I'm using an AD8302 to measur phase and magnitude beteewn to signals in the frequency range from 1MHz to 50MHz.
I've tested with two -30dBm signals and variable phase difference and same frequency (10 MHz). Also used test with two signals 1kHz as sugested somewhere else in this forum. Can only get an output Vphs voltage from 0.7V to 1.2V for a 180º to 0º variation ( instead of 0V to 1.8V, so no 10mV/degree slope). Tested with two AD8302 pieces with similar results. Magnitude output seems OK.
Capacitors used on pins INPA,OFSA,VPOS,OFSB AND INPB are 100nF, capacitors on pins MFLT and PFLT are 10nF.