The data sheet shows common-mode rejection ratio on page 14, figure 24 as 57 dB at 1GHz.
Using the s-parameters given for the device shows a common mode gain of approx -32 dB in the 6 dB gain configuration at 1GHz. The same simulation shows approx. 6 dB of differential gain, so I believe the simulation is set-up correctly.
How was the common-mode rejection ratio measured? Can I expect CMRR around 57 dB at 1GHz? I will be using the device in a circuit that will have a significant common-mode RF signal that I want to reject.