JPS6128275B2 - - Google Patents

Description

Detailed Description of the Invention The present invention detects the position of a test signal for waveform distortion detection using an automatic waveform equalizer from an input signal, and accurately determines the reference point by counting a fixed number of counts from the regenerated horizontal synchronization signal. The present invention relates to a pulse position detection method in which the pulse position is determined.

Conventionally, in television (TV) signals, a vertical blanking interval test signal (VITS) is used as a test signal for detecting waveform distortion, and the received waveform is sampled by a transversal automatic equalizer. A commonly used method is to detect waveform error information by comparing it with a reference waveform, and adjust the gain of the equalizer tap in accordance with this information for equalization. In this case, the important point is that the error information of the detected waveform and the information for tap control correspond correctly.

In the conventional waveform equalization method, a counter takes a fixed number of counts in advance from a signal that serves as a reference position, such as a horizontal synchronization signal, and uses it as a reference point for detecting waveform distortion of VITS.

As a test signal, the
Using a 2T pulse (sin ² pulse), we will explain a method for detecting the peak position of the 2T pulse in order to correctly match waveform distortion error information with information for tap control.

FIG. 1 shows the configuration of a conventional transversal automatic waveform equalizer. In the figure, the TV signal is branched from the output side through the equalizer 1 and input to the detector 2, and the received waveform in which the 2T pulse is detected is compared with a reference waveform prepared in advance to detect error information and take appropriate action. Automatic waveform equalization is performed by supplying the tap control information to the equalization section 1.

FIGS. 2a to 2g are schematic explanatory diagrams showing the conventional procedure for detecting the position of a 2T pulse.

The 2T pulse rides on the 17th horizontal synchronization period (17H) of the first field of the TV signal shown in Figure a, and Figure b is an enlarged view of 17H.

The detection unit 2 that detects waveform distortion for controlling the automatic waveform equalizer shown in Fig. 1 separates the synchronization from the TV signal and reproduces the horizontal synchronization signal, and the phase-locked oscillator (PLO) described later in the example Sample the pulse and detect the peak. Therefore, timing clocks synchronized with the rising edge of the horizontal synchronizing signal shown in FIG. 2B are generated for a fixed number of counts, as shown in FIG. d and the following are detailed enlarged waveform diagrams showing peak detection. That is, the peak of the 2T pulse is detected, and a predetermined number of pieces of error information, including those before and after this error information, are used as a reference point to correspond to the tap control information. Therefore, d and e in the same figure
As shown in the figure, after clearing the counter at the rising edge of the 17H horizontal synchronization signal (dotted line A), the above-mentioned timing clock is counted by the preset fixed count number N, and the peak of the 2T pulse (dotted line B) is detected. However, in order to more accurately match the peak of the 2T pulse, adjustment is made using a timing automatic phase tracking circuit (TAPC), which will be described later, as shown in FIG.
The information sampled by the timing clock whose peak has been detected in this way controls the center tap gain as information 2 for controlling the center tap of the equalizer 1 shown in FIG. Waveform equalization is performed by correlating error information obtained by detecting waveform distortion at other sampling points with tap control information using the peak detection timing as a reference point.

However, the detection section 2 for detecting waveform distortion for controlling the equalization section 1 of the automatic waveform equalizer shown in FIG.
Since the TV signal is a horizontal synchronization signal that is synchronized and separated from the TV signal that has passed through the equalization section 1, the rising edge of the horizontal synchronization signal fluctuates due to fluctuations in the equalization section 1. Then, the timing clock generated in phase synchronization with the horizontal synchronization signal by the phase synchronization oscillator will have jitter, and the position counted by the fixed number will not be determined. Furthermore, when automatic phase tracking is used to accurately align the timing clock with the position of the 2T pulse, an uncertain phase shift occurs between the rising edge of the horizontal synchronization signal, that is, the counter clear point, and the counter timing clock. After clearing the counter, the first clock input to the counter is not determined, and for example, as shown in figure f, the peak detection position is miscounted and automatic phase tracking is performed corresponding to the Nth timing clock. In this case, even though the N+1st position is detected, the Nth position is mistakenly detected as the peak position. Therefore, as shown in g in the same figure, the information for tap control should be ``d'' but becomes ``c'', and the error information for waveform distortion detection and the information for tap control no longer correspond, making correct control impossible. Become.

The purpose of the present invention is to detect the position of a test signal for detecting waveform distortion using an automatic waveform equalizer from an input signal, and to detect the position of a test signal for detecting waveform distortion by counting a fixed number of counts from a regenerated horizontal synchronization signal to accurately determine a reference point. An object of the present invention is to provide a position detection method.

In order to achieve the above object, the pulse position detection method of the present invention uses an automatic waveform equalizer that detects waveform distortion using a vertical blanking interval test signal (VITS) of a TV signal as a test signal and performs automatic waveform equalization, After specifying the position of the horizontal synchronization section including the test signal based on the horizontal synchronization signal reproduced from the TV signal after waveform equalization output from the automatic equalizer, the timing clock is clocked by a fixed count number. In the pulse position detection method, which detects the position of the test pulse by counting the
A clock is extracted from the TV signal, a timing clock is generated from the clock, the regenerated horizontal synchronization signal is reread by a clock obtained by dividing the timing clock, and the timing is determined based on the reread horizontal synchronization signal. This method is characterized in that the position of the test signal (VITS) in the horizontal synchronization section is specified by counting a fixed number using a clock as a count clock.

The present invention will be described in detail below with reference to examples.

FIGS. 3a to 3j are explanatory diagrams of the principle of the present invention.

As described above, due to fluctuations in the equalization section 1 of the automatic waveform equalizer, the rising edge of the horizontal synchronizing signal fluctuates, causing the timing clock to have jitter. In order to prevent this, the TV signal shown in FIG. 3a is branched before the equalizer 1 and synchronously separated. Then, the horizontal synchronization signal shown in FIG. In addition, since the TV signal is delayed in the equalization unit 1, the horizontal synchronization signal that is branched from before the equalization unit 1 and reproduced is synchronized and separated from the TV signal shown in FIG. As shown, the phase is shifted from the horizontal synchronizing signal of d in the same figure. For this purpose, the horizontal synchronization signal reproduced from the detection unit 2 shown in figure d is prepared, and then the timing clock shown in figure h is automatically phase-tracked to the peak of the 2T pulse (dotted line b) shown in figure e. A clock is generated by dividing the frequency of the timing clock shown in FIG. A certain point in time of this clock is shown by a solid line, and a dotted line shows the clock after the phase has changed due to automatic phase tracking, and its movement is shown by an arrow. Now, using the solid line clock, the horizontal synchronizing signal reproduced by the detecting section 2 is reread using, for example, a DFF flip-flop, as shown in g in the figure. The counter is cleared (dotted line A) at the rising edge of the reread horizontal synchronizing signal 17H in g of the same figure.
Note that the clear points occur at two locations corresponding to the solid line clock and the dotted line clock in FIG.

Based on the previous clear point, the timing clock is counted by a preset fixed count number N, and the peak of the 2T pulse (dotted line b) is detected, as shown in h of the figure. However, since there is an error with this alone, automatic phase tracking is performed. That is, as shown in Figure i, automatic phase tracking is performed to the peak of the 2T pulse using a timing clock that corresponds to the dotted line clock in Figure F and is based on the clear point after Figure G.

This automatic phase tracking uses a method of sampling the timing clock at regular intervals and comparing it with a reference potential to search for the potential near the peak of the 2T pulse (dotted line B). Then, phase control is applied so that the difference between the standard potential at the dotted line (R) and the sampling potentials on the left and right thereof approximates zero. In this case, the phase relationship between the counter clear point and the timing clock is constant as shown in f, g, h, and i in the same figure, and the clock that is first input to the counter after clearing at h in the figure is determined. This is followed by the automatic phase tracking clock shown in figure i, and the corresponding tap information shown in figure j is determined centrally. In this way, the error information for waveform distortion detection and the information for tap control are correctly correlated.

FIG. 4 is an explanatory diagram showing the configuration of an embodiment of the present invention. In the figure, an echo signal inputted from an input terminal 11 to a transversal filter 12 and whose gain was adjusted by the aforementioned gain adjustment tap 13 and a main signal are combined by a collective amplifier 14.

This TV signal is transmitted to the horizontal synchronization reproducing circuit (detection section) 1
8 reproduces the horizontal synchronization signal and outputs the peak detection circuit 19.
send to In addition, the horizontal synchronization reproducing circuit 21 regenerates a horizontal synchronization signal from the TV signal before the equalizer, the phase synchronization oscillator 22 regenerates a timing clock that is phase synchronized with the horizontal synchronization signal, and the timing automatic phase tracking circuit 20 reproduces a 2T Automatic phase tracking to pulse peak. The peak detection circuit 19 rereads the horizontal synchronization signal reproduced by the horizontal synchronization regeneration circuit 18 using a clock obtained by dividing the timing clock, clears the counter at the rising edge of the horizontal synchronization signal at 17H, and sets the timing clock in advance. The fixed count number N is counted, and the peak of the 2T pulse is detected. The sampling circuit 16 converts the TV signal output from the equalization section into a timing automatic phase tracking circuit 20.
The signal is sampled using a timing clock with automatic phase tracking, and the identification circuit 17 compares it with a reference waveform to obtain waveform distortion error information. Error information at the peak of the 2T pulse is detected from the peak of the 2T pulse detected by the peak detection circuit 19, and information for controlling the advance -l tap to the delay +m tap is input to the shift register 23 based on the error information. The information input to the shift register 23 is converted into an analog signal by the integrator 24, and the information input to the shift register 23 is converted into an analog signal by the integrator 24, and the information input to the shift register 23 is
The gain of 3 is adjusted, and the waveform-equalized TV signal is extracted from the output of the output terminal 15.

As explained above, according to the present invention, a clock is extracted from a TV signal before input to an automatic waveform equalizer, a timing clock is generated from the clock, and the reproduced horizontal This method rereads the synchronization signal and specifies the position of the horizontal synchronization section based on the reread horizontal synchronization signal. This confirms the detection of the timing clock from the horizontal synchronization signal, so there is no error in waveform distortion detection. Equalization can be performed effectively by correctly correlating the information with the information for tap control.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of the conventional example, Fig. 2 a to g is a schematic explanatory diagram of the procedure of the conventional example, Fig. 3 a to j is an explanatory diagram of the principle of the present invention, and Fig. 4 is an embodiment of the present invention. is a configuration explanatory diagram, in which 1 is an equalization section, 2 is a detection section,
11 is an input terminal, 12 is a transversal filter, 13 is a gain adjustment tap, 14 is a collective amplifier, 15 is an output terminal, 16 is a sampling circuit, 1
7 is an identification circuit, 18 is a horizontal synchronization regeneration circuit, 19 is a peak detection circuit, 20 is a timing automatic phase tracking circuit, 21 is a horizontal synchronization regeneration circuit, 22 is a phase synchronization oscillator, 23 is a shift register, and 24 is an integrator. .

Claims (1)

[Claims] 1 TV signal vertical blanking interval test signal (VITS)
Using an automatic waveform equalizer that detects waveform distortion and performs automatic waveform equalization as a test signal, test using the horizontal synchronization signal reproduced from the TV signal after waveform equalization output from the automatic equalizer as a reference. In the pulse position detection method, which detects the position of the test pulse by counting the timing clock a fixed number of times after specifying the position of the horizontal synchronization section including the signal, A clock is extracted from the TV signal, a timing clock is generated from the clock, the regenerated horizontal synchronization signal is reread by a clock obtained by dividing the timing clock, and the timing is determined based on the reread horizontal synchronization signal. A pulse position detection method characterized in that the position of the test signal (VITS) in the horizontal synchronization interval is specified by counting a fixed number using a clock as a count clock.