US 4,729,011 AGranted

Method and apparatus for digitizing television signals

AssigneeU.S. Philips Corporation

InventorKenneth D. McCann

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Abstract

An arrangement for digitizing television signals, particularly the staircase portion of the vertical interval test signal transmitted by the British Broadcasting Corporation and the Independent Broadcasting Authority comprises a luminance/chrominance separator (2) and two analog to digital converters (ADC's) (6, 9). The ADC(6) digitizes the color subcarrier which has a low amplitude but a high frequency while the ADC(9) digitizes the high amplitude low frequency luminance portion. The digitized samples are stored in two sections of RAM (11, 13) under the control of a write address generator (25) and two respective write control circuits (14,17). The ADC(6) operates at 4.sub.fsc and has a resolution of 7 bits while the ADC(9) operates at one sixteenth of that rate and has a resolution of 10 bits. This enables a full 10 bit resolution to be obtained without requiring a high cost ADC.

Claims13

Dependent claims

A television transmitter comprising a video signal input;

means for modulating a carrier signal by the video signal;
non-linear power amplifier means for amplifying the modulated carrier signal;
a pre-corrector circuit for applying a correction to the video signal before or after modulation and before it is applied to the power amplifier means, means for measuring the distortion in the output of the power amplifying means;
means for generating a control signal representative of the distortion of the output of the power amplifying means;
and means for applying the control signal to a control input of the pre-corrector circuit to reduce the distortion at the output of the power amplifying means;
wherein the measuring means comprises means for extracting a portion of the transmitted signal, and means for demodulating the portion to produce a demodulated television signal, wherein the measuring means further comprises means for digitizing the demodulated television signal, the digitizing means comprising means for separating said luminance and color subcarrier portions, means for applying the separated luminance portion to a first analog-to-digital converter, and means for applying the separated color subcarrier portion to a second analog-to-digital converter having a lower resolution and a higher speed of operation than said first analog-to-digital converter.

3 more elements

Dependencies are inferred from the claim text.