Differential phase shift keyed receiver

Claim 2

A receiver for differential phase shift keyed (DPSK) signals having a baud rate of 1/T symbols per second, wherein products are formed between signals of T second differential delay and wherein polarities of said products decode the phase shifts of the received DPSK signal, including means for phase shifting the received DPSK signal by substantially 90°, characterized by: means for additively combining the 90° phase shifted signal and the received DPSK signal to generate a 45° phase shifted signal; means responsive to the 45° phase shifted signal and to the 90° phase shifted signal for forming a first product therebetween; and means responsive to the 45° phase shifted signal and to the received DPSK signal for forming a second product therebetween.

Claim 3

The receiver according to claim 1 further including means for delaying the 45° phase shifted signal by substantially T seconds; and means for delaying the incoming DPSK signal by Tp seconds prior to additive combination with the 90° phase shifted signal where Tp is the propagation delay associated with the 90° phase shifting means.

Claim 4

The receiver according to claim 1 further including means for periodically sampling amplitude levels of the received DPSK signal; means for storing samples of said DPSK signal; and means for additively combining portions of a plurality of said samples to form the 90° phase shifted signal.

Claim 5

Apparatus for generating reference signals in a receiver for differential phase shift keyed (DPSK) signals wherein products are formed between signals of T second differential delay including, means responsive to the incoming DPSK signal for phase shifting same by 90° to form a 90° reference signal; means for additively combining the incoming DPSK signal and the 90° reference signal to generate a 45° reference signal, and means for correlating the 45° reference signal with said DPSK signal and said 90° reference signal.

Claim 6

Apparatus for generating reference signals in a receiver for differential phase shift keyed (DPSK) signals wherein products are formed between signals of T second differential delay including, means responsive to the incoming DPSK signal for phase shifting same by 90° to form a 90° reference signal; means for additively combining the incoming DPSK signal and the 90° reference signal to generate a 45° reference signal, and means for correlating the 45° reference signal with said DPSK signal and said 90° reference signal.

Claim 7

Apparatus according to claim 4 further including means for additively combining pairs of signals including the incoming DPSK signal, the 90° reference signal and the 45° reference signal to generate additional reference signals whereby incoming DPSK signals having more than four discrete phase states may be demodulated.

Claim 8

A receiver for demodulating a differential phase shift keyed (DPSK) signal having phase changes every T seconds wherein products are formed between signals of T second differential delay and polarities of said products uniquely determine phase shifts of the DPSK signal, including means for phase shifting the DPSK signal by 90°, characterized by: means for additively combining the DPSK signal and the 90° phase shifted signal to form a 45° phase shifted signals; means for delaying said 45° phase shifted signal by T seconds; means responsive to said DPSK signal and to said 45° phase shifted signal for forming a first product therebetween; and means responsive to the 90° phase shifted signal and to the 45° phase shifted signal for forming a second product therebetween.

Claim 9

A receiver for demodulating a differential phase shift keyed (DPSK) signal having phase changes every T seconds wherein products are formed between signals of T second differential delay and polarities of said products uniquely determine phase shifts of the DPSK signal, including means for phase shifting the DPSK signal by 90°, characterized by: means for additively combining the DPSK signal and the 90° phase shifted signal to form a 45° phase shifted signals; means for delaying said 45° phase shifted signal by T seconds; means responsive to said DPSK signal and to said 45° phase shifted signal for forming a first product therebetween; and means responsive to the 90° phase shifted signal and to the 45° phase shifted signal for forming a second product therebetween.

Claim 12

The method according to claim 7 wherein correlation includes the steps of multiplying the signals to be correlated to form products therebetween; and filtering the individual products of said multiplication to extract the polarity of said products.