JPS6059883A - Television receiver - Google Patents

Abstract

PURPOSE:To attain accurate reception by using a signal subjected to waveform equalization when the change in a reception signal is processed by a universal filter and using the original signal when said change is not processed so as to perform the reception. CONSTITUTION:A slicer 19 is provided in parallel with a transversal filter 15, an output of a detection circuit 3 is delayed (16) and applied to the slicer 19. A waveform (a) stord in the transversal filter 15 and an output signal of the filter 15 are compared. When the output of the filter 15 is the waveform (a) and an output of a detection circuit 3 changes from (b) to (c), a high level signal is outputted from a comparator circuit 17. Then an output of an OR gate 22 becomes an output signal from the slicer 19. Accurate reception is performed by using the output of the slicer 19.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television receiver that receives television signals in which signals for displaying characters and graphics are multiplexed.

Conventional Structures and Their Problems So-called teletext broadcasting has been proposed as a means for multiplexing and transmitting separate new image information using a broadcasting signal. As shown in Figure 1A, this method utilizes the vertical blanking period of a normal television broadcast signal to display characters, figures, etc. in any horizontal scanning period (for example, the 20th H). A character multiplex signal, which is transmitted after being decomposed or encoded, is superimposed with a binary digital signal and transmitted.

This character multiplex signal has a certain number of bits (as shown in figure B).
It is composed of a group of digital signals (called data packets) of, for example, 260 bits, and its contents consist of a header section and an information data section. Depending on the information contained in the data part, there are packet types such as Page Control Bucket (PCP), Color Code Packet (CCP), and Pattern Data Packet (FDP). ) is transmitted before transmitting one screen of characters and graphics, and the data section contains page information such as program number (PR), page number (PA), and warning code for screen erasure or screen update (ED). Contains control code signals. color code bucket) (CC
P) is transmitted following the page control packet (PCP), and a color code (CC) indicating the color in which each character or unit division of characters and graphics should be displayed is transmitted.

Furthermore, the pattern data (FDP) is then transmitted continuously for one screen at a time (other packets may be inserted in the middle), and the data section contains the characters and figures to be displayed. Pattern data for each line is transmitted when scanning in the horizontal direction. This pattern data may be transmitted as a signal in which each character, graphic element, etc. is coded.

In addition, there are several other types of data packets,
The explanation will be omitted here.

In addition, the header section of every data packet contains a clock run-in signal (CR) for synchronizing the data sampling clock on the receiving side, a framing code signal (FC) for frame synchronization, and a service identification/ An interrupt control signal (SI/IN) and a data identification signal (DI, , DI2) indicating which type of data packet the data packet is are transmitted. Here, the FC signal is a signal capable of 1-bit error correction, and each of the SI/IN, Dll, and DI signals is a Hamming code capable of 1-bit error correction and 2-bit error removal. It is used.

Therefore, the receiving device receives the transmitted television signal with such text multiplex signals superimposed on it, extracts the text multiplex signal, and sends it to the page control bucket).
(PCP) to select only the signal of the program you want to receive, and select the color code data (CC) and pattern data packet in the color code packet (CCP) of that program.
(FDP) pattern data to digital memory
By accumulating data for a screen, reading it out in synchronization with the screen scanning of the cathode ray tube, and converting it into an image signal for display, the characters and figures can be displayed on the screen.

Generally speaking, a normal television receiver is also used to receive text and graphics, and a circuit is added to process the multiplexed signals, and when displaying the received characters and graphics, a cathode ray Characters, figures, etc. are displayed on the tube screen by superimposing the received image (moving image) of a normal television broadcast program, or by erasing the received image.

FIG. 2 shows a block diagram of an example of a television receiver that receives such a multiplexed signal. In the figure, 1 is a tuner, 2 is a VIP circuit, 3 is a detection circuit, 4 is a chroma signal and video signal processing circuit, 6 is a synchronization separation circuit, 6 is a horizontal oscillation circuit, and 7 is a color subcarrier (fsc) regeneration circuit. and
These are similar to the circuits of a normal color television receiver. 8 is a circuit that shapes the detected output signal into a binary code; 9 is a circuit that generates a write clock for sampling the multiplexed signal; 10 is a circuit that writes/reads data signals to/from the main memory 12; 11 is a circuit that generates a read clock for the main memory 12, 12 is a main memory, and 13 is a circuit that mixes or mixes the read output signal from the main memory 12 and the output signal of the chroma video processing circuit 4. The switching circuit 14 is a display cathode ray tube (CRT). Since its operation is well known, its explanation will be omitted.

By the way, the transmission system of television radio waves has many elements that degrade the signal waveform, such as the circuit frequency characteristics and phase characteristics of the transmitter, repeater, and receiver, as well as ghosts and reflections in the antenna system. It is necessary to equalize the waveform of the video detection output and return it to the same pulse waveform as on the sending side.

For this reason, in the past, a transversal filter was provided in the waveform shaping circuit 8 to perform waveform equalization.

However, since such transversal filters have a slow response speed, they cannot follow the rapid changes in the multiplexed signal being transmitted, and as a result, they inaccurately follow the waveform, which is an inconvenience. there were.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an apparatus that can eliminate such conventional disadvantages and supply as accurate a signal as possible to a multiplexed signal processing circuit even when the multiplexed signal fluctuates at high speed. purpose.

Structure of the Invention In the present invention, arithmetic processing is performed on a received signal that receives a phase control signal such as a chronograph-in signal that is placed at the beginning of a multiplexed signal and is sent with the same waveform every time. In addition to providing a filter that reproduces the same waveform as the waveform obtained by the filter, the phase control signal portion of the output signal of the filter is compared with the phase control signal of a predetermined waveform, and the difference between the two is determined to be equal to or greater than a certain value. In this case, the input signal to the filter is supplied to the multiplexed signal processing circuit, and when the difference between the two is less than a certain value, the output signal of the filter is switched to be supplied to the multiplexed signal processing circuit. There is.

By doing this, if the change in the received signal can be processed by the universal filter, the waveform-equalized signal is used, and if the change is too fast to be processed by the universal filter, it is not passed through the universal filter. In either case, the better signal can be used.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows a specific circuit diagram of the waveform shaping circuit 8 used in this embodiment, and FIG. 4 shows a waveform diagram of each part thereof.

In FIG. 3, 15 is a transversal filter, the configuration of which may be already known. Generally, as shown in Figure 4, of the received multiplexed signal, only the chronograph-in signal CRI or the CRI signal and frame are used.
In order to obtain a signal a with a predetermined pulse waveform for the timing code signal FC (this waveform a is stored in the filter 15 in advance), the detection output signal S is sampled at high speed, and the signals a and b are The weighting coefficients for each tap of the transversal filter 15 are calculated by a microcomputer or the like so that the difference between the waveforms is reduced to zero, and the weighting is done by controlling the coefficients appropriately. Equalize the waveform of as shown in a.

On the other hand, due to some temporary reason, the waveform of the detection output signal is
In the case of a change from C to C, the weighting coefficient for equalizing b to a is C(l-j:a), and the procedure for such a case will be described later.

Within the transversal filter 15, sampling is required at least twice per bit of the multiplexed signal. An example of such a sampling pattern is shown in FIG. 4d. Comparison with waveform a is based on sampling clock d
Stop at @. The reason for this is that when the detection output signals S, C, etc. are sampled at the sampling clock O20, depending on whether the first bit of the signal SI/IN following the framing code signal FC is "○" or "1". This is because the output value obtained changes.

Now, generally speaking, by increasing the computation time of the transversal filter, the waveforms of the detection output signals (a) and (c) can be brought closer to a. However, if it is too long, for example,
When the waveform of the detected output signal changes from B to C, such as when switching channels on a television receiver, it takes time for the output waveform of the transversal filter to return to A, and during that time it is difficult to receive the multiplexed signal correctly. Can not. Assuming that the calculation requires time for 180 fields, since one screen of characters and graphics generally consists of 204 lines, the transmission time when transmitting only white characters would be 3.4 seconds ( 204 fields) for 3 seconds (
180 field) cannot be received, and one screen's worth of characters and graphics may be omitted and displayed.

Therefore, in this apparatus, as shown in FIG. 3, a slicer 19 is provided in parallel with the transversal filter 15, the video signal output from the detection circuit 3 is delayed by the delay circuit 16, and the output is applied to the slicer 19.

On the other hand, a comparison circuit 17 compares the waveform a stored in the transversal filter 15 with the output signal of the transversal filter 15. If the output of the detection circuit 3 changes from b to C when the output of the transversal filter 15 is a, a difference will occur if the two are compared in the comparator circuit 17. This comparison is shown in Figure 4 d.
~Let's follow @'s clock. Even if the determination is made by a microcomputer, the time required is 1
A time equivalent to a field is sufficient, and when a predetermined amount of difference is exceeded, a high level signal is output as the output of the comparator circuit 17.

When the output of the comparison circuit 17 becomes high level, the output of the inverter 18 becomes low level, the AND gate 21 is cut off, and the AND gate 20 becomes conductive, so the output of the OR gate 22 becomes the output from the slicer 19. It becomes a signal. That is, when the difference between the waveform of the output of the transversal filter 15 and the waveform a is greater than a certain value, the output signal of the slicer 19 is supplied to the multiplexed signal processing circuit as the output of the OR gate 22. Therefore, it is possible to receive character/graphic signals using this.

The delay circuit 16 is inserted to eliminate the phase difference between the output of the slicer 19 and the output of the transversal filter 15. Note that it is also possible to include the comparison circuit 17 in the transversal filter 15.

It is good, a timer circuit is provided in the comparison circuit 17, and 2 to 3
Only when the output of the transversal filter 15 deviates from waveform a by more than a certain value in consecutive fields, the output of the comparator circuit 17 is changed to a high level so that short-term signal fluctuations in only 1 to 2 fields are ignored. It is more practical to do so.

According to such a circuit, the signal waveform changes to C and becomes 1
If the output of the comparison circuit 17 becomes high level after the field, the received signal for one field, that is, the signal for one packet, is processed by the transversal filter 15.
1.
After the field, the output of the slicer 19 which has not passed through the Lanceversal filter 15 will be used.

As this slicer 19, a slicing circuit is used so that when the received multiplexed signal has a normal waveform, the waveform of its slice output is the same as the pulse waveform on the sending side.

In this case, a signal with a waveform like the detection signal C is sent to the slicer 1.
Although the same waveform as the transmitted waveform cannot be obtained by slicing with Although most of the output from the slicer 19 has a waveform that is close to normal, compared to the large waveform distortion caused by the transversal filter 1
This results in more accurate reception than using the output of 5.

Furthermore, during the period when the comparison output of the comparison circuit 17 is at a high level, the warning generating circuit 23 lights up a lamp or displays characters or the like on the TV screen indicating an abnormality in the reception status, thereby changing the character/graphic screen. It is possible to notify the viewer that the reception status is not normal.

Effects of the Invention As described above, according to the present invention, 1. Normally, by using a received signal whose waveform has been equalized by an arithmetic filter such as a transversal filter, characters and characters can be created using the signal whose waveform has been accurately equalized. It is possible to receive multiplexed signals such as graphics, and when the waveform of the received signal changes suddenly, it is more accurate by using the input signal instead of using the output of a filter that cannot handle it. This allows for accurate reception.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the transmission mode of teletext broadcasting, FIG. 2 is a block diagram of a conventional television receiver, and FIG. 3 is a block diagram of a television receiver according to an embodiment of the present invention. Figure 4 is a waveform diagram of each part. 1 Tuner, 2...VIP circuit, 3 Video detection circuit, 4...Chroma/video processing circuit, 8 Waveform shaping circuit, 9...Write clock generation circuit, 10...Write/
Read processing circuit, 11・Read clock generation circuit, 12・
...Main memory, 13...Mixing/switching circuit, 14
... CRT, 15-1-Lance Barzal filter, 16 ... Delay circuit, 17 ... Comparison circuit,
18...Inverter, 19...Slicer, 20
．． 21...AND gate, 22...OR
Gate. Name of agent: Patent attorney Toshio Nakao and one other person Published by Japanese Patent Application Publication No. 8-8; 0-59883 (5)

Claims (2)

[Claims] (1) A multiplexed signal representing characters and figures sent superimposed on a television signal is received and stored in a digital memory, and is displayed vertically on the preview screen. The contents of the memory are read out in accordance with horizontal scanning to display characters and figures on the television screen, and the phase control is placed at the peak of the multiplexed signal and sent with the same waveform every time. a filter that performs arithmetic processing on a received signal to reproduce a waveform identical to a predetermined waveform; When the difference between the two is greater than a certain value, the input signal to the filter is supplied to the multiplexing signal processing circuit, and when the difference between the two is less than a certain value, the input signal to the filter is supplied to the multiplexing signal processing circuit. A television receiver comprising a comparison circuit and a switching circuit for switching an output signal to be supplied to the multiplexed signal processing circuit. (2) Claims characterized in that the input signal of the filter is supplied to the multiplexed signal processing circuit when a period in which the difference between the input signal and the output signal of the filter continues for a certain value or more continues for a certain period of time or more. The television receiver according to paragraph 1.