking signal, in the feedback loop, The gist is that a phase adjusting means for adjusting the phase of the color subcarrier component is provided.

According to a second aspect of the present invention, in the apparatus of the first aspect, the phase adjusting means includes a color signal trap filter and a color signal bandpass filter to which the FM demodulated signal is applied, and a color signal bandpass filter. A phase shift circuit for adjusting the phase of the color subcarrier signal, and an addition circuit for adding the luminance signal from the color signal trap filter and the phase adjusted color subcarrier signal from the phase shift circuit are configured. There is.

According to a third aspect of the present invention, there is provided a video signal receiving device, which comprises band pass filter means having a variable center frequency and a pass band width to which a received signal converted into an intermediate frequency component is inputted.
A loop for returning a pass band width control signal corresponding to the FM demodulated signal of the received signal to the band pass filter means, and edge detecting means for detecting a horizontal edge from the FM demodulated signal in the feedback loop; A control means for outputting the passband width control signal based on the horizontal edge detection signal from the means to control so as to widen the passband width of the bandpass filter means.

According to a fourth aspect of the present invention, in the apparatus of the third aspect, the horizontal edge detecting means detects a luminance signal passing filter to which an FM demodulated signal is input, and a positive edge detection to which a luminance signal from the filter is input. A circuit for obtaining an edge pulse signal by adding the positive and negative edge pulse signals from the positive and negative edge detection circuits, and a 1H delay from the edge pulse signal. And a delay circuit that outputs an edge pulse signal.

According to a fifth aspect of the present invention, there is provided a video signal receiving apparatus which is responsive to band-pass filter means for varying the center frequency and pass band width of the received signal converted into the intermediate frequency component and the FM demodulated signal of the received signal. A first loop and a second loop for returning the tracking signal and the pass band width control signal to the band pass filter means, and the phase of the color subcarrier component in the FM demodulated signal is provided in the first feedback loop. A phase adjusting means for adjusting and a first control means for outputting the tracking signal from the output of the means and controlling the center frequency in the signal pass band of the band pass filter means by the tracking signal are provided. F in the feedback loop
Edge detecting means for detecting a horizontal edge from the M demodulated signal; and a control for expanding the pass band width of the band pass filter means by outputting the pass band control signal based on the horizontal edge detecting signal from the means. 2 control means,
It is a gist to have.

According to a sixth aspect of the present invention, in the apparatus according to the fifth aspect, the band pass filter comprises a tracking low pass filter and a tracking high pass filter, and the band pass control signal and the tracking signal from the phase adjusting means are used to set the band pass filter. It is configured to control the pass band of each filter.

In the apparatus of the present invention, since the phase of the color subcarrier component of the FM demodulated signal is adjusted, the center frequency of the tracking filter is controlled by the phase adjusted tracking signal. Therefore, even in the FM demodulated signal, particularly in the FM signal of the image signal having a relatively high saturation, the CN ratio is improved and the threshold extension effect can be obtained. Further, the horizontal edge is detected from the FM demodulated signal, and the pass band width of the band pass filter means is controlled based on the horizontal edge detection signal. According to this, the horizontal edge position is predicted by utilizing the vertical correlation of the image, and at the predicted position, the bandwidth of the filter means is returned to the normal Carson rule bandwidth, whereby the CN ratio in the high frequency luminance signal is increased. Can be prevented.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 1, a tracking filter 21 to which the second intermediate frequency signal 5 is input via the second intermediate frequency amplifier circuit 6, and a tracking signal corresponding to the FM demodulated signal 10 of the signal 5 by the FM demodulator circuit 9. In a video signal receiving device including a loop 24 that returns 41 to the tracking filter 21, the FM demodulated signal 1
Phase adjusting means 28 for adjusting the phase of the color subcarrier component of 0
Is provided. As a result, the phase of the tracking signal 41 is adjusted, the center frequency in the signal pass band of the tracking filter 21 is controlled by this signal 41, and the FM signal of the high saturation signal which is not expected to have the threshold expansion effect due to the delay of the feedback loop 24. However, the CN ratio is improved, and the threshold extension effect can be enhanced.

As an embodiment of the invention of claim 2, as shown in FIG. 1, the phase adjusting means 28 includes a color signal trap filter 31, a color signal bandpass filter 35, a phase shift circuit 37 and an adder circuit 40. Consists of.

According to the third embodiment of the invention, as shown in FIG. 8, the center frequency and the pass band width to which the second intermediate frequency signal 5 is input via the second intermediate frequency amplifier circuit 6 are variable. A band pass filter means 50 and a loop 24 'for returning a pass band control signal corresponding to the FM demodulation signal 10 of the signal 5 by the FM demodulation circuit 10 to the means 50 are provided, and an FM is provided in the feedback loop. Video signal reception having edge detection means for detecting horizontal edges from the demodulated signal 10 and control means 27 for outputting the pass band control signal to the filter means 50 based on the horizontal edge detection signal from the edge detection means. It is a device.

As an embodiment of the invention of claim 4, the edge detecting means 26 comprises a luminance signal passing filter 53, a positive edge detecting circuit 55 and a negative edge detecting circuit 56, as shown in FIG. The control means 27 comprises an OR circuit 66 and a 1H delay circuit 60. With such a configuration, it is possible to prevent a decrease in the CN ratio in the FM signal of the high frequency luminance signal due to the feedback loop delay.

In the fifth embodiment of the invention, as shown in FIG. 8, the center frequency and the pass band width to which the second intermediate frequency signal 5 is inputted via the second intermediate frequency amplifier circuit 6 are variable. The video signal receiving device is provided with a bandpass filter means 50 and loops 24 and 24 'for returning a tracking signal 41 and a passband control signal 61 corresponding to the FM demodulated signal 10 of the signal 5 to the filter means 50. In the feedback loop 24, the tracking signal is output from the phase adjusting means 28 for adjusting the phase of the color subcarrier component in the FM demodulated signal and the output of the means 28, and the signal of the filter means 50 is passed by the tracking signal. First control means 25 for controlling the center frequency in the band is provided. Further, in the feedback loop 24 ', an edge detecting means 26 for detecting a horizontal edge from the FM demodulated signal 10 and the pass band control signal based on the horizontal edge detecting signal from the means 26 are outputted to output the pass band control signal. Second control means 27 for controlling so as to widen the pass band width. With such a configuration, the F of a high saturation signal for which the threshold expansion effect cannot be expected due to the feedback loop delay is used.
The CN ratio can be improved even in the M signal, the threshold extension effect can be enhanced, and the CN ratio in the FM signal of the high frequency luminance signal component due to the feedback loop delay can be prevented from lowering. CN of FM demodulated signal and high frequency luminance signal due to
It is possible to prevent the ratio from decreasing.

According to an embodiment of the invention of claim 6, the filter means 50 is a tracking low-pass filter 5.
1 and a tracking high-pass filter 52, the pass band width control signal 61 (1H delay edge pulse signal) and the tracking signal 41 are given to positive and negative pulse adding circuits 62 and 63, and positive and negative pulses are added. The tracking signals 64 and 65 are obtained, and the pass bands of the filters 51 and 52 are controlled thereby.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a video signal receiving apparatus according to the present invention, for example, a satellite broadcast tuner. The same reference numerals as those in FIGS. 3 and 4 represent the same or similar circuits, and particularly, in the present embodiment, in a feedback loop 24, A phase adjusting means including a color signal trap filter 31, a color signal bandpass filter (BPF) 35, a phase shift circuit 37, and an adding circuit 40 is provided, and the phase adjusting means adjusts the phase of the color subcarrier component of the FM demodulated signal 10. I am trying. 32 is a luminance signal, 36 is a color subcarrier signal, 38 is a phase-adjusted color subcarrier signal, 41
Is a tracking signal whose phase is adjusted.

FIG. 2 illustrates the operation of the present invention.
It shows an example of the waveform of the signal. Here, for simplicity of explanation, it is assumed that the required gain in the amplifier circuit 22 is 0 dB. FIG. 2A assumes an ideal waveform of the tracking signal at a certain time. In other words, FIG. 2A can also be regarded as an example of the waveform of the FM demodulated signal 10 when it is assumed that there is no delay in the feedback loop 24. However, the actual FM demodulated signal 10 is output with a constant delay amount T with respect to the ideal tracking signal, as shown in FIG. It has already been described that when the delay amount T cannot be made sufficiently small compared to the time corresponding to 90 ° of the frequency of the modulation signal, if this is used as the tracking signal, the CN ratio is rather lowered. In addition, since the color subcarrier component has a large energy in the modulation signal of satellite broadcasting, it is extremely difficult to make the feedback loop delay amount sufficiently smaller than the time (69.8 nsec) corresponding to 90 ° of this color subcarrier. The difficult things are as described above. Therefore, in the present invention, the phase adjusting means is provided in the feedback loop 24. The FM demodulated signal 10 includes a color signal trap filter 31 and a color signal B.
It is input to each of the PFs 35. Luminance signal 3 from which the color subcarrier signal component has been removed by the color signal trap filter 31
An example of waveform No. 2 is shown in FIG.

On the other hand, the color subcarrier signal 36 in which only the color subcarrier signal component is extracted by the color signal BPF 35 is output to the phase shift circuit 37 of the next stage. The phase shift circuit 37 adjusts the phase of the color subcarrier signal 36 so that the color subcarrier signal component of the tracking signal 41 whose phase is adjusted as described later and the phase of the ideal color subcarrier signal component of the tracking signal match. , Phase-adjusted color subcarrier signal 38 is output.

An example of the waveform of the phase-adjusted color subcarrier signal 38 is shown in FIG. 2 (d). Here, since the delay amount generated in the feedback loop 24 is a constant value, the phase shift amount required for the phase shift circuit 37 is fixed, and therefore the phase shift circuit 37 is a fixed delay line or a phase inversion circuit + fixed. It can be realized with a delay line. Luminance signal 32 and phase-adjusted color subcarrier signal 38
Is added by the adder circuit 40, and the tracking signal 41 whose phase is adjusted is given to the tracking filter 21 via the amplifier circuit 22 to control the center frequency thereof. FIG.
(E) shows an example of the waveform of the tracking signal 41 whose phase has been adjusted. It can be seen that the signal 41 has a very high correlation with the waveform of the ideal tracking signal of FIG. 2 (a).

As described above, since the phase-adjusted tracking signal 41 in the present invention is a signal having a phase close to an ideal phase with respect to the component of the color subcarrier signal, it is relatively saturated as an FM demodulation signal. Even in the case of a high image signal, the threshold expansion effect by the tracking filter method can be obtained. In this case, regarding the luminance signal component, the influence of the phase shift of the tracking signal due to the feedback loop delay remains as it is in the high frequency region, but as already explained, the luminance signal component statistically concentrates energy in the low frequency. Therefore, the above-mentioned influence is relatively small, and the threshold extension effect by the tracking filter method can be expected more comprehensively.

Next, FIG. 8 shows, as another embodiment of the present invention, not only the improvement of the threshold expansion effect in the high chroma signal described above but also the prevention of the decrease of the CN ratio in the FM signal of the high frequency luminance signal component. The structural example of an apparatus is shown. In the figure, the same reference numerals as those in FIG. 1 represent the same or similar circuits, and 50 is the tracking filter 2
1 is band-pass filter means having a variable center frequency and pass-band width, such as a tracking low-pass filter (LPF) and a high-pass filter (HP).
F) 52, and each filter can change its cutoff frequency by a control voltage.

When the control voltages of both filters are the same, the frequency characteristics of both filters are designed to be equal to the characteristics of the tracking filter 21. That is,
In FIG. 8, the signals for controlling the tracking LPF 51 and the tracking HPF 52 correspond to a tracking signal 64 to which a positive pulse is added and a tracking signal 65 to which a negative pulse is added, as will be described later. Phase-adjusted tracking signal 41
8 will operate exactly the same as the embodiment of FIG.

On the other hand, the tracking LPF 51 and the tracking HPF 52 have frequency characteristics as shown in FIG. 10 as described above, and the tracking filter 21 has a center frequency of f ₁ → f ₂ → f _{3 as} shown in FIG. It has a variable center frequency operation characteristic, and as shown in FIG. 11, the normal bandwidth is as shown in FIG. 11A, but the bandwidth at the time of horizontal edge detection described later is shown in FIG. As a result, the filter means 50 consisting of the LPF 51 and the HPF 52 has the characteristic that the center frequency and the bandwidth are variable.
Further, in the feedback loop 24, as described above, the phase adjusting means 2
8 and the first control means 25 are provided, and the feedback loop 24 'has an edge detection means 26 and a second control means 2
7 is provided. The edge detecting means 26 comprises a luminance signal passing filter 53, a positive edge detecting circuit 55, and a negative edge detecting circuit 56, and the second control means 27 has an OR circuit 66.
It comprises a 1H delay circuit 60.

The operation of the embodiment shown in FIG. 8 will be described with reference to FIG. FIG. 12A is a display example of an image in which the brightness changes sharply in the horizontal direction, such as “black → white → black”. The portion where the brightness changes sharply is called the horizontal edge portion. FIG. 12B shows the N-th line of FIG. 12A and the lines before and after it (N
−1 line, N + 1 line). Horizontal edge portions occur at t ₀ and t ₁ in the figure.
In satellite broadcasting, a signal obtained by emphasizing a video signal is transmitted as a modulation signal. Therefore, the modulation signal (also the demodulation signal) at the horizontal edge portion of FIG. 12B is emphasized in a high frequency range as shown in FIG. 12C. The waveform will be When it is assumed that the signal of FIG. 12C is ideally used for controlling the tracking filter, the feedback loop delay occurs when the FM demodulated signal 10 is fed back to control the tracking filter. As shown in FIG. 12C, a delay of T is generated, and the CN ratio is lowered in a portion where high frequency energy is high such as a horizontal edge portion.
Therefore, in the embodiment of FIG. 8, at a position where a horizontal edge is predicted to exist, the cutoff frequency of the tracking LPF 51 is increased and the cutoff frequency of the tracking HPF 52 is decreased, so that the Carson law bandwidth is comprehensively obtained. As shown in FIG. 12 (i), the tracking signal 64 to which the positive pulse is added as the passband control signal and the tracking signal 65 to which the negative pulse is added are
Pulses are added as shown in FIG. That is, when the voltage of the tracking signal 64 to which the positive pulse is added becomes V ₁ due to the pulse, and the tracking signal 65 to which the negative pulse is added becomes V ₀ due to the pulse, the total frequency characteristics of the tracking LPF 51 and the tracking HPF 52. Has a Carson's law bandwidth centered on the second intermediate frequency, and the CN ratio does not decrease.

The 1H delayed edge pulse signal 61, which is the predicted signal of the horizontal edge, is obtained by utilizing the vertical correlation of the video signal. That is, the luminance signal pass filter 53 causes F
Only the luminance signal 54 in the M demodulated signal 10 is extracted, the positive edge detection circuit 55 and the negative edge detection circuit 56 detect the luminance signal 54, and the positive edge pulse signal 57 and the negative edge are shaped into an appropriate pulse width. The pulse signal 58 is given to the OR circuit 66 to obtain the edge pulse signal 59 which is each addition signal, and the delay circuit 60 delays this for 1H (H: horizontal period ≈ 63.5 μsec) to obtain a 1H delayed edge pulse signal. can get. This state is shown in FIGS. Here, the luminance signal 32 and the luminance signal 54 are not treated as the same signal, because the luminance signal 32 is used as a tracking signal, the color signal trap filter 31 is used because it is necessary to minimize the delay amount by the circuit. On the other hand, since the luminance signal 54 is required to have accuracy rather than delay time, the luminance signal 54 is described separately. Therefore, the luminance signal passing filter 53 is preferably a line comb filter or the like. The positive pulse adding circuit 62 and the negative pulse adding circuit 63 add a positive pulse and a negative pulse to the phase-adjusted tracking signal 41 according to the 1H delayed edge pulse 61, respectively.

[0034]

As described above, according to the present invention, in the system for extending the threshold by using the narrow band tracking filter or the center frequency and the band width variable filter means in the video signal receiving apparatus, the feedback loop delay Therefore, it is possible to extend the threshold even in the case of a high-saturation signal for which the threshold extension effect cannot be expected, and to enhance the overall threshold extension effect. It is also possible to prevent a decrease in C / N in the FM signal of the high frequency luminance signal component.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the embodiment of FIG.

FIG. 3 is a block diagram showing a configuration example of a conventional satellite broadcast tuner.

FIG. 4 is a block diagram showing a configuration example of a conventional satellite broadcast tuner using a tracking filter system.

FIG. 5 is an explanatory diagram of pass bands of an ordinary filter and a tracking filter.

FIG. 6 is an emphasis characteristic diagram of a video signal.

FIG. 7 is a diagram showing an example of a waveform obtained by applying emphasis to a video signal.

FIG. 8 is a block diagram showing another embodiment of the present invention.

FIG. 9 is an operating characteristic diagram of a tracking filter.

FIG. 10 is a frequency characteristic diagram of a tracking LPF and a tracking HPF.

11 is an operating characteristic diagram of the filter means 50. FIG.

FIG. 12 is an operation explanatory diagram of the embodiment in FIG.

[Explanation of symbols]

 5 Second intermediate frequency signal 9 FM demodulation circuit 10 FM demodulation signal 21 Tracking filter 22 Amplification circuit 24 Feedback loop 24 'Feedback loop 31 Color signal trap filter 32 Luminance signal 35 Color signal BPF 36 Color subcarrier signal 37 Phase shift circuit 38 Phase Adjusted color subcarrier signal 40 Adder circuit 41 Phase adjusted tracking signal 50 Band pass filter means 53 Luminance signal pass filter 54 Luminance signal 55 Positive edge detection circuit 56 Negative edge detection circuit 60 Delay circuit 61 1H delayed edge pulse signal

Claims (6)

[Claims] 1. A tracking filter to which a received signal converted into an intermediate frequency component is input, and F of the received signal.
A loop for returning a tracking signal according to the M demodulated signal to the tracking filter, and a video signal receiving device for controlling the center frequency in the signal pass band of the tracking filter by the tracking signal, in the feedback loop, A video signal receiving apparatus comprising a phase adjusting means for adjusting the phase of a color subcarrier component in the FM demodulated signal. 2. The phase adjusting means includes a color signal trap filter to which the FM demodulated signal is applied, a color signal bandpass filter, and a phase shift circuit for adjusting the phase of a color subcarrier signal from the color signal bandpass filter. 2. The video signal receiving apparatus according to claim 1, further comprising: an addition circuit that adds the luminance signal from the color signal trap filter and the phase-adjusted color subcarrier signal from the phase shift circuit. 3. A band pass filter means having a variable center frequency and a pass band width to which a received signal converted into an intermediate frequency component is input, and a pass band width control signal according to an FM demodulated signal of the received signal. A loop for returning to the band pass filter means, in the feedback loop, an edge detecting means for detecting a horizontal edge from the FM demodulated signal, and the pass band width control signal based on the horizontal edge detecting signal from the means. And a control means for controlling so as to widen the pass band width of the band pass filter means, and a video signal receiving apparatus. 4. The horizontal edge detecting means includes a luminance signal passing filter to which an FM demodulated signal is input, and a positive edge detecting circuit and a negative edge detecting circuit to which the luminance signal from the filter is input, The control means adds a positive and negative edge pulse signal from the positive and negative edge detection circuit to obtain an edge pulse signal, and a delay circuit which outputs a 1H delayed edge pulse signal from the edge pulse signal,
The video signal receiving device according to claim 3, further comprising: 5. A band pass filter means having a variable center frequency and a pass band width of the received signal converted into the intermediate frequency component, and a tracking signal and a pass band width control signal according to the FM demodulated signal of the received signal. Phase adjusting means for adjusting the phase of the color subcarrier component in the FM demodulated signal in the first feedback loop, and first and second loops for returning to the bandpass filter means, First tracking means for outputting the tracking signal from the output and controlling the center frequency in the signal pass band of the band pass filter means by the tracking signal is provided, and a horizontal edge is generated from the FM demodulation signal in the second feedback loop. And a passband control means for outputting the passband control signal based on a horizontal edge detection signal from the means, Second control to increase bandwidth
And a control means of the video signal receiving device. 6. The band pass filter comprises a tracking low pass filter and a tracking high pass filter, and is configured to control the pass band of each of the filters based on the pass band width control signal and the tracking signal from the phase adjusting means. The video signal receiving device according to claim 5, wherein