Device for phase synchronizing a reproduced reference carrier signal with windows specified for preselected ones of amplitude and phase modulated signal points

For use in a receiver for an incoming amplitude and phase modulated signal selectively representative of true signal points (X.sub.i, Y.sub.i), N in number, arranged on an X-Y complex amplitude plane, a phase synchronizing device for phase synchronizing a reproduced reference carrier signal with an incoming reference carrier signal defining said X-Y plane and contained implicity in said incoming modulated signal, comprising:

• a demodulator responsive to said incoming modulated signal and said reproduced carrier signal for producing complex signals selectively representative of coarse signal points (x.sub.i ', Y.sub.i ') distributed on said X-Y plane around said true points,
• a window specifier responsive to said complex signals for producing window signals defining predetermined areas on said X-Y plane which include predetermined ones, n in number, of said true points, n being not greater than N,
• means repsonsive to said complex signals and said window signals for producing difference signals representative of differences (x.sub.j, y.sub.j) in X and Y components between said true points and the coarse points included in said areas,
• means for calculating a linear sum of the differences, p in number, in the X components and the differences, q in number, in the Y components to produce a sum signal representative of said sum, p and q being not greater than n and not simultaneously equal to zero, and
• means responsive to said sum signal for phase controlling said reproduced carrier signal.