Apparatus and method to derive a television color subcarrier frequency signal from a computer video signal

• Main Authors: ZHANG, SUNNY Y, LIN, JUSTIN J
• Format: Patent
• Language: English; French; German
• Published: 28.10.1998
• Edition: 6
• Subjects: ADVERTISING; ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICESUSING STATIC MEANS TO PRESENT VARIABLE INFORMATION; CRYPTOGRAPHY; DISPLAY; EDUCATION; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PHYSICS; PICTORIAL COMMUNICATION, e.g. TELEVISION; SEALS

The subcarrier generator is connected between a digital encoder and a computer which generates a horizontal sync signal. The apparatus includes a frequency conversion circuit, pref. a phase locked loop, which generates a pixel clock signal from the computer horizontal sync signal. A clock device generates a reference clock signal and a deviation compensator processes this signal, along with the pixel clock signal to derive a subcarrier relative phase signal. The relative phase signal is then used to generate the television subcarrier signal. Pref. the deviation compensator includes a signal comparison circuit consisting of a timer which is activated for a period of time established by the pixel clock signal, and a counter which counts transition cycles in the reference clock signal. In addition, the counter is activated by control logic in order to provide selection signals to a multiplexer which reads the cycle count signal from the counter.