I am emitting ultrasound with a speaker and am trying to track moving objects with a microphone array by detecting doppler shifts. I have succeeded to detect movement. However, to detect the direction of the movement, I found that I need to cancel the sounds reflected from the stationary objects. The goal is similar to MTI filters in aircraft radars which used for clutter filtering.
Consider input signal 1 (Sig1 for short) caused by movements (i.e., contains doppler shift) and input signal 2 (Sig2 for short) reflected from stationary objects. I have first simply tried subtracting the frequency spectra of Sig1 with Sig2 but did not work well. Furthermore, I tried to simply filter the non-doppler shift related frequencies by setting them to zero. This removes reflected sounds to a certain degree but still contains reflected sounds sources. Is there a robust way I can make use of?
I am relatively new to this area. Thank you for your help in advance.