JPH01251970A - Waveform equalizing device for teletext - Google Patents

Abstract

PURPOSE:To attain normal waveform equalization when a ghost is returned to a normal ghost by deciding whether a framing code(FC) is detected from a waveform equalization output at the multiplex line of a character multiplexing signal or not when the number of the times of correcting a tap gain reaches the prescribed number of times and setting the value of the tap gain to an initial value when the FC is not detected. CONSTITUTION:An FC detecting circuit 40 detects the FC from the output of a binarizing circuit 33 at a line on which the character multiplexing signal is superimposed. This detected output is supplied to a CPU 41, and the CPU 41 decides whether the FC is detected or not when the number of time of correcting the tap gain reaches the prescribed number of times, sets the value of the tap gain to the initial value when the FC is not detected, and decides whether the FC is detected every time or not while correcting the tap gain when the FC is detected. Thus, the divergence of the tap gain due to a ghost fluctuation can be prevented, and a normal waveform equalizing operation can be executed when the ghost fluctuation is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a waveform equalization device used for waveform equalization of a teletext multiplex signal in a teletext broadcasting receiver.

(Prior Art) FIG. 7 shows the configuration of a conventional waveform equalization device for teletext broadcasting.

In FIG. 7, numeral 11 is an input terminal to which a television signal multiplexed with a character multiplex signal is supplied. The television signal supplied to this input terminal 11 is supplied to a waveform equalizer 12, and after being waveform-equalized into a predetermined waveform, it is taken out from an output terminal 13.

The television signal supplied to the input terminal 11 is further supplied to a character multiplex signal detection circuit 14.

This character multiplex signal detection circuit detects a horizontal scanning period (hereinafter referred to as a line) in which a character multiplex signal is superimposed from an input signal, and supplies a necessary timing signal to the control section 15. The control unit 15 controls the tap gain memory and the like of the waveform equalizer 12 according to this timing signal.

(Problems to be Solved by the Invention) In the conventional waveform equalization device described above, when the waveform equalization operation is normal, if the ghost temporarily fluctuates due to the influence of an airplane, etc., the tap gain may change. There is a problem in that even if the ghost diverges and returns to a normal ghost, normal equalization processing may not be performed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a waveform equalization device for teletext broadcasting that can prevent tap gain divergence due to ghost fluctuations and perform normal waveform equalization operation when ghost fluctuations disappear. shall be.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides means for detecting a line on which a character multiplex signal is superimposed from a television signal supplied to a waveform equalization means. , means for detecting the number of corrections or correction time of the tap gain of the transversal filter from the waveform equalization means, when the number of corrections or correction time reaches a predetermined number or time;
A means for determining whether or not a character multiplex signal is erroneously waveform equalized on a line on which the character multiplex signal is superimposed; In this embodiment, a means for setting the value is provided.

(Function) If the tap gain fluctuates due to ghost fluctuations, normal waveform equalization will not be achieved even if the tap gain is corrected.
Therefore, as described above, according to the configuration in which it is determined whether or not the character multiplexed signal has been erroneously waveform equalized when the number of corrections or the correction time of the tap gain reaches a predetermined number of times or a predetermined time, the tap gain It is possible to detect that the is about to diverge. And in such a case,
In the above configuration, the tap gain is set to a predetermined value, so
When ghost fluctuations disappear, normal waveform equalization operation can be performed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

The configuration and operation of one embodiment will be described in detail below with reference to FIGS. 2 to 5.

Figures 2 and 3 are waveform diagrams showing character multiplex signals, and Figure 4 is the framing code (hereinafter referred to as F) shown in Figure 1.
5 is a circuit diagram showing an example of a specific configuration of the detection circuit 40 (denoted as C), and FIG. 5 is a flowchart not shown in FIG. 1 but showing the operation of the CPU 41.

First, a character multiplex signal will be explained using FIGS. 2 and 3.

In teletext broadcasting, a teletext signal having a configuration as shown in FIG. 2 is superimposed on the vertical retrace period of a television signal, and is sent discretely as packets.

At the beginning of each data bucket, there is a clock run-in (hereinafter referred to as CI') of the data pattern as shown in Figure 3.
On the receiving side, tarok playback is performed using this data pattern.

Therefore, in order to reproduce the clock, it is first necessary to detect the arrival of the CRI signal. In addition, when waveform equalization is performed using a waveform equalization device for teletext broadcasting, M
It is necessary to perform waveform equalization using only the numerically transmitted character multiplexed signal. Therefore, the tap gain of the transversal filter is corrected only on the line where the CRI signal is detected.

Now, returning to FIG. 1, the configuration and operation of the waveform equalization device will be explained.

The television signal supplied to the input terminal 11 is sent to an analog/digital conversion circuit (hereinafter referred to as an A/D conversion circuit).
After being converted into a digital signal by 31, the waveform is equalized by transversal filter 32. This waveform equalized output is converted into a binary signal by the 2i conversion circuit 33, and then decoded by a teletext decoder (not shown) connected to the output terminal 13.

The sampling clock of the A/D conversion circuit 31 is generated as follows.

The television signal supplied to the input terminal 11 is further supplied to a phase difference detection circuit 34 and a CRI detection circuit 35. The phase difference with the output of the conversion circuit 31 is detected and output, and the detected output is sent to the clock generation circuit 3.
Supply to 6. This clock generation circuit 36 generates a sampling clock for the A/D conversion circuit 31, and generates a sampling clock having an optimal phase for punching out the peak of the CRI signal according to the phase difference detection output. As a result, in the A/D conversion circuit 31,
The character multiplex signal, which is a binary signal, is sampled at its peak and supplied to the transversal filter 32 as an A/D converted digital signal. The CRI detection circuit 35 is
The four-phase detection circuit 34 detects the CRI signal from the input signal and supplies the position information to the phase detection circuit 34. Based on this position information, the four-phase detection circuit 34 detects the phase difference between the two input signals only in the CR1 section.

The tap gain of the transversal filter 32 is controlled as follows.

The subtraction circuit 37 takes the difference between the output of the transversal filter 32 and the output of the binarization circuit 33, and supplies a signal representing this difference to the tap' gain control circuit 38 as an error signal. Tap gain control circuit 38 supplies memory 39 with a control signal that modifies the tap gain in a direction that reduces the difference indicated by the error signal. The memory 39 includes the CRI detection circuit 3
5 stores the input control signal only on the line where the CRI signal is detected and supplies it to the tap gain memory 40. On the other hand, in lines where no CRI signal is detected, the previous value is held. By doing so, waveform equalization can be performed using only the discretely sent character multiplexed signal. The tap gain memory 40 supplies the transversal filter 32 with a gain signal indicating a tap gain according to the input control signal, and controls the waveform equalization process of the filter 32.

The FC detection circuit 40 detects the FC from the output of the binarization circuit 33 in the line on which the character multiplex signal is superimposed, according to the signal output from the CRI detection circuit 35 and indicating whether the line is on which the character multiplex signal is superimposed. Detect. This detection output is supplied to the CPU 41. The CPU 41 has
Furthermore, from the tap gain control circuit 39, the current
A signal indicating whether the knob gain is modified is provided. The CPU 41 determines from these two input signals whether or not to set the data in the tap gain memory 40 to the initial value.

Next, the configuration and operation of the FC detection circuit 40 will be explained using FIG. 4.

In this FIG. 4, the input terminal 51 is connected to the binarization circuit 3.
3 outputs are provided. Here, FC is 4/5
Since the data is fixed as "11100101" at a clock rate of fec, the output of the binarization circuit 33 supplied to the input terminal 51 is supplied to an eight-stage shift register 52 that operates at a tarok of 415 fec. Ru. The 8-bit data stored in this shift register 52 is
F by inverter 53, 54, 55 and NAND circuit 56
It is determined whether or not C. If it is FC, NAND circuit 5
6 becomes low level. This judgment output is supplied to an OR circuit 57.

The input terminal 58 is supplied with a signal indicating whether or not the line is overlaid with a character multiplex signal output from the CRI detection circuit 35. This signal is supplied to the OR circuit 57, the D flip-flop 1 circuit 59, and the OR circuit 60. The signal supplied to the input terminal 58 is at a low level when indicating a line on which a character multiplex signal is superimposed, and is at a high level when indicating a line on which a character multiplex signal is not superimposed. As a result, the output of the OR circuit 57 becomes low level only when a line on which a character multiplex signal is superimposed is detected and FC is detected. The output of this OR circuit 57 is supplied to a set terminal S of a flip-flop circuit 61.

The D flip-flop circuit 59 and the OR circuit 60 detect the falling timing of the f5 signal supplied to the input terminal 58, and output a low level signal at the detected timing. This signal is supplied to the reset terminal R of the flip-flop circuit 61. Therefore, the flip-flop circuit 61 is reset when the output of the OR circuit 60 goes low, and is set when the output of the OR circuit 57 goes low. As a result, the flip-flop circuit 6
The Q output of 1 becomes high level only when FC is detected in the line on which the character multiplex signal is superimposed, and becomes low level during other periods.

The Q output of the flip-flop circuit 61 is supplied to the CPU 41 from an output terminal 62 as an FC detection output.

Finally, the operation of the CPU 41 will be explained with reference to FIG.

In step S1 of FIG. 5, the tap gain stored in the tap gain memory 40 is set to the initial value. In step S2 of the 0th order, the count value T of the counter that counts the number of times the tap gain is corrected is set to 0. In the 0th step S3, the count value T is incremented by 1 every time the tap gain is corrected.In the 6th step S4, the tap gain is corrected in the 6th step S5.
Then, it is determined whether the number of tap gain corrections (count value T) is equal to or greater than N. If it is less than N, the process returns to step S3 and the number of corrections is counted. If it is N or more,
After the tap gain is corrected in step S6, FC is detected in step S7. In the zero-order step S8, it is determined whether or not FC is detected. If detected, the process returns to step S6, and the tap gain is adjusted. Corrections will be made. If not detected, the process returns to step S1 and the tap gain is set to the initial value.

In this way, when the number of corrections of the tap gain reaches N, the CPU 41 determines whether or not FC is detected, and if it is not detected, sets the tap gain to the initial value, and if it is detected, , FC each time while modifying the tap gain.
is detected.

As described in detail 3=lPt above, in this embodiment, when the number of tap gain corrections reaches a predetermined number, it is determined whether or not FC is detected from the waveform equalization output in the multiplex line of the character multiplex signal. When it is not detected, the tap gain is set to the initial value. Therefore, according to this embodiment, even if the tap gain diverges due to ghost fluctuations caused by an airplane or the like, a malfunction in waveform equalization can be detected and normal waveform equalization can be performed. Further, such an effect can be applied even when the tap gain converges to an incorrect value and waveform equalization is not performed normally.

In addition, in this invention, in order to determine whether waveform equalization has been performed normally, instead of the FC detection circuit 40 in FIG.
A CRI detection circuit 43 may be provided and the determination may be made based on whether or not the CRI signal can be detected.

In addition to this, it is also possible to detect and judge data with a fixed pattern, which is essential for a character multiplex signal.

Also, if the waveform is not equalized normally, the initial value set to the tap gain may be set to, for example, the last value when it is determined that the waveform has been equalized normally. good.

Furthermore, in the previous embodiment, when the number of tap gain corrections reaches a predetermined number, for example, it is determined whether or not FC is detected. However, as shown in FIG. The determination may be made when a predetermined time N has been reached.In addition, in FIG.
Corresponding to step S1 in the figure, step S10 is a step for determining whether or not a predetermined time period N has been reached, and steps 311, 812, and 813 are as shown in FIG.

This step corresponds to S7.38.

It goes without saying that various other modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, even in an environment where the tap gain diverges or converges to an incorrect value, this can be prevented and the current returns to a normal ghost. If
Normal waveform equalization can be performed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
3 and 3 are signal waveform diagrams for explaining the operation of FIG. 1, FIG. 4 is a circuit diagram showing an example of a specific configuration of the FC detection circuit shown in FIG. 1, and FIG. FIG. 6 is a circuit diagram showing the configuration of another embodiment of the invention; FIG. 7 is a flowchart showing the operation of still another embodiment of the invention; FIG. 1 is a circuit diagram showing the configuration of a conventional waveform equalization device. DESCRIPTION OF SYMBOLS 11... Input terminal, 12... Equalizer, 13... Output terminal, 14... Character multiplex signal detection circuit, 15...
Control unit, 21...Character multiplex signal error detection circuit, 22.
...Tap gain memory setting circuit, 31...A/D conversion circuit, 32...Transversal filter, 33...
・Binary circuit, 34... Phase difference detection circuit, 35...C
RI detection circuit, 36... Clock generation circuit, 37...
・Subtraction circuit, 38...Tap gain control circuit, 39...
・Memory, 40...Tag gain memory, 41...C
PU, 43...CRT detection circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 5 Figure 7

Claims (5)

[Claims] (1) a waveform equalization means for equalizing the waveform of the text multiplex signal multiplexed with the television signal by controlling the tap gain of a transversal filter to which the text multiplex signal multiplexed with the television signal is supplied; a multiplex period detection means for detecting a horizontal scanning period in which the character multiplex signal is multiplexed in a television signal supplied to the waveform equalization means and in which the character multiplex signal is multiplexed; and the tap of the waveform equalization means. a correction number detection means for detecting the number of corrections of the gain; and when the number of corrections detected by the correction number detection means reaches a predetermined number, in the multiplex horizontal scanning period of the character multiplex signal detected by the multiplex period detection means; , determining means for determining whether or not the waveform of the character multiplex signal has been erroneously equalized by the waveform equalizing means; and determining means for determining whether the character multiplex signal has been erroneously waveform equalized by the determination means and tap gain setting means for setting the tap gain of the waveform equalization means to a predetermined value when the waveform equalization means is set to a predetermined value. (2) a waveform equalization means for equalizing the waveform of the text multiplex signal multiplexed on the television signal by controlling the tap gain of a transversal filter to which the text multiplex signal multiplexed on the television signal is supplied; a multiplex period detection means for detecting a horizontal scanning period in which the character multiplex signal is multiplexed in a television signal supplied to the waveform equalization means and in which the character multiplex signal is multiplexed; and the tap of the waveform equalization means. a correction time detection means for detecting a gain correction time; and when the correction time detected by the correction time detection means reaches a predetermined time, in the multiple horizontal scanning period of the character multiplex signal detected by the multiple period detection means. , determining means for determining whether or not the waveform of the character multiplex signal has been erroneously equalized by the waveform equalizing means; and tap gain setting means for setting the tap gain of the waveform equalization means to a predetermined value when the waveform equalization means is set to a predetermined value. (3) The determining means detects data of a specific pattern multiplexed on the multiplexed text signal, and determines whether or not the multiplexed text signal is erroneously waveform-equalized based on the presence or absence of data of the specific pattern. 3. The waveform equalization device for teletext broadcasting according to claim 1 or 2, characterized in that it is configured to perform the following. (4) The character multiplexing waveform equalization device according to claim 3, wherein the specific pattern data is a Fleming code. (5) The character multiplexing waveform equalization device according to claim 3, wherein the specific pattern data is a clock run-in signal.