On 6/17/15 6:15 PM, John Miles wrote:
Also see http://www.ke5fx.com/gunnpll.html , a quick and dirty but
successful attempt at locking a Gunnplexer in a relatively low (1
kHz) loop bandwidth. The inband noise is likely too high for good
performance in a radar application, but the basic idea is workable
enough. Unfortunately I tried this experiment before I had any way
to generate log plots. :(
I can't think of many noise-critical applications where a microwave
VCO is used without some form of phase locking. I'd think that a
homodyne architecture would still need a synthesized source, just
because the waveform being received is delayed relative to the one
that was sent.
Yeah, but at short ranges (<100m) that delay is on the order of <1
microsecond. So low frequency phase/frequency variations cancel
themselves out.
Police radar speed detectors are a fine example. Gunn oscillators work
just fine here when operated open loop.
Without a clean source, I'd imagine that you'd have
to do autocorrelation between the outgoing and incoming channels
rather than simple/cheap baseband mixing. An obvious question would
be whether it's cheaper to add another digitizer and correlator to
your pipeline than it would be to clean up your source...
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