JPS5923150B2 - High definition broadcast converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a converter for high definition broadcasting.

The current television broadcasting system is NTSClPAL. S
Although there are methods such as ECAM, the resolution cannot necessarily be said to be sufficient in any of them.

In particular, there is a demand for higher resolution for Imauta broadcasting, which requires larger screens. Therefore, it is certain that high-definition broadcasting will be implemented in the near future, with the number of scanning lines being about 2 to 3 times that of current broadcasting, and the range width being about 4 to 9 times that of current broadcasting. However, even if high-definition broadcasting begins, receivers that can receive it will not become widespread immediately, so it is necessary to prepare an adapter that can receive just the broadcast content and connect it to a current television receiver to receive it. is possible. If you do this,
Receiver power {Due to the fact that it is for semi-television broadcasting,
Although high-definition images cannot be obtained, it is possible to know the content of the broadcast. Therefore, it is an object of the present invention to enable a television receiver for standard television broadcasts to also receive high-definition broadcasts.

As an example, consider high-definition broadcasting in which the number of scanning lines is 1050, twice the current 525, and the luminance signal bandwidth is 20 MHz.

The detailed specifications are shown in the table below. Figure 1 shows the relationship between the bands shown in this table.

In order to receive such high-definition broadcasts on current color receivers, time axis expansion is required due to the scanning time.
Charge coupled devices (CCDs) and bucket brigade devices (BBDs) are convenient analog memory elements for this purpose. Recently, high-speed CCDs have been announced one after another, and some that directly store video signals, such as the one shown in FIG. 1, have already appeared in the laboratory. Therefore, it is thought that CCDs satisfying such performance will soon be available in large quantities at low cost. FIG. 2 is a block diagram showing one embodiment of the present invention. 1 is an antenna for receiving high-definition broadcasting, 2 is a tuner section, 3 is a video intermediate frequency amplification stage, 4
is a detector, 5 and 6 are analog memories such as CCD, 7
8 is an oscillation circuit, and 8 is a frequency divider circuit. The oscillation circuit 7 and the frequency divider circuit 8 provide timing for writing and reading data into and from the analog memories 5 and 6.

9 is a low-pass filter for extracting only the luminance signal; 10 is a mixing circuit; 11 is a band amplifier for extracting only the chrominance signal;
12 is a frequency conversion circuit, 13 is a pilot burst gate circuit, 14 is a phase detector, 15 is a variable oscillator that constitutes a phase lock loop together with the phase detector 14, 16 is a synchronous separation and pulse extraction circuit, and 17 is a burst gate. The circuit includes a frequency dividing circuit 18 and a phase comparator 19, which together with the oscillation circuit 7 and the frequency dividing circuit 18 form a phase locked loop.

20 is a standard television broadcast receiver having a video signal input terminal.

S1 to S4 are switches that control write and read modes of the memories 5 and 6. Next, the operation of the embodiment shown in FIG. 2 will be explained using the waveform diagram shown in FIG.

The high-definition signal input from antenna 1 is sent to tuner 2.
The signal is converted to an appropriate intermediate frequency by the intermediate frequency amplifier circuit 3 and amplified by the intermediate frequency amplification circuit 3. The amplified signal is detected by a detector 4. The frequency spectrum of this detected signal is shown in FIG. Further, the waveform shown in the time domain is shown in FIG. 3A. A chrominance signal and a luminance signal exist in a superimposed manner in the range indicated by A, S indicates a synchronization signal, P indicates a pilot burst signal, and B indicates a burst signal for color signal reproduction. The pilot burst signal P is a pilot signal for creating the color subcarrier of 3.58MHz for current color television broadcasting from 1/2 of the color subcarrier of 25.04MHz for high definition, and is (25.04/2). 13.
58 = 8.94 MHz sine wave. Now, when the switches S1 to S4 are in the positions shown in the figure (side a), high-definition video signals are supplied to the analog memory 5. From the other input to the analog memory 5, a clock pulse must be injected for shifting the analog memory quantity to the next memory element in sequence. The frequency of the clock pulse at this time is generally selected to be three times the frequency of the color subcarrier in order to completely convey the phase information of the color subcarrier frequency. Therefore, it is better to select 25.04×3-75.12 MHz. The circuit that creates this clock pulse is circuit 7.
18 and 19 are phase lock loops. The output signal from the detector 4 is guided to a synchronous separation circuit 16, where it is synchronously separated and only the synchronous signal S is taken out. Further circuit 16
The pulse is shaped using a mono-multivibrator or the like so that the pulse appears at the position of the burst signal B in FIG. The burst gate circuit 17 extracts only the burst signal B from the output signal of the detector 4 and the aforementioned pulses, and leads this output to the phase comparator 19. Oscillation circuit 7 is 75MHz
This is a variable oscillator that oscillates nearby, and the frequency divider 18 counts down this to 1/3, and leads this output to the other end of the phase comparator 19. In the phase comparator 19, these two
The signals are phase-compared and this information is guided to an oscillation circuit 7, which is a variable oscillator, to form a phase lock loop. The clock pulse output of the oscillation circuit 7 is supplied to the analog memory 5 via the a contact of the switch S2, and the signals from the detector 4 are stored one by one. At present, the capacity of the analog memories 5 and 6 is just enough to be filled in 31.75 μs for one horizontal period (hereinafter referred to as 1H period) of high-definition broadcasting, that is, 31.75 μs.
．． It is set to have only 75 μs×75.12 MHz+2385 bits. By the way, the switching timing of the switches S1 to S4 is changed for a period a as shown in Fig. 3 (c).
(Such technology is well known to those skilled in the art), this corresponds to 2H of high-definition broadcasting, so the 1H signal will be temporarily stored. 2
It is rewritten by the Hth signal, and only the 2Hth signal remains at the end of the a period, that is, at the end of the 2Hth signal.

If the switches S1 to S4 are set to be switched to the b side when the 2H-th memorization is completed (such a technique is well known to those skilled in the art), then the analog memory 6 will be able to store the data in the analog memory 5. The video signal is stored in the same way as the video signal was stored.

On the other hand, the video signal stored in the analog memory 5 is read out at the timing of the clock pulse that has passed through the ζ2 frequency divider circuit 8. Therefore, the output of the analog memory 5 changes the time axis of the 2H signal of A to 2, as shown in the opening of Figure 3.
It appears doubled in size. This signal is led to a low-pass filter 9 and a bandwidth expander 11 via the b terminal of switch S4. The low-pass filter 9 is for extracting only the luminance signal. At the input of this low-pass filter 9, when considered in the frequency domain, the frequency of exactly half of that in Fig. 1, that is, the luminance signal is approximately 1
Up to 0 MHz, the color subcarrier frequency is 12.52 MHz. Since this signal is ultimately received by the receiver 20 for standard television broadcasting, the luminance signal is 4M.
m is sufficient. Therefore, the cutoff frequency of the low-pass filter 9 may be selected to be approximately 4 MHz. The band amplifier 11 is for passing only the color signal of 12.52 MHz±2.5 MHz. This color signal is used as the NTSC broadcast color signal 3. using the pilot burst P as a reference.
Circuits 12, 13, 1 convert to 58±0.5MHz.
4.15. A pulse with a timing corresponding to the pilot burst P is created from the synchronization signal obtained by the synchronization separation and pulse extraction circuit 16, and only the pilot burst P is extracted by the pilot burst gate circuit 13. The circuit 15 is a variable oscillator that oscillates at around 8.94 MHz, and a phase detector 14 compares the phase of the pilot burst P with the output of the variable oscillator 15, forming a phase lock loop that controls the variable oscillator 15 with this output. .
In the circuit of the frequency converter 12, a color signal around 12 MHz, which is the output from the band amplifier 11, and a carrier wave of 8.94 MHz, which is the output of the phase detector 14, are added, resulting in a signal of 3.58 MHz.
It is converted into a color signal centered on the center. If necessary, the bandwidth of the chrominance signal may be limited to approximately ±0.5 MHz using the band amplifier 11. The mixing circuit 10 adds the luminance signal obtained from the low-pass filter 9 and the color signal obtained from the frequency conversion circuit 12. In this way, a composite signal of NTSC general broadcasting is obtained, and by connecting this to the video signal input terminal of the receiver 20, it is possible to receive the contents of high-definition broadcasting. If it is necessary to input from the antenna terminal of the receiver 20, an RF converter may be provided between the mixing circuit 10 and the receiver 20. In addition, in the embodiment, explanation was given using analog memories 5 and 6, but instead of these, A
A similar configuration can be made using a /D converter, digital memory, and D/A converter.

Furthermore, in the configuration shown in Fig. 2, we have described the case where a pilot burst signal is inserted into the transmission signal, but the pilot burst is not necessarily necessary. A phase lock loop is constructed based on the burst signal read out from the 12.52 MHz carrier wave, and a color subcarrier frequency of 3.58 MHz is separately provided for the general NTSC system.
All you have to do is remove the bead with the MHz oscillator. That is, 1
It is possible to obtain a carrier wave similar to that obtained from a pilot burst, such as 2.52 - 3.58 = 8.94 MHz.

It is also possible to separate the luminance signal and color signal using a so-called "comb filter" in the luminance signal/chrominance signal separation circuit.The comb filter can extract luminance signals in a very wide band, so the image on the receiver If the amplifier has a wide band, an image with very good resolution in the horizontal direction can be obtained.Furthermore, although the embodiment has only described the reception of high-definition broadcasting having twice as many scanning lines, it is not necessary to As described above, according to the present invention, when high-definition broadcasting is started, time axis conversion is performed by using an appropriate memory element, and the current television receiver is Therefore, it becomes possible to receive the broadcast content, and there is a large degree of freedom in setting the frequency of the color subcarrier of the high-definition television signal, making it possible to provide an ideal high-definition image.

[Brief explanation of drawings]

FIG. 1 is a frequency spectrum of high-definition broadcasting, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a waveform diagram for explaining its operation. 5, 6... Analog memory, 7... Oscillation circuit, 8... Frequency divider circuit, 9... Low pass filter, 11... ... Bandwidth amplifier, 14...
・Phase detector, 15...Variable oscillator, 18...
...Frequency divider, 19...Phase comparator, 20...
...Receiver for standard television broadcasting.

Claims (1)

[Claims] 1. Storing a signal of one horizontal period of a high-definition broadcasting signal 2.
memory circuit, and while one of these memory circuits is writing, the other is reading, and when writing, the first clock pulse corresponding to the high-definition broadcast signal is used to write, and when reading, the standard television Time axis extension means for driving the memory circuit to read out data using a second clock pulse corresponding to a broadcast signal to extend the time axis;
a clock pulse generating means that generates the first and second clock pulses based on a burst signal of a high-definition broadcast signal; an oscillator that oscillates at a color subcarrier frequency of a standard television broadcast signal; a sine wave oscillator that oscillates based on the burst signal that has been received, and a frequency conversion circuit that takes beats based on the output of the second oscillator; A high-definition broadcast converter characterized in that the sine wave of the frequency conversion circuit is further frequency-converted to convert it into a standard television broadcast color signal. 2 Storing the signal of one horizontal period of high-definition broadcasting signal 2
memory circuit, and while one of these memory circuits is writing, the other is reading, and when writing, the first clock pulse corresponding to the high-definition broadcast signal is used to write, and when reading, the standard television Time axis extension means for driving the memory circuit to read out data using a second clock pulse corresponding to a broadcast signal to extend the time axis;
clock pulse generation means for generating the first and second clock pulses based on a burst signal of a high-definition broadcast signal; When converting, a reference sine wave for converting the color signal is superimposed on the image sending side in advance during the horizontal or vertical blanking period, separately from the burst signal for color signal demodulation, and the reference sine wave is superimposed on the image receiving side during the horizontal or vertical blanking period. The color signal of the high-definition broadcast after time axis expansion is converted into the color signal of the standard television broadcast by frequency-converting the color signal of the high-definition broadcast using a carrier wave created using the sine wave as a reference. Definition broadcast converter.