Digital band-pass detector

Claim 1

A digital band-pass filter detector comprising first, second, third and fourth delay elements in the form of shift registers, having preselected delays of Tau , Tau , 2 Tau , and 4 Tau , respectively, clock means providing a clock pulse of predetermined frequency to said delay elements, the first of said delay elements receiving an input signal in the form of a square wave, said first delay element providing a first output signal with a delay of Tau , the second of said delay elements receiving said first output signal and providing a second output signal with a delay of 2 Tau , the third of said delay elements receiving said second output signal and providing a third output signal with a delay of 4 Tau , the fourth of said delay elements receiving said third output signal and providing a fourth output signal with a delay of 8 Tau , means to invert said first output signal 180*,a first full wave digital phase detector receiving simultaneously said inverted first output signal and said input signal to provide a first phase detected signal, a second full wave detector receiving simultaneously said second output signal and said input signal to provide a second phase detected signal, a third full wave digital detector receiving simultaneously said third output signal and said input signal to provide a third phase detected signal, a fourth full wave digital phase detector receiving simultaneously said fourth output signal and said input signal to provide a fourth phase detected signal, and AND gate means receiving simultaneously said first, second, third, and fourth phase detected signals and in response thereto providing a filtered DC output signal.