DIGITIZED ANALOG TV SIGNAL PROCESSING SYSTEM

• US 20090273714A1
• Filed: 04/30/2008
• Published: 11/05/2009
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Xueshan Technologies Inc. (Wi-LAN Inc.)
• Original Assignee: MediaTek, Inc.
• Inventors: Liou, Ming-Luen, Chen, Yi-Fu, Lin, Ray-Kuo
• Granted Patent: US 8,212,941 B2
• Time in Patent Office: Days
• US Class Current: 348/572
• CPC Class Codes: H04N 21/42638 involving a hybrid front-end, e.g. analog and digital tuners
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 5/148 Video amplifiers amplifiers in general H03F
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response
• CPC Class Codes: H04N 5/205 for correcting amplitude versus frequency characteristic
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
• CPC Class Codes: H04N 5/213 Circuitry for suppressing or minimising impulsive noise for suppressing or minimising disturbance in image signal generation H04N23/81
• CPC Class Codes: H04N 5/4446 IF amplifier circuits specially adapted for B&W TV RF amplifiers in general H03F3/189
• CPC Class Codes: H04N 5/455 Demodulation-circuits
• CPC Class Codes: H04N 5/46 for receiving on more than one standard at will deflecting circuits of multi-standard receivers H04N3/27
• CPC Class Codes: H04N 5/52 Automatic gain control
• CPC Class Codes: H04N 5/60 for the sound signals
• CPC Class Codes: H04N 5/62 Intercarrier circuits, i.e. heterodyning sound and vision carriers H04N5/607 takes precedence

Abstract

A digitized analog television signal processing system is disclosed, comprising an analog-to-digital converter, a demodulation unit, a decoding unit, and a control unit. The analog-to-digital converter samples a television signal comprising a video signal. The demodulation unit demodulates the video signal. The decoding unit decodes the demodulated video signal. The control unit adjusts the demodulation unit according to a signal quality indicator generated during and/or after the decoding of the decoding unit.

Claims

1. A digitized analog television signal processing system, comprising:

an analog-to-digital converter configured to sample a television signal comprising a video signal;

a demodulation unit configured to demodulate the video signal;

a decoding unit configured to decode the demodulated video signal; and

a control unit configured to adjust the demodulation unit according to a signal quality indicator generated during and/or after the decoding of the decoding unit.

2. The digitized analog television signal processing system as claimed in claim 1, wherein the television signal further comprises a sound signal, the digitized analog television signal processing system further comprises a sound processing unit configured to demodulate and/or decode the sound signal, the signal quality indicator is further generated during and/or after the processing of the sound processing unit.

3. The digitized analog television signal processing system as claimed in claim 2, wherein the demodulation unit comprises a filter bank configured to separate the video signal and the sound signal from the television signal.

4. The digitized analog television signal processing system as claimed in claim 3, wherein the signal quality indicator comprises a signal-to-noise ratio (SNR) of the video signal, the control unit is configured to make a bandwidth of the filter bank reduced when the SNR is lower than a threshold.

5. The digitized analog television signal processing system as claimed in claim 3, wherein when the signal quality indicator indicates that a sound carrier of the sound signal is different from a presumed sound carrier, the control unit is configured to make a passband center of the filter bank shifted from the presumed sound carrier to the sound carrier.

6. The digitized analog television signal processing system as claimed in claim 3, wherein the signal quality indicator comprises a signal-to-noise ratio (SNR) of the sound signal, the control unit is configured to make the filter bank suppress the video signal or an adjacent channel interference when the SNR is lower than a threshold.

7. The digitized analog television signal processing system as claimed in claim 1, wherein the demodulation unit demodulates the video signal according to a first standard type, when the signal quality indicator indicates that the decoded video signal is unrecognizable, the control unit is configured to make the demodulation unit demodulate the video signal according to a second standard type.

8. The digitized analog television signal processing system as claimed in claim 2, wherein the analog-to-digital converter samples the television signal at a first sampling rate, and the control unit is configured to make the analog-to-digital converter sample the television signal at a second sampling rate when the signal quality indicator indicates that the video signal or the sound signal has been interfered by an adjacent channel interference signal.

9. The digitized analog television signal processing system as claimed in claim 1, wherein the demodulation unit further comprises a carrier recovery unit configured to lock a video carrier of the video signal at an intermediate frequency, and the control unit is configured to make a loop bandwidth of the carrier recovery unit controlled according to the signal quality indicator.

10. The digitized analog television signal processing system as claimed in claim 9, wherein the signal quality indicator comprises a signal-to-noise ratio (SNR) of the video signal, the control unit is configured to make the loop bandwidth of the carrier recovery unit reduced when the SNR is lower than a threshold.

11. The digitized analog television signal processing system as claimed in claim 9, wherein when the signal quality indicator indicates that the video carrier is not locked at the intermediate frequency, the control unit is configured to make parameters of the carrier recovery unit reset.

12. The digitized analog television signal processing system as claimed in claim 1, wherein the demodulation unit comprises an equalizer configured to shape a frequency response of the television signal, and the control unit is configured to control the equalizer according to the signal quality indicator.

13. The digitized analog television signal processing system as claimed in claim 12, wherein the signal quality indicator comprises a signal-to-noise ratio (SNR) of the video signal, and the control unit is configured to make the equalizer reject a high-frequency noise when the SNR is lower than a threshold.

14. The digitized analog television signal processing system as claimed in claim 12, wherein when the signal quality indicator indicates an energy imbalance between a luminance signal and a chrominance signal of the television signal, the control unit is configured to make the equalizer compensate for the energy imbalance.

15. The digitized analog television signal processing system as claimed in claim 12, wherein when the signal quality indicator indicates a group delay between a luminance signal and a chrominance signal of the television signal, the control unit is configured to make the equalizer compensate for the group delay.

16. The digitized analog television signal processing system as claimed in claim 12, wherein when the signal quality indicator indicates a waveform overshoot of the television signal, the control unit is configured to make the equalizer reduce the waveform overshoot.

17. The digitized analog television signal processing system as claimed in claim 1, wherein the demodulation unit comprises an automatic gain controller configured to control a dynamic range of the television signal, and the control unit is configured to control a loop tuning speed of the automatic gain controller according to the signal quality indicator.

18. The digitized analog television signal processing system as claimed in claim 17, wherein the signal quality indicator comprises a signal-to-noise ratio (SNR) of the video signal, and the control unit is configured to make the automatic gain controller reduce the loop tuning speed of the automatic gain controller when the SNR is lower than a threshold.

19. The digitized analog television signal processing system as claimed in claim 17, wherein when the signal quality indicator indicates that a signal level of a reference signal of the television signal is different from a standard signal level, the control unit is configured to make the automatic gain controller modify the signal level of the reference signal to the standard signal level.

20. The digitized analog television signal processing system as claimed in claim 17, wherein the demodulation unit further comprises a carrier recovery unit configured to lock a video carrier of the video signal at an intermediate frequency, and the control unit is configured to control a loop bandwidth of the carrier recovery unit according to the signal quality indicator.

21. The digitized analog television signal processing system as claimed in claim 1, wherein the signal quality indicator is further generated during and/or the demodulation of the demodulation unit, the control unit is further configured to adjust the decoding unit according to the signal quality indicator.