Steve:
If I understand your question - is there any sort of high pass filter inside the Rx path - no.
iio-oscilloscope/fmcomms2.svg at master · analogdevicesinc/iio-oscilloscope · GitHub
There is no AC coupling between the LNA and ADC. If you tune the Rx LO for 2.40000 GHz and receive a tone at 2.40000 GHz, you will see a "DC" tone in your FFT.
-Robin