FMCW - FFT - Range resolution

Question

with a prototype of FMCW radar I'm trying to resolve the distance to the target

The Audio card characteristics are as follows: Fs= 44100Hz

So the FMCW radar range resolution is RR=440MHz/c = 0.34m Ts=20ms thus, number of points N=Fs*Ts = 882

I've tried putting the target on various distances 1m, 1.1m, 1.2m, 1.3m all the way to 2m

Does the range resolution limit me from calculating distance changes of 0.1m? I'm new to this and would appreciate your help.

My code takes the IF difference, Does FFT of the signal with 4*N points (I don't know why but this just worked whilst testing) I get the correct distances but my question is How?! Do targets not have to be spaces 34cm apart ?

When I produce the plot (X axis is 0 to max_range which is around 150m with the given data, and Y axis is the FFT values with 4*N samples.

Could someone point me in the right direction?

Answer 1

If your IF frequency is TOO LOW, will the Doppler Information still be present?

And to watch the Doppler Frequency change, you need enough samples, to have enough bins, to observe the Carrier shifting between bins.