System and method for automatically controlling the phase of a clock signal for sampling an HDTV signal
View Patent ↗The present invention provides a system and method for automatically controlling the phase of the clock signal for sampling an HDTV signal, which implements a new and improved method for phase detection. The system and method utilize the standard format of an HDTV signal to consistently ensure accurate phase detection. Particularly, the system and method detect the target phase for the sampling clock using a tri-level sync pattern that exists at the beginning of each display line. This tri-level sync pattern or “sync pulse” is well suited for phase detection since it includes several static areas separated by substantial transitions. Furthermore, by using the sync pulse of the HDTV signal, the system and method provide consistent and accurate results, since the sync pulse will not change regardless of the whether the video data is static or in motion.
1. A method for detecting a phase of a clock signal for sampling an HDTV signal, comprising:
detecting a sync pulse of the HDTV signal; and
selecting a phase for the clock signal by applying a phase detection process to the sync pulse that results in sampling the sync pulse in a stable region.
2. The method of claim 1 further comprising:
digitizing the HDTV signal.
3. The method of claim 1 wherein the sync pulse comprises a tri-level sync pulse.
4. The method of claim 1 wherein the HDTV signal is an interlaced signal.
5. The method of claim 4 wherein the HDTV signal is a 1080i signal.
6. The method of claim 1 wherein the HDTV signal is a progressive signal.
7. The method of claim 6 wherein the HDTV signal is a 720p signal.
8. The system of claim 1 wherein the HDTV signal is an interlaced signal.
9. The system of claim 8 wherein the HDTV signal is a 1080i signal.
10. A system for detecting a phase of a clock signal for sampling an HDTV signal, comprising:
a circuit that detects a sync pulse of the HDTV signal, and selects a phase for the clock signal by applying a phase detection process to the sync pulse that results in sampling the sync pulse in a stable region.
11. The system of claim 10 wherein the circuit detects the sync pulse using a digitized HDTV signal.
12. The system of claim 11 further comprising:
a phase-locked loop that provides the clock signal; and
a controller that is coupled to the phase-locked loop and to the circuit, the controller being adapted to instruct the phase-locked loop to provide the clock signal at the selected phase based on information received from the circuit.
13. The system of claim 12 further comprising:
a sync separator that is coupled to the phase-locked loop, that separates sync data from the HDTV signal and that communicates the sync data to the phase-locked loop, which uses the sync data to provide the phase of the clock signal.
14. The system of claim 13 further comprising:
a mode detection circuit that is adapted to determine a frequency for the clock signal.
15. The system of claim 10 wherein the sync pulse comprises a tri-level sync pulse.
16. The system of claim 10 wherein the HDTV signal is a progressive signal.
17. The system of claim 16 wherein the HDTV signal is a 720p signal.
18. A display device comprising:
a display monitor for displaying images provided by an HDTV video source;
an A/D converter that is communicatively coupled to the display monitor, and that uses a clock signal to convert an analog input signal from the HDTV video source into a first digital signal that is used by the display monitor to display images;
a phase-locked loop that is communicatively coupled to the A/D converter and that provides the clock signal to the A/D converter;
a phase detection circuit that receives the first digital signal and that determines a target phase for the clock signal by detecting a sync pulse of the first digital signal, and selecting a phase for the clock signal by applying a phase detection process to the sync pulse that results in sampling the sync pulse in a stable region; and
a controller that is communicatively coupled to the phase detection circuit and to the phase-locked loop, the controller being adapted to instruct the phase-locked loop to provide the clock signal at the target phase based on information received from the circuit.
19. The display device of claim 18 further comprising:
processing circuitry that is communicatively coupled to the A/D converter and that is adapted to process the digital signal before communicating the digital signal to the display monitor.
20. The display device of claim 19 wherein the processing circuitry comprises a scaling circuit.
21. The display device of claim 20 further comprising:
driver circuitry that is communicatively coupled to the processing circuitry and to the display monitor, and that is adapted to drive the display monitor based on a processed digital signal received from the processing circuitry.
22. The display device of claim 21 wherein the signal from the HDTV video source comprises an interlaced signal, and wherein the processing circuitry further comprises a de-interlacing circuit.
23. The display device of claim 21 wherein the signal from the HDTV video source comprises a progressive signal.
24. The display device of claim 18 wherein the sync pulse comprises a tri-level sync pulse.
25. The display device of claim 21 further comprising:
a sync separator that is coupled to the phase-locked loop, that separates sync data from the signal from the HDTV video source and, that communicates the sync data to the phase-locked loop, which uses the sync data to provide the phase of the clock signal.
26. The display device of claim 18 further comprising:
a mode detection circuit that is adapted to determine a frequency for the clock signal.