One of my 1st designs was replacing ground based Radar with Doppler using OCXO +PLL to 100kHz sub-carrier FM pilot tone on Tx, then received and mixed with same OCXO ( using PLL to scale to same 10MHz) to get change in RANGE and azimuth shift with 2 antenna. It worked very well since my design was stable to 1e-10 for rocket harsh environment of 100g shock, 50g accel, and 15g vibe.
Range is phase of 1 cycle at speed of light and velocity is d (phi) /dt so counting cycles determines total range.
I used an analog sawtooth mixer so the result was an analog linear phase shift with range. It worked very well and the error frequency was nulled before launch. Circa 1976
The resulting out waveform was an exact duplicate of the sawtooth due to my method of precise very fast S&H such that if each transition of the sawtooth were used to accumulate instead , you would see the precise parabolic path of the rocket as perceived by the apparent tangent distance called "Range" and this can see the peak apparent altitude ( just after Apogee) and thus the mixed output sawtooth slows to a zero ramp 0 f. or DC then changes direction or slope coming down to earth. In our case Apogee was over 500 miles for plasma research.:bsdetector: