No, no, no, it's not that bad :-) I should not post here in the middle
of the night. Sorry to cause that confusion.
Minimum is -90 dBc @ 50 Hz, or let's say @100 Hz @ 10 GHz.
that would equal -110 dBc@1 GHz, or -130 dBc @100 MHz, BTDT.
And then, the ~4 MHz difference between TX and RX frequency could be
done by a SSB mixer with a non-multiplied crystal. We would have some
common mode noise, but the RX-TX difference would be fairly constant.
It would not de-correlate over the 10 mm run length, not at low
offsets where it counts.
The -110 was only meant for "Don't care about multiplied white noise
floor", not in the sense of a spec but in the sense of "guaranteed
harmless". It's not such a great relaxation after all, it could be
20 dB looser.
The question was really only about a _simple_ multiplier chain. The
style used in ham radio 10 GHz transverters has too many stages,
GaAS-Fets with 1/f and pipe cap filters. Too complicated.
Macom still make a SRD diode, but probably it is easiest to phaselock
a ceramic puck or an on-chip VCO to a 100+ MHz crystal. The offset-
mixing removes the need for a low reference frequency or fractional
voodoo.
cheers, Gerhard
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