Sample data phase locked loop for adaptive doppler tracker

Claim 1

In a communications system a digital adaptive doppler tracker operating in response to system control signals, said adaptive doppler tracker including a sample data phase locked loop, said sample data phase locked loop comprising rectangular to polar coordinate conversion means receiving digitized bipolar X, Y inphase and quadrature input signals and outputting polar digital signals R, φ, subtractor means subtracting a phase estimate signal φ from said phase signal φ to provide a phase error signal φ E , a coherence estimate loop receiving said phase error signal φ E and providing the coherence function, C.sub.(i+1) =C.sub.(i) -f(φ E ), f (φ E ) being a function of phase error., said coherence estimate loop developing a bandwidth control output signal, a frequency estimate loop receiving said phase error signal φ E and said bandwidth control signal and providing the frequency function, F.sub.(i+1) =φ E (i) ·K 2 +F.sub.(i), a phase estimate loop receiving said phase error signal φ E said bandwidth control signal and said frequency function F and providing the phase function φ.sub.(i+1) =φ E (i) ·K 1 +φ.sub.(i) +F.sub.(i) the values of K 1 and K 2 being selected as a function of coherence function C, and data detection means receiving polar digital signal R, phase estimate signal φ and the phase function output of said phase estimate loop and providing an output D o =R cos φ E therefrom.