For the receiver section of the AD9361: Is the IF signal path between the IF output of each mixer and the input of each ADC DC-coupled? Thanks.
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.
It is DC coupled.
Many thanks to rgetz and tlili for your answers.
We're just beginning to learn the AD9361 and it behaves as if it was AC-coupled (highpass) between the mixer IF output and the ADC input. An FFT of a CW carrier input nulls down to about -40 dB and the I and Q time-domain waveforms decrease to essentially zero as the RF input CW frequency approaches and then equals the AD9361 LO frequency (718 MHz). Any ideas?
BB DC offset tracking calibration is implemented as a loop resulting in a high pass frequency response.
If your waveform has DC content or content at low frequencies we recommend turning off BB DC offset tracking calibration algorithm.
Thank you for your suggestion. We'll give it a try. Steve
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