Re: Quasi-Synchronous Demodulation
I never worked on TV demodulators, but from what I recall, there are several factors which need to be simultaneously addressed, and one of some importance (esp. in the early days of UHF TV Rx's) was phase-noise.
If you construct an "ideal" synchronous demodulator, and the incoming IF has significant LF phase-noise (predominantly from the UHF tuner's low-cost VCO), the side chain should ideally track the phase-perturbations to avoid pm- to-am conversion. I think a quasi-synchronous demod with a not-too-high Q meets this criteria, in that LF phase-noise is effectively tracked, but HF (e.g chroma and sound carriers) are not.
John
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