KR920009727B1 - Automatic phase compensation apparatus of high definition tv - Google Patents

Abstract

The compensator for correcting the phase difference of receiving signal in high definition television (HDTV) comprises: a phase detector and comparator (120) detecting and correcting the phase by using the input data of the phase compensator; a digital/analog convertor (130) and the loop filter (140) connected to the output terminal of the comparator (120); a voltage control oscillator generating the control frequency of analog/digital convertor (60) by inputting the outputted value of the loop filter. The data of the phase compensator is automatically switched by the transmission system and the non-transmission system. This compensator is useful for minimizing the image degradation.

Description

Auto Phase Compensator for High-Definition TVs

1 is a block diagram of a high definition TV receiver to which the present invention is applied.

2 is the HD waveform and VCO output.

3 is a circuit diagram of an automatic phase compensator of the present invention.

* Explanation of symbols for the main parts of the drawings

10: receiver 20: deemphasis circuit

30: multiplexer 40: amplifier

50: low pass filter 60: A / D converter

70: input processing controller 100: automatic phase corrector

110: time window 120: phase detection and comparison unit

130: D / A converter 140: loop filter

150: voltage controlled oscillator 160: multiplexer

170: transmission system phase correction 180: non-transmission system phase correction

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic phase corrector for correcting the phase error of a received signal, in particular in the receiver of a high definition television. The MUSE signal of the high definition television system is band-compressed to 8MHZ at the transmitter and transmitted to the receiver via satellite.

Therefore, since the signal received by the receiver is sub-sampled and information is reduced, the interpolation process is performed to restore the received signal. However, in order to recover the correct playback signal by interpolation, the accurate resampling phase must be maintained. However, due to group delay during satellite transmission and overshoot or undershoot of the synchronization signal, the resampling ( Re-Sampling phase occurs, resulting in deterioration of image quality.

In order to solve such a deterioration of image quality, an automatic phase compensator is used in a receiver. In the related art, an analog PLL (Phase Locked Loop) has a problem of extremely low precision. Likewise, decoding of a sub-sampled signal at a high frequency was not appropriate.

The present invention has been conceived to improve the above-mentioned disadvantages, for high-definition TV that accurately generates an incorrect re-sampling clock due to the overshoot and undershoot of HD waveforms, which are the criteria for group delay and phase comparison per frame. It is an object of the present invention to provide an automatic phase compensator. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a receiver of a high definition TV to which the automatic phase compensator of the present invention is applied. 1 shows the receiver 10, the de-emphasis circuit 20, the amplifier 40, the low pass filter 50, the A / D converter 60, and the receiving circuit of the known auto phase corrector 100 of the present invention. Is configured from an output signal terminal of the A / D converter 60 to feed back the output signal to the A / D converter 60. In addition, in the present invention, the multiplexer 30 and the input processing control unit 70 are configured between the de-emphasis circuit 20 and the amplifier 40 so as to switch between the non-transmission system signal and the transmission system signal. The automatic phase compensator 100 of the present invention comprises a closed loop with a time window 110, a phase detection and comparison unit 120, a D / A converter 130, a loop filter 140, and a voltage controlled oscillator 150. The output of the voltage controlled oscillator 150 is applied to the A / D converter 60, and the phase comparison and detection unit 120 transmits the transmission system through the multiplexer 160 controlled by the input processing control unit 70. It is configured to receive one of the data of the phase correction unit 170 and the non-transmission system phase correction unit 180 as a comparison signal. Referring to the operation of the automatic phase compensator of the present invention having the above configuration is as follows. In the process of signal processing, a phase error occurs in which the image signal sampling clock does not coincide with the sample point due to group delay caused by different HD frequencies for reproducing the image signal and the receiver control clock. In addition, due to the overshoot and undershoot of the HD waveform as shown in FIG. 2, an error occurs in the phase detection and the comparison value, thereby making it impossible to purify the phase detection. That is, in FIG. 2, the phase detection and comparison value are determined by the value of (P1 + P3) / 2-P2.

Therefore, in the present invention, the phase error between the clock and the image signal generated by the group delay and the distortion of the HD waveforms is determined by the transmission system phase adjusting unit 170 and the non-transmission system phase compensator 180 for the transmission system and the non-transmission system, respectively. By controlling and adjusting the phase error by fine adjustment, the overall error is converted into an analog value by the D / A converter 130. The loop filter 140 smoothes the output of the D / A converter 130 and applies the voltage controlled oscillator 150 to the A / D converter 60 with the frequency generated from the voltage controlled oscillator 150 being phase compensated. ) To A / D conversion of image data. That is, as described above with reference to FIG. 3, the values of P1, P2, and P3 of the HD waveform of FIG. 2 are output by the four flip-flops 111-114 of the time window 110. The P3 value is input at the input terminal, the value of P2 is output at the output terminal of the flip-flop 114, and the value of P1 is output at the output terminal of the flip-flop 114.

Accordingly, the phase detection and comparison unit 120 of FIG. 3 performs the (P1 + P3) 2-P2 operation to detect the comparison signal. The comparison signal is actually output as a value having an error due to overshoot and undershoot. In other words, if the phase between the image input signal and the voltage controlled oscillator does not exactly match, the values of P1, P2, and P3 do not have 64,128,192 levels, and output signals to the point A that are out of phase.

Therefore, at the point A, a correction signal corresponding to the data values of the phase correction units 170 and 180 is applied through the A / D converter 121 to output the corrected data to the D / A converter 130.

By taking the data sampled cleanly by the A / D converter 60 by the frequency output from the voltage controlled oscillator 150 by the corrected data as described above, it is possible to faithfully reproduce the vivid image and color.

Meanwhile, the present invention includes an input processing control unit 70 for controlling diseases of transmission and non-transmission signals so as to control the multiplexers 30 and 160. That is, a high definition TV has a high frequency of use and transmits satellites, cables, or UHF. By transmitting the sample value, the installation location and characteristics of the receiver set are phase-corrected according to the data of the field system phase correction unit 170, so that faithful color can be output without ringing to a reproduced image such as a high-definition VTR or a video disc. If the reception does not change, one adjustment is unnecessary.

According to the automatic phase compensator of the present invention as described above, the generated re-sampling clock generates sub-sampling, thereby minimizing image degradation and simultaneously switching the inputs according to the input signal sources of transmission and non-transmission systems. And phase correction data switching is automatically performed.

Claims (2)

A high-definition television receiving system including a receiver (10), a de-emphasis circuit (20), an amplifier (40), a low pass filter (50), and an A / D converter (60), wherein the A / D converter (60). A phase detection and comparison unit 120 for detecting a phase by the output of the time window 110 configured at an output terminal of the phase correction unit and correcting a phase error by the input data of the phase correction unit, and the phase detection and comparison unit 120 A voltage controlled oscillator 150 generating a control frequency of the A / D converter 60 by inputting the output of the loop filter 140 and the D / A converter 130 and the smoothing loop filter 140 configured at the output terminal. Auto phase compensator for high-definition TV characterized by comprising a closed loop. [4] The automatic phase compensator for high-definition TV according to claim 1, wherein the phase correction data input to the phase detection and comparison unit 120 is configured to automatically switch the data according to the transmission system and the non-transmission system.

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