[amsat-bb] Modulating UHF Retro Reflector at RF?
ross at topwire.co.nz
Tue Aug 9 08:50:37 UTC 2016
Years ago I built a "moving target simulator" for a K-band CW (homodyne)
radar. I simply took the Gunnplexer module out of a K-band automatic
door opener (a 24.125 GHz resonant cavity complete with feed horn, Gunn
diode local oscillator and RX mixer diode) and fed my simulated doppler
AF signal into it's RX mixer diode (I did not energise the Gunn diode -
so the microwave oscillator was NOT operating).
When I illuminated it with 24 GHz RF from the radar, it produced good
reflections at RF + AF and RF - AF. I did not have access to good K-band
microwave test equipment so I was unable to quantify the strength of the
reflections or mixing conversion loss, etc.
So I would say that yes, subject to sufficient link budget, if you had
an antenna in orbit, coupled to a mixer diode, and you drove that mixer
diode with AF modulation, then that antenna will re-radiate the mixing
products of the RF illumination and AF modulation. Would this be an
interesting experiment for an ulta-low-power bird that does not have the
power budget to run an RF transmitter?
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