JPH0480593B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a high-definition television receiver, and particularly to a high-definition television receiver suitable for receiving a high-definition television signal superimposed with a low-frequency signal for energy diffusion. Regarding machines.

[Background of the invention]

MUSE (Multiple Sub-Nyquist
A sampling encoding system has been proposed (Reference: Ninomiya et al. 2, "Satellite one-channel transmission system for high-definition television (MUSE)", Television Society Technical Report TEBS95-2).

However, this 12GHz band satellite broadcasting requires energy dispersion (References: "Broadcasting Satellite Technology" edited by Japan Broadcasting Corporation, published by Japan Broadcasting Publishing Association,
P46.), a triangular wave spread signal synchronized with the frame period is superimposed. In the conventional NTSC system, this spread signal can be removed relatively easily by clamping the horizontal blanking period. However,
MUSE is a straight TCI (Time Compressed
A signal format called "integration" that time-division multiplexes luminance signals and color difference signals is used. This multiplexes time-base compressed color difference signals line-sequentially during the horizontal retrace period. Therefore, the conventional
Unlike NTSC, there is only a flat area with no signal for four samples (one sample interval is about 60 nS, so about 0.24 μS), as shown in Figure 1. Therefore, it is difficult to perform clamping during this period due to waveform distortion and noise caused by cable mismatch.

[Purpose of the invention]

An object of the present invention is to provide a high-definition television receiver that correctly reproduces a reference DC level by removing the energy diffusion signal from a high-definition television signal on which the energy diffusion signal is superimposed without using horizontal period information, thereby obtaining a good image. Our goal is to provide the following.

[Summary of the invention]

To achieve the above objective, we use the fact that a reference voltage (for example, a half gray level indicating the zero level of a color difference signal) is inserted in the vertical retrace period, and use the DC voltage of this reference voltage between fields (or frames). By calculating the difference digitally and digitally generating a staircase wave whose time in the flat part changes according to this voltage difference, the diffused signal can be canceled with high precision without using horizontal period information. It is something.

[Embodiments of the invention]

A second embodiment of the high-definition television receiver of the present invention will be described below.
In FIG. 2 shown in the figure, 1 is the first input terminal;
2 is a second input terminal, 3 is a third input terminal, 4 is a fourth input terminal, 5 is a first AD converter, 6 is a first gate circuit, 7 is a first integration circuit, 8 is the first
9 is a second integration circuit, 10 is a third integration circuit, 11 is a first subtraction circuit, 12 is a first programmable counter, 13 is an up-down counter, 14 is a second programmable counter,
15 is a second gate circuit, 16 is a second subtraction circuit, and 17 is an output terminal.

A high-definition television signal that has been FM demodulated into a baseband signal is input from a first input terminal 1 . A spread signal is superimposed on this signal. This spread signal is, for example, a triangular wave with two repeated frames (therefore, approximately 15 Hz) as shown in FIG.
Satellite broadcasting in the 12 GHz band requires energy dispersion of 600 KHz p-p. In order to satisfy the Komai-Carson law and transmit data without difficulty, the frequency deviation of the main carrier wave should be about 10 MHzP-P. Since pre-emphasis is applied to the video signal, the low frequency spread signal is attenuated by 10dB. Therefore,
In order to spread 600 kHz P-P, it is necessary to superimpose a spread signal of about 0.2 VP-P on the video signal 1 VP-P.

By the way, MUSE is a highly band-compressed signal that requires digital signal processing on the receiving side to return to the original high-definition television signal. For this reason, the first
The input terminal is sampled and quantized by the AD converter 5. The sampling frequency of this first AD converter 5 is
MUSE sample point repetition frequency (16.2MHz)
All you have to do is choose. Further, the number of quantization bits may be 8 bits. As the dynamic range of the input section of the first AD converter 5, it is sufficient to set the video signal amplitude to 1 Vp-p, the spread signal to 0.2 Vp-p, and 1.4 Vp-p in consideration of amplitude variations. At this time, the ratio of the spread signal to the dynamic range is approximately 14%.
This occupies approximately 36 steps out of 256 steps.

The output of this first AD converter 5 is supplied to a first gate circuit 6. Here, the frame pulse separated from the input signal, the gate pulse input from the second input terminal 2 for gating the reference voltage period created using the horizontal synchronization signal,
Digital values for the reference voltage period are sampled. The extracted digital values of the reference voltage period are added and averaged for each reference voltage period by the first integrating circuit 7.

A frame pulse separated from the input signal is input from the third input terminal 3, and the average value of the reference voltage period near the rising start and the average value of the reference voltage period near the falling start of the spread signal shown in FIG. The values are separated by the first switch 8 and output to two outputs respectively.

These two average values are separately added and averaged over a plurality of frames by the second integration circuit 9 and the third integration circuit 10, respectively. In this way, the minimum and maximum values of the spread signal shown in FIG. 3 can be detected digitally and accurately. The difference between the second integration circuit 9 and the third integration circuit 10 is calculated by the first subtraction circuit 1.
1 and find the amplitude of the spread signal. Assuming that this amplitude is equal to N steps, the counter value of the up-down counter 13 is changed by N steps during one frame to obtain a staircase wave for correction.
At this time, the frame in which the counter value is to be increased or decreased can be easily determined based on the sign of the output of the first subtraction circuit 11.

Further, the number of steps in one frame of the up-down counter 13 can be changed as follows.

If the number of steps determined by the first subtraction circuit 11 is N, the number of scanning lines of a high-definition television signal is 1125, so the length L per step is L=(1125÷N)×H (S) (However, H: 1 horizontal scanning period is approximately 29.7 μS). An example of the relationship between the number of steps and the length per step is shown in FIG. For example, when the number of steps is 36, the length of one step is approximately 31.3H.
Therefore, the first programmable counter 12
The frequency division number of the second programmable counter 14 is set to 31, and the frequency division number of the second programmable counter 14 is set to 3. A signal of the same frequency is pulse gated by the second programmable counter once every three pulses of the output of the first programmable counter 12. In this way, the first programmable counter will perform frequency division by 31 twice out of three times and once by 32. Therefore, on average 31.3
This means that a frequency division operation has been performed, and the length per step can be set to 31.3H. In this way, by gating the input signal of the first programmable counter with the output of the second programmable counter that divides the output of the first programmable counter, it is possible to process fractions. Of course, if the accuracy is sacrificed a little, the second programmable counter 14 and the second gate 15
There is no harm in deleting it.

In this way, in order to correct the triangular wave-like diffused signal, the digitally generated step-wave signal is converted into the first signal.
A second subtraction circuit 16 from the output signal of the AD converter 5
subtract digitally. In this way, the correction residual can be kept within 1 bit width, so it can be set to a value of -46 dB or less. Since the detection limit for flicker is about -40 dB, it is possible to set it to a value that is completely acceptable.

In the above explanation, the video signal is AD-converted in a form in which the spread signal is superimposed, but in this form, the quantization accuracy deteriorates by the amplitude of the spread signal. By adding an AD converter or DA converter that operates at low speed, it is possible to prevent this deterioration of quantization accuracy. An example in this case is shown in FIG. In Figure 5,
18 is LPF, 19 is second AD converter, 20 is
DA converter, 21 is the third subtraction circuit, 22 is the second
23 is the fourth integration circuit, 24 is the fifth
, and 25 is a fourth subtraction circuit.

The input signal input from the first input terminal 1 is
After removing high frequency noise with LPF18, the second
The AD converter 19 samples and quantizes the reference voltage within the vertical retrace period. The number of bits of this second AD converter 19 should be 6 bits, and the operating speed should be about a fraction of one horizontal scanning period, that is, a conversion speed of about 100 KHz. The following process is the second
In the same way as in the figure, up-down counter 1
3 operations are controlled. In the case of FIG. 5, the output of this up-down counter 13 is converted into an analog signal by a DA converter 20. This converted analog signal is subtracted from the input signal by a third subtraction circuit 21. In this way, the correction waveform is generated purely digitally, but the subtraction process is performed analogously. The number of bits of this DA converter 20 may be 6 bits, and the operating speed may be about 10 KHz.

In this way, since the spread signal is corrected as an analog signal, the input dynamic range of the first AD converter 5 used for signal processing can be used only for the video signal. At this time,
The conversion sensitivity of the DA converter 20 varies due to the influence of circuit elements, and there is a possibility that a very small error may occur in the amplitude of the correction waveform. In order to completely correct this, the frame-to-frame level difference of the reference voltage during this vertical retrace period, that is, the correction error, is determined from the output of the first AD converter 5 using the same procedure, and this correction error is eliminated. All you have to do is control the conversion sensitivity of the DA converter. At this time, the first
If the switch 8 and the second switch 22 are controlled in synchronization including their polarities, the first subtraction circuit 11
According to the sign of , it is possible to correctly control whether the conversion sensitivity of the DA converter 20 is increased or decreased depending on the sign of the fourth subtraction circuit 25 .
Of course, the removal of the spread signal does not have to be perfect;
This feedback control of the conversion sensitivity of the DA converter 20 is not necessarily required, as it is sufficient that it is -40 dB or less for a video signal of 1 Vp-p.

Furthermore, the AD converter 19 has the same level as the second AD converter 19.
Providing a converter to perform correction error detection and making it independent from signal processing for returning the compressed band signal to the original high-definition television signal can also be said to be an effective means for simplifying the device.

〔Effect of the invention〕

As explained above, since the high-definition television receiver according to the present invention digitally generates a correction waveform for correcting the energy diffusion signal, it is possible to accurately and stably correct the energy diffusion signal, thereby producing a high-quality video signal. This makes it suitable for use as a 12GHz band satellite broadcasting receiver.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the waveform of the horizontal synchronization period of MUSE, FIG. 2 is a diagram showing an embodiment of the high-definition television receiver of the present invention, FIG. 3 is a diagram showing an example of the energy diffusion signal waveform, and FIG. This figure is a diagram showing the relationship between the number of steps of a staircase wave and the length per step, and FIG. 5 is a diagram showing a second embodiment of the high-definition television receiver of the present invention. 1, 2, 3, 4... Input terminal, 5, 19...
AD converter, 6, 15...gate circuit, 7, 9,
10,23,24...Integrator circuit, 8,22...Switch circuit, 11,16,21,25...Subtraction circuit, 12,14...Programmable counter, 1
3...Up-down counter, 20...DA converter.

Claims (1)

[Claims] 1. In a high-definition television receiver that receives a high-definition television signal on which a triangular wave for energy diffusion is superimposed, the reference voltage period inserted in the vertical blanking period of the high-definition television signal, which is the input signal, is sampled and quantized. AD converters 5 and 19 that detect the output of the AD converter, two integrators 9 and 10 that integrate the voltages of the different reference voltage periods detected from the output of the AD converter for a plurality of periods, and calculate the difference between the integrator outputs. A difference circuit 11, and counting circuits 12, 13, 1 whose counting speed of the counted value is modulated by the output of the difference circuit.
4 and 15, and subtraction circuits 16 and 21 for subtracting the output of the counting circuit from the input signal, and extracting a high-quality television signal from which the triangular wave for energy diffusion has been removed as the output of the subtraction circuit. A high-definition television receiver.