AD8302 EVALUATION BOARD: Linearity error on phase output measurement Vphs
I tested the board with the following setup: RF generator set at 352MHz and output signal applied on INPA and INPB, via a balanced splitter. Input level set at # -20dBm on both inputs. Phase is adjusted with a mechanical phase shifter inserted on INPB side. Phase between the 2 signals is recorded with a vector voltmeter type HP8508 (measurement pickup done with directional couplers inserted on each input). Swith SW2 is positioned in phase measure mode. The output Vphs is connected to a DVM. When Phase difference is set at 0° between the 2 RF signals, the DVM displays 1.905V and not the 1.8V (or less) specified on the notes. I made several measurement points between 0 and ±180° and I found the linearity not good: gap larger than ±1°, except around +90° and -90°. I agree that there is an important drift at extreme values 0° and ±180°, but between, the values should be less than ±1° at 352MHz according to the specified graphs.
As anyone done this phase measurement on the AD8302 evaluation board and got better results on Vphs output?
My whole results are recorded on the attach excel file.