We have tried to measure the phase noise of RFX900 daughter board when the daughter board is mounted on a USRP 1 mother board. When we directly connect the TX/RX port to the RX2 port through a 46dB attenuation signal, we still observe significant amount of phase noise as shown in the attached figures. Those figures suggest that the phase noise is about 8 degrees which cannot be tolerated by many communication systems. Would be great if you guys can provide some suggestions on reducing the phase of the USRP platform.
Pengyu
