This seems too hokey to me. Just use the AD829 and the switching techniques that are in the Sigg electronics. Using this relay/LF crap will leave us with a lot of phase lag. The board should have less than 10 deg. of phase lag at 300 kHz.

1) For the regulators, you should use bigger caps in parallel with the little caps. Big means > 50 uF.

2) Since this is quasi generic, you ought to have more pads around the input opamp and some of the others. Look at the layout of the generic stages in the Sigg MC board.

3) For the RF, we don't want to put the PD signal through a noisy phase shifter. The LO signal shoudl be the one getting phase shifted.