Filtering signals with non-uniform sampling rate (staggered PRF)

There is an example Ground Clutter Mitigation with Moving Target Indication (MTI) Radar for Phased Array Toolbox. There is used staggered PRF for Doppler ground clutter filtering. And there is somehow calculated such filtering frequency response:

% Calculate the magnitude frequency response for the three-pulse canceller
pf1 = @(f)(1-2*exp(1j*2*pi/prf(1)*f)+exp(1j*2*pi/prf(2)*f));
pf2 = @(f)(1-2*exp(1j*2*pi/prf(2)*f)+exp(1j*2*pi/prf(1)*f));
sfq = (abs(pf1(f)).^2 + abs(pf2(f)).^2)/2;

Cannot you tell me, how was it done? What should I read to understand, how the formula was made?

Answer 1

[Honglei Chen]

The idea is that the total filter response is the combination of the two individual pulse cancellers. The equation actually plots the power response instead of the magnitude response. The factor of 2 is there to preserve the power. This being said, the subscript may have been messed up in the last term of the two equations. I just tried switching the two indices and even though the result is different, the shape is approximately the same, i.e., only one null across all frequencies.

HTH