Quality Monitoring of DxPSK Signals by Using Differential Phasor Diagram

We describe a new method for quantitative evaluation of the quality of multilevel differential phase-shift-keyed (DxPSK) signals by using a differential phasor monitor. This method measures the phase deviation of the symbols in the differential phasor diagram and estimates the bit-error rate (BER) by using a simple relation based on the
Q
-factor defined for multilevel DxPSK signals. We demonstrate that the proposed method can accurately estimate the BER of differential quadrature PSK and 8-ary PSK signals.