AWR1642: Antenna coupling signature and its compensation algorithm in mmw demo

Hi Adam

Antenna coupling is the direct coupling of the Tx antenna signals to the Rx antenna. In the output spectrum it would look like a strong reflector close to DC (or the 0th range bin). A strong antenna coupling signature can 'drown' out the reflected signals from weak reflectors - (for e.g, if you place your hand about 5cm from the device, it may not get detected).

Antenna coupling would depend on the isolation between the Rx antennas and the Tx antennas. But it would be a stable signature for a given chirp configuration. So we can measure it, and remove it.

The calibDcRangeSig option simply computes the average chirp (after 1D FFT for a couple of frames) and then subtracts a portion of it from 'every' chirp henceforth. In other words, we estimate the mean signature of the scene and remove it from every measurement afterwards.

This can help in the case of antenna coupling, because, we know that Antenna coupling is a stable signature, and occurs only very close to the radar. So we use the calibDcRangeSig option to estimate the average chirp, and then remove the stable signature from the first few range bins.

Regards
Anil