The following note was found on page 252 of UG-992. "Design the RF line systems between the device ball pad reference plane and the balun/filter reference plane for a differential impedance (ZDIFF) of 100 Ω for the receivers and 50 Ω for the transmitters. This is a compromise impedance with respect to frequency and a good starting point for design."

Why would the differential impedance of the receivers be different than the transmitters? We are laying out a wide band development board similar to the ADRV-9371W and i would like to make sure we get this right. I would think both the Rx and Tx would be 100 ohms differential, 50 ohms to ground?

AD9371 has different Transmitter and Receiver RF port Impedance and varies across the frequency as well.

Refer to Transmitter Impedance Matching Network Design Methodology and General Receiver Impedance Matching Network Design Methodology from UG-992.

You shall download the S-Parameter file from below link and design your own matching network to meet your frequency of application

SDR Integrated Transceiver Design Resources | Analog Devices