[hpsdr] Cyclops ideas

[David McQuate]

(6)  Image-reject mixing--
   (a) The ADF4351 operates to 4.4 GHz.  Take the output & feed a pair 
of (probably GaAs) flip-flops, generating a quadrature pair.  Use those 
with a pair of mixers, forming an image-reject mixer.  At least for this 
smaller frequency range images are greatly reduced.

   (b) The ADF4351 has two sets of differential VCO outputs.  Use two of 
these chips.  Use outputs A in an image-reject mixer topology.  Connect 
outputs B to a simple mixer, used as a phase detector, and sum the 
output of this mixer with that from one of the ADF4351s to its VCO tune 
line.  This addition would be low bandwidth, with the aim of locking the 
two ADF4351s in quadrature.  The output of this third mixer will be zero 
volts when the two are in quadrature (plus some noise due to the two 
VCO's phase noise.)   The two may not be in perfect quadrature, so the 
image cancellation may not be perfect, but maybe we could get 10 dB? 15?

73,
Dave
wa8ywq

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