Phase-diversity hybrid optimization in case of a two-detector receiver

The performance of two-detector phase-diversity circuits is investigated in the case of restricted local oscillator power. A 120 degrees hybrid with 33.3% throughput is found to be optimum for CPFSK, while a 90 degrees hybrid with 29.3% throughput is optimum for ASK and DPSK. The sensitivities of these hybrids are 1.87 and 1.37 dB, respectively-better than that of the conventional 90 degrees /25% hybrid. The novel 90 degrees /29.3% hybrid can be implemented as a partially symmetric 3*3 coupler or as a polarization-type phase-diversity hybrid.<
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