Agc detector and method for agc detecting

• US 20050088367A1
• Filed: 02/03/2003
• Published: 04/28/2005
• Est. Priority Date: 02/09/2002
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Zupke, Manfred, Kuhn, Hans-Jurgen
• Granted Patent: US 7,259,799 B2
• Time in Patent Office: Days
• US Class Current: 345/10
• CPC Class Codes: H04N 5/53 Keyed automatic gain control

Abstract

Disclosed is an AGC detector device and an AGC detecting method for television receivers displaying video pictures consisting of a plurality of horizontal lines to be built up successively, wherein a CVBS signal is inputted which includes horizontal sync pulses having a front porch region and a back porch region and occurring once a horizontal line during a horizontal sync period when generating a current video picture, and further includes vertical sync pulses occurring during a vertical sync period before the generation of a new video picture and including serration pulses which occur during a serration pulse region being part of the vertical sync period. Further, gating pulses are generated having a period which is equal to the line period of the horizontal sync pulses. Said gating pulses are adjusted such that they occur at the back porch region of the horizontal sync pulses. The particularity of the invention is that the occurrence of the gating pulses is shifted during the serration pulse region of the vertical sync period so that the gating pulses occur earlier by a time interval corresponding to the time distance between a front porch region and the next back porch region or later by a time interval corresponding to the time distance between a back porch region and the next front porch region.

Claims

1. An AGC (automatic gain control) detector device for television receivers displaying video pictures consisting of a plurality of horizontal lines to be built up successively, comprising

means (2) for inputting a CVBS (color video blanking sync) signal which includes horizontal sync pulses having a front porch region and a back porch region and occurring once a horizontal line during a horizontal sync period when generating a current video picture, and further includes vertical sync pulses occurring during a vertical sync period before the generation of a new video picture and including serration pulses which occur during a serration pulse region being part of the vertical sync period,

means (10) for generating gating pulses having a period which is equal to the line period of the horizontal sync pulses, and

means (10) for adjusting said gating pulses such that they occur at the back porch region (Δ

T1) relative to the horizontal sync pulses, characterized by

means (10) for shifting the occurrence of said gating pulses during the serration pulse region of the vertical sync period so that the gating pulses occur earlier by a time interval corresponding to the time distance (Δ

T1+Δ

T2) between a front porch region and the next back porch region or later by a time interval corresponding to the time distance (Δ

T3−

Δ

T1) between a back porch region and the next front porch region.

2. The device according to claim 1, further characterized by

first means (10) for detecting the occurrence of the back porch region of the horizontal sync pulses, and

second means (10) for detecting the occurrence of the front porch region of the horizontal sync pulses,

wherein said first and second detecting means (10) are coupled to said shifting means (10), and at least said first detecting means (10) is coupled to said adjusting means (10).

3. The device according to claim 1 or 2, characterized in that the device (10) is a digital AGC detector device.

4. The device according to at least any one of claims 1 to 3, characterized in that the device (10) is provided for analog television receivers.

5. The device according to at least any one of claims 1 to 4, wherein said gating pulses generating means (10) comprises a PLL circuit.

6. The device according to claim 5, wherein said PLL circuit is a H-PLL circuit, and said gating pulses generating means (10) further comprises a V-INTEGRATOR.

7. The device according to at least any one of claims 1 to 6, wherein said gating pulses generating means (10) comprises a sync slicer.

8. A method for AGC (automatic gain control) detecting for television receivers displaying video pictures consisting of a plurality of horizontal lines to be built up successively, comprising the steps of

inputting a CVBS (color video blank sync) signal which includes horizontal sync pulses having a front porch region and a back porch region and occurring once a horizontal line during a horizontal sync period when generating a current video picture, and further includes vertical sync pulses occurring during a vertical sync period before the generation of a new video picture and including serration pulses which occur during a serration pulse region being part of the vertical sync period,

generating gating pulses having a period which is equal to the line period of the horizontal sync pulses, and

adjusting said gating pulses such that they occur at the back porch region (Δ

T1) relative to the horizontal sync pulses, characterized by the further step of

shifting the occurrence of said gating pulses during the serration pulse region of the vertical sync period so that the gating pulses occur earlier by a time interval corresponding to the time distance (Δ

T1+Δ

T2) between a front porch region and the next back porch region or later by a time interval corresponding to the time distance (Δ

T3−

Δ

T1) between a back porch region and the next front porch region.

9. The method according to claim 8, characterized in that at least the step of shifting the occurrence of said gating pulses during the serration pulse region is carried out in the digital domain.

10. The method according to claim 8 or 9, characterized in that the method is provided for analog television reception.