| 摘要 |
A sync vector generator for a composite vectorscope generates a gate from the horizontal sync pulses of a video input signal as a function of a reference signal selected from either the video input signal or an external reference signal. The gate width is equal to an integer multiple of cycles of the subcarrier frequency for the video input signal. A high-Q resonant tank circuit tuned to the subcarrier frequency is activated by the gate to produce a burst signal having a frequency equal to the subcarrier frequency and having a number of cycles equal to the integer multiple. The burst signal is input together with quadrature subcarrier frequency components to the demodulators of a conventional vectorscope to produce an output display that is a measure of horizontal sync jitter and instantaneous SC/H phase.
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