JPS61261993A - Receiver - Google Patents

Abstract

PURPOSE:To always detect a good frame synchronization by not performing diffusion elimination when a synchronization against a receiving signal is not obtained. CONSTITUTION:A generating circuit 3 which generates the elimination signal of a diffusion signal and a constant voltage circuit 11 which generates voltage equal to the synchronizing period of the elimination signal are provided. And a switch 12 is switched according to a synchronizing state against the receiving signal. In other words, when the synchronization against the receiving signal is not obtained, the voltage from the constant voltage circuit 11 is added to the receiving signal at an adder 2. On the other hand, when the synchronization is obtained, the elimination signal from the generating circuit 3 is added to the receiving signal.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Industrial field of application B. Outline of the invention C. Prior art (Figs. 2 to 5) D. Problem to be solved by the invention E. Means for solving the problem (Fig. 1) F. Effect G. Implementation Example (FIG. 1) H Effects of the Invention A Industrial Application Field The present invention relates to a receiving device that receives a broadcast signal containing a spread signal.

B. Summary of the Invention The present invention relates to a receiving device that receives a broadcast signal containing a spread signal, and is capable of obtaining good and quick synchronization by cutting off the spread signal removal signal when the reception is asynchronous. It is.

C. Conventional technology MtlS is a new transmission method for so-called Western quality television.
E(Multiple 5ub-Nyquist Sa
mpling encoding) method has been proposed (Presentation commemorative lecture, 1-New transmission method for disordered crystal television (MUSE) J, Tasuku Ninomiya-1 June 6, 1982
Japan, NHK Research Institute of Technology/Basic Broadcasting Science Research Institute).

That is, in this method, the transmitting side transmits the luminance signal Y and the color difference 4'i1 CM- as shown in FIGS.
If there is CI, /, the color difference signal CN-Cl of these
4I is compressed on the time axis to 1/4 and inserted into the horizontal blanking period at the leading end of each corresponding luminance signal Y in line order to form a TCI signal as shown in the figure. This TC
The I signal is sampled at 64.8 MHz as shown in E of the same figure, and one sample is extracted from every 4 samples of this sampling data, and as shown in F of the same figure, the sub signal is dot-interleaved with each other and goes around in 4 fields. Form a Nyquist sampling signal. Therefore, the frequency of sub-Nyquist sampling becomes 16.2 MHz, and thereby the baseband signal bandwidth, which was originally 20 MIIz, can be compressed to 8.1 MIIz. This signal is frequency-modified (FM) and transmitted via a broadcasting satellite or the like.

On the other hand, on the receiving side, the received signal is demodulated and the above-mentioned 8.1 M
A sub-Nyquist sampling signal of llz is extracted.

This signal is sampled at 16.2 MHz, this sampling data is written to the memory as shown in the above figure, and these data and the data at the non-sampling points indicated by blanks are converted as shown in figure G. - Interpolate to restore the TCI signal as shown in D in the above figure. From this signal, a luminance signal Y and color difference signals CM and CM as shown in A to C in the above-mentioned diagram can be extracted.

.

In this way, it becomes possible to transmit a crystal quality television signal using the MUSE'7i method, for example, by one channel of satellite broadcasting with a bandwidth of 27 MHz.

By the way, in the above-mentioned satellite broadcast transmission, in order to prevent interference with existing terrestrial microwave lines, etc., it is considered that a so-called spread signal is superimposed and transmitted. In this case, the spread signal in the above-mentioned MLISE method is at a predetermined level during the horizontal synchronization signal HD period, rises during the subsequent color difference signal C period, and further falls during the luminance signal Y period, as shown in FIG. A waveform that is completed in one horizontal period is used, and this spread signal is added to the converted MUSE signal, which is then modulated and transmitted.

Therefore, when receiving such a signal, it is necessary to remove the above-mentioned spread Ig signal and then perform inverse conversion of the MUSE method.For this reason, conventional equipment such as the one shown in Fig. 4 has been used. It had been proposed.

In the figure, the above-mentioned received and demodulated Muse system signal is supplied to the input terminal <11. This signal is sent to the adder (
2), and a cancellation signal of opposite polarity to the above-mentioned spread signal from the spread cancellation signal generation circuit (3) is added to remove the spread signal.

Furthermore, this signal is supplied to a clamp circuit (4) and clamped to a predetermined level, and this clamped signal is
The signal is supplied to a conversion circuit (5) and digitally converted into, for example, 8 bits, and then taken out to an output terminal (6) and supplied to a MUSF such as a subsequent memory and a system inverse conversion circuit (not shown). Further, the digitally converted signal is supplied to a synchronization detection circuit (7), and the detected synchronization signal is supplied to a basic clock generation circuit (8) to form a basic clock signal. Further, an internal horizontal synchronizing signal formed from this basic clock is supplied to a spreading removal signal generating circuit (3).

The naori lamp circuit (4) includes a pedestal clamp circuit (4) which normally uses a predetermined level in the horizontal synchronization signal as a reference.
1) is used, but since such ramping cannot be performed when the horizontal synchronization signal is not synchronized, an average value clamp circuit (42) is provided in parallel, and the generation circuit (42) is used.
Control indicating whether synchronization of the horizontal synchronization signal from 8) has been obtained
4) can be switched.

By the way, in the MUSH system signal, the synchronization signal is
It is inserted with the same polarity (positive polarity) as the video signal (luminance signal Y, color difference signal CM-C1, I). This is for example NT
This is to prevent the overall amplitude of the signal from expanding when a synchronizing signal of opposite polarity is used as in the SC system, and particularly from widening the band when transmitting an FM signal.

A frame synchronization signal corresponding to a vertical synchronization signal of a normal video signal is configured as follows.

That is, FIG. 5A shows a frame synchronization pattern provided, for example, at the 605th position among 1125 horizontal periods of screen quality television.

In the figure, a blank period of arbitrary length is provided consecutively to the horizontal synchronization signal HD, and after that, 17.5 pairs of pulses that are inverted between the highest and lowest levels of the signal are provided every four clock periods. . This is followed by a highest or lowest level pulse of 16 clock periods, followed by a pulse that is the inverse of the previous portion of 8 clock periods.

Immediately after the pulse of this 8-clock period, the horizontal synchronization signal HD of the next horizontal period continues. The frame synchronization signals are provided in the 605th and 606th horizontal periods inverted from each other, and the leading edge of the pulse in the 16 clock period of the frame synchronization signals is used as a reference for phase synchronization.

In order to obtain synchronization from the above signal, first detect the above frame synchronization pattern in the signal, use this detection signal to pull in synchronization within ±1 clock period, and then use horizontal synchronization signal HD to achieve phase synchronization. Make sure to apply .

By the way, when the above-mentioned spread signal is superimposed, this superimposed frame synchronization pattern becomes as shown in B of the above-mentioned figure. Therefore, the spread signal can be removed by adding a removal signal of opposite polarity to the spread signal as shown in C in the above figure to this signal.

However, in this case, normal removal can be performed after synchronization of the horizontal synchronizing signal is obtained, and before that, the removal signal from the generation circuit (3) is generated asynchronously. For this reason, for example, a removal signal that should not correspond to the color difference signal part (shown with a broken line)
may be added to the luminance signal portion, and in this case, the level change due to the spread signal will be increased.

Although the level change due to the spread signal is schematically enlarged in the figure, it is actually about several percent of the amplitude of the video signal. If the level change is only a few percent, there is no problem in detecting the frame synchronization pattern after AD converting this signal, but if this level change is doubled, for example, Since the duty of the pulse signal during that time is changed, normal detection cannot be performed. For this reason, normal synchronization detection could not be performed, and there was a risk that an extremely long time would be required to obtain synchronization.

D. Problems to be Solved by the Invention Conventional devices were constructed as described above. For this reason, when the extended signal is asynchronous, the frame synchronization pattern cannot be detected well, resulting in problems such as a large amount of time being required until synchronization is achieved.

Means for Solving the E tfJ1 Problem The present invention provides a receiving device that receives a broadcast signal containing a spread signal, including a generating circuit (3) that generates a signal for removing the spread signal, and a circuit for synchronizing the signal for removing the spread signal. a constant voltage circuit (11) that generates a voltage equal to the period; a switch (12) that switches between a removal signal from the generation circuit and a voltage from the constant voltage circuit;
It has an addition circuit (2) that adds the signal from this switch to the received signal of the broadcast signal (input terminal (1)), and switches the switch according to the state of synchronization with the received signal (control signal). When synchronization with the received signal cannot be obtained, the voltage from the constant voltage circuit is added to the received signal, and when synchronization with the received signal is obtained, the removal signal from the generation circuit is added to the received signal. This is a receiving device designed to add .

F. Effect: According to this device, since spreading cancellation is not performed when synchronization with the received signal cannot be obtained, good frame synchronization can always be detected, and this also reduces the number of times synchronization is detected. Therefore, the time required for synchronization to converge can be significantly shortened.

G. Embodiment In FIG. 1, a constant voltage circuit (11) that generates a voltage equal to the voltage in the period corresponding to the horizontal synchronization period of the removal signal is provided in parallel with the above-mentioned diffusion removal signal generation circuit (3), Voltage from this constant voltage circuit (11) and generation times II! 8
(The removal signal from 31 is switched by a switch (12) and supplied to an adder (2).
Switching 2) is performed by a control signal from the basic clock generation circuit (8), similar to the switching of the clamp circuit (4) described above. The rest is the same as the conventional device.

Therefore, according to this device, until synchronization with the received signal is obtained, a constant voltage corresponding to the synchronization period from the constant voltage circuit (11) is added to the received signal, resulting in an erroneous cancellation signal. There is no risk that the level change will be increased by Therefore, the number of times synchronization is detected is increased, and the stability of the PLL etc. of the basic clock generation circuit (8) is increased, so that the synchronization convergence time is shortened.

H Effects of the Invention According to the present invention, since υ' is made so that spreading cancellation is not performed when synchronization with the received signal cannot be obtained, it is possible to detect very good frame synchronization. Since the number of times synchronization is detected is increased, the time required for synchronization to converge can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an example of the present invention, and FIGS. 2 to 5 are diagrams for explaining conventional devices. (11 is the input terminal, (2) is the addition circuit, (3) is the diffusion removal signal generation circuit, (4) is the clamp circuit, (5) is the AD
Conversion circuit, (6) is output terminal, (7) is synchronization detection circuit,
(8) is a basic clock ordering circuit, (11) is a constant voltage circuit, and (12) is a switch. Diagram 1 of the real multicolored row

Claims (1)

[Scope of Claims] A receiving device that receives a broadcast signal containing a spread signal, comprising: a generation circuit that generates a signal for removing the spread signal; and a constant voltage circuit that generates a voltage equal to a synchronization period of the removal signal. , a switch for switching between the removal signal from the generation circuit and the voltage from the constant voltage circuit, and an addition circuit for adding the signal from the switch to the received signal of the broadcast signal, and synchronization with the received signal. When synchronization with the received signal cannot be obtained, the voltage from the constant voltage circuit is added to the received signal, and when synchronization with the received signal is obtained, the voltage from the generator circuit is added. A receiving device configured to add a removed signal of the above to the received signal.