JPH0723256A - Waveform equalizer - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a waveform equalizer for correcting distortion of a television signal, and provides a waveform equalizer which can be commonly used for both a MUSE signal and an NTSC signal. A distortion detecting reference signal is taken from a television signal corrected by a waveform equalizing digital filter (12) into a waveform memory (6), and a signal switching circuit (8) is provided.
Then, the signal that has been subjected to the difference processing by the difference circuit (7) and the signal that has not been subjected to the difference processing are switched by the MUSE / NTSC discrimination signal and guided to the distortion detection circuit (10). The tap coefficient of the digital filter (12) is modified. [Effect] With the above configuration, by switching the detection operation of the reference signal between the MUSE signal and the NTSC signal, the waveform equalization processing can be performed regardless of the difference in the reference signal waveform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and more particularly to a waveform equalizer for correcting waveform distortion such as ringing and ghost caused by distortion of a transmission line.

[0002]

2. Description of the Related Art In transmitting a television signal, there is a problem that a received image is deteriorated due to distortion in a transmission line. High definition signal transmission method MUSE
In the method, analog sample value transmission is performed,
If the transmission line is distorted, ringing interference due to interference between sampled values occurs and image quality is degraded. As a means for solving this, for example, IEICE Technical Report Vol. 88, No. 300
(1988) The waveform equalizing circuits described in the first to seventh terms are generally known. According to this, the sample value transmitted at the transmission rate of 16.2 MHz is 16.2.
The main line signal resampled at MHz and digitized, and in parallel with this, double the sampling frequency of 3
A transversal filter for equalization that creates correction data in which the sampling phase matches the main line system from the digital signal resampled at 2.4 MHz is provided, and the correction value obtained from this transversal filter is delayed to the main line signal. Add the amounts together. At this time, VITS
(Vertical Interval Test S
signal) is used to obtain the tap coefficient of the transversal filter, and the tap coefficient is corrected so that the error between the detected VITS waveform and the ideal impulse response waveform is minimized, thereby performing waveform equalization processing.

On the other hand, the current NTSC television signal has a problem of ghost interference as distortion during transmission. A waveform equalizing circuit for removing the ghost is described in, for example, Technical Report Vol. 1
3, No. 32 (1989), items 31 to 36 are known. According to this, the transmitted NTSC signal is converted into a digital sample value by an A / D converter, the sample value is input to a transversal filter, and GCR (Ghost Cancello
r Reference) signal by detecting
Ghost correction is realized by correcting the tap coefficient so that the detection error of the output of the transversal filter is minimized.

[0004]

In a television receiver capable of receiving a MUSE type television signal and an NTSC type television signal, the MUSE waveform equalizing circuit and the NTSC waveform equalizing circuit are provided in different systems. Therefore, a plurality of transversal filters having a large circuit scale are used, and it is desirable to share the waveform equalization circuit in order to reduce the circuit scale. However, since the MUSE signal and the NTSC signal have different sampling frequencies, and the format and timing of the reference signal for detecting the distortion in the transmission path are different, it is difficult to share the detection circuit. For example, with the MUSE signal, 1125
The sinX / X pulse waveform is inserted as VITS on the first and second lines in the line, and the distortion component is detected by comparing this VITS waveform with the ideal impulse response waveform, and the tap coefficient of the transversal filter is calculated. To do. On the other hand, in the NTSC signal, the sin X / X bar waveform is inserted as the GCR signal in the form of circulating in 8 fields on the 18th line and the 281st line of the 525 line, and by performing the 8 field sequence processing and the difference processing. , Sin X / X pulse impulse response waveforms are obtained. In this way, MUSE signal and NTSC
In terms of signals, there are differences in the detection method of the reference signal and the sampling frequency, making it difficult to apply the same waveform equalization circuit to both.

[0005]

In order to solve the above problems, an A / D converter for converting a television signal into a digital sample value, a transversal filter in which tap coefficients can be adaptively changed, A reference signal waveform acquisition memory, a difference circuit for obtaining an impulse response as a difference between GCR signals, and a signal switching means for selecting either the reference signal from the difference circuit or the reference signal as it is without obtaining a difference. It is realized by including distortion detection means for detecting transmission path distortion from a reference signal and coefficient setting means for calculating and setting tap coefficients of the equalization transversal filter.

[0006]

According to the above construction, when the waveform equalization processing of the MUSE signal is performed when the reference signal for detecting the transmission line distortion is taken in, the signal switching means is provided for detecting the transmission line distortion. A signal that does not pass through the differential circuit is selected as the reference signal, and the VITS pulse is supplied to the distortion detecting means. On the other hand, when performing the waveform equalization processing of the NTSC signal, the signal switching means selects the reference signal output from the differential circuit, and the differential circuit performs differential processing on the sinX / X bar signal to generate an impulse response waveform. , Used for distortion detection. As a result, even the NTSC signal is MUS
Distortion can be detected by the same algorithm as the distortion detection of the E signal, and the circuit can be shared.

[0007]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a diagram showing an embodiment of the present invention.
In FIG. 1, 1 is an input terminal for incoming television signals,
Reference numeral 2 is an A / D converter for sampling an analog television signal and converting it into a digital television signal.
Is a transversal filter for generating correction data for equalization, 4 is a delay circuit for adjusting the delay amount of the main line signal to the delay amount in the correction signal equalization transversal filter 3, and 5 is a main line signal. An adder circuit for adding the correction data to, a waveform memory for taking in a reference signal for detecting the distortion of the transmission line, and a sinX /
A differential circuit that obtains a sinX / X pulse waveform from the X-bar waveform, 8 is a signal switching circuit that selects either the signal guided from the waveform memory or the signal guided from the differential circuit, and 9 controls the acquisition timing of the waveform memory. A timing control circuit, 10 is a distortion detection circuit that detects a distortion component from a reference signal loaded in a waveform memory, 11 is a coefficient setting circuit that sets a tap coefficient of a transversal filter, and 12 surrounded by a broken line is a waveform equalization transformer. A versal filter, 13 is an output terminal for guiding a television signal after waveform equalization to a signal processing circuit at a subsequent stage, and 14 is an input terminal for a discrimination signal of a MUSE signal and an NTSC signal.

The operation of this embodiment will be described. First, the television signal guided to the input terminal 1 is converted into a digital television signal by the A / D converter 2. At this time, when the incoming signal is a MUSE signal, the A / D converter 2 has, for example, a MUSE sampling frequency of 16.
22.4 MHz or 22.4 times oversampling
A clock signal of MHz is supplied, and in the case of an NTSC signal, for example, four times the subcarrier frequency is about 14.3 MH.
A z clock signal is provided and sampled into signals of respective data rates. The television signal after A / D conversion is guided to a waveform equalization transversal filter 12 including a main line delay circuit 4 and a correction signal generation transversal filter 3. The correction signal generating transversal filter 3 generates a correction signal for correcting the distortion component, and the delay circuit 4 delays the main line signal and the correction signal to be equal to the delay amount in the transversal filter 3. The addition is performed by the adder 5 to correct the transmission line distortion. The corrected television signal is guided from the output terminal 13 of the waveform equalization circuit to the signal processing circuit in the subsequent stage, and the waveform memory 6 for taking in the reference signal is also provided.
Is supplied to. In the waveform memory 6, the timing control circuit 9
The line on which the reference signal waveform is superimposed is selected and fetched in accordance with the type of the incoming signal by the control signal from. Timing control circuit 9 uses MUSE / NTSC
The control signal of the memory is switched according to the determination signal, for example,
When the MUSE signal arrives, the VITS pulse on the first and second lines is detected for each frame and is stored in the waveform memory 6. When the NTSC signal arrives, the GCR signals on the 18th and 281th lines are fetched into the waveform memory 6, and the sequence processing is performed on the data of 8 fields.
Take out the bar waveform. The signal switching circuit 10 is MUSE
In the case of the MUSE signal, which is switched by the / NTSC discrimination signal, the reference signal taken into the waveform memory 6 is guided to the distortion detection circuit 10 through the signal switching circuit 8, and when the incoming signal is the NTSC signal, the difference circuit 7 Eg 1
Clock difference processing is performed, the sinX / X bar waveform is differentiated, and the GCR signal after being converted into an impulse response is guided to the distortion detection circuit 10. The distortion detection circuit 10 compares the ideal impulse response waveform stored inside and the captured impulse response waveform to detect transmission path distortion. At this time, since the ideal transmission path characteristics are different between the MUSE signal and the NTSC signal and the impulse response also changes, the ideal impulse response waveform of the reference is switched by the MUSE / NTSC discrimination signal,
Both distortion detections are possible. In the coefficient setting circuit 11,
Transversal filter 3 for correcting distortion components
The tap coefficient of is calculated and the coefficient value is transferred to the transversal filter 3. The transversal filter 3 is set so that the transmission line distortion detected by the distortion detection circuit 10 approaches zero.
The coefficient value of is repeatedly corrected and waveform equalization processing is performed.

As described above, according to this embodiment, M
The reference signals of the USE signal and the NTSC signal can both be treated as the same impulse response, and it is possible to share the distortion detection or the distortion correction coefficient calculation.

Further, in the present embodiment, the difference detection circuit 6
Although the one clock difference is detected, the same effect can be obtained not only with the one clock difference but also with the two clock difference.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, reference numeral 15 is a microprocessor, the other components are the same as those in FIG. 1, and the timing control, distortion detection, coefficient setting processing and the like in FIG. 1 are replaced with one microprocessor. With such a configuration, even when the distortion detection process and the coefficient calculation process are processed by software, it is easy to share the software process, and it is possible to easily switch the process between MUSE and NTSC.

Next, a third embodiment of the present invention will be described with reference to FIG. 3, each component is shown in FIG.
Similar to FIG. 2, the insertion portion of the difference circuit 7 and the signal switching circuit 8 is in the preceding stage of the waveform memory 6. In this case, when the MUSE signal arrives, the switching circuit 8
The incoming reference signal is taken into the waveform memory 6 as it is, and the same processing as that of the waveform equalizing circuit of the normal MUSE signal is performed. When the NTSC signal arrives, the switching circuit 8 is switched to the signal guided from the differential circuit 7, The obtained signal is taken into the waveform memory 6. Even with such a configuration, the same effect as that of the embodiment of FIG. 1 can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the embodiment of FIG. 4, the basic configuration is the same as that of FIG. 1 and FIG. 2, but the MUSE / NTSC discrimination signal is guided to the transversal filter 3 and the delay circuit 4, and the configuration of the transversal filter 3 can be switched. The delay circuit 4 is configured as a variable delay line so that the delay amount can be switched. In the present embodiment, as the configuration of the transversal filter 3, the number of filter taps that determines the correctable range is set to different values for the MUSE signal and the NTSC signal. Generally, the MUSE signal is subjected to waveform equalization for the purpose of removing a nearby interference such as ringing, and the compensable range may be relatively small. However, in the case of the NTSC signal, even a ghost disturbance with a large delay time is possible. It is desirable that the number of filter taps is large so as to be compatible. As described above, when the MUSE signal and the NTSC signal have different transversal filter configurations, the delay amount of the correction signal is different. Therefore, the delay circuit 4 determines the delay amount of the main line signal by the MUSE / NTSC determination signal. The timing in the adder 5 is matched by switching.

As described above, according to this embodiment, the MUSE
Even when the signal and the NTSC signal have different transversal filter configurations, the waveform equalization circuit can be shared as in the first embodiment.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, each component and basic operation are the same as those of the other embodiments described above. As a feature of this embodiment, the difference circuit 7 and the signal switching circuit 8 are realized by the processing by hardware in the other embodiments, but the portion corresponding to the difference circuit 7 and the signal switching circuit 8 is the microprocessor 15. Waveform memory 6
The reference signal taken in is directly led to the microprocessor 15. According to the configuration of the present embodiment, the processing time of the difference processing and the like becomes slower than that of the method using hardware, but the MUSE processing and the NTSC processing can be easily switched, and the waveform equalization circuit can be easily shared.

Although not particularly described in the above-described embodiments of the present invention, the transversal filter 12 for waveform equalization includes a correction signal generating transformer as in the first to fifth embodiments. The configuration is not limited to the combination of the Versal filter 3 and the main line delay circuit 4, and a filter of other configuration such as a transversal filter for directly filtering the main line signal may be used.

[0018]

According to the present invention, the MUSE signal and the NTS signal
Regardless of the difference in the format and timing of the reference signal waveform of the C signal, the transmission line distortion can be detected, the waveform equalization processing for both signals can be performed by the same circuit, and a separate waveform equalization circuit is required. Therefore, it is possible to reduce the circuit scale and improve the image quality in a television receiver.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Television signal input terminal, 2 ... A / D converter, 3 ... Correction data generation transversal filter, 4 ... Main line signal delay circuit, 5 ... Adder, 6 ... Reference signal waveform acquisition memory, 7 ... Difference circuit, 8 ... Signal switching circuit, 9 ... Waveform memory capture timing control circuit, 10 ... Distortion detection circuit, 11 ... Tap coefficient setting circuit, 12 ... Digital filter for waveform equalization, 13 ... Output terminal of waveform equalization circuit, 14 ... MUSE / NTSC discrimination signal input terminal, 15 ... Microprocessor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuo Nagata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stocks, Hitachi Media Visual Media Research Institute (72) Inventor Hatsuji Kimura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi Media Co., Ltd. Media Research Institute (72) Inventor Takumi Okamura 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Hitachi Media Media Research Center

Claims (2)

[Claims] 1. A television receiver capable of receiving MUSE and NTSC television signals, comprising:
In a waveform equalization circuit for correcting transmission path distortion of a television signal, an A / D converter for converting an analog television signal into a digital sample value sequence, a digital filter for correcting the distortion of the television signal, and a television Waveform memory that takes in the distortion detection reference signal from the John signal, and distortion detection means that detects the distortion component from the reference signal,
Coefficient setting means for controlling the coefficient of the digital filter according to the distortion, difference processing means for extracting the difference of one sample or two samples in the time direction of the reference signal, and signal switching for switching the signal guided to the distortion detecting means. The signal switching means selects a reference signal from the waveform memory that has not been subjected to difference processing by the difference processing means when the MUSE signal is received, and the difference processing means selects the reference signal when the NTSC signal is received. A waveform equalizing device characterized in that a processed reference signal is switched by a discrimination signal so as to be selected, and distortion is detected from the reference signal guided to the subsequent stage of the signal switching means by using the distortion detecting means. . 2. The waveform equalizer according to claim 1, wherein the waveform memory is arranged at a stage subsequent to the signal switching means, and when the MUSE signal is received, the reference signal which is not subjected to the differential processing from the digital filter. Select, NTSC
A waveform equalization device, characterized in that, when a signal is received, the reference signal subjected to the difference processing by the difference processing means is selected and stored in the waveform memory.