as you can see on the following schematic my ADL5906ACPZ#1428 is the very similar configuration like it is on the evaluation Board.
Without an input signal I have an output voltage of 1V to 1,4V. (vary with the ADL5906 IC)
Even if I connect the RFIN+ pin via 10nF capacitor to ground I have an output voltage 1V+
In comparison the evaluation board has an output voltage of 0.05V without an input signal.
With this issue I am not able to detect any signals < -45dBm at 2Ghz.