Serial demodulation of an OQPSK direct sequence spread signal

Abstract

A general equation is derived for modulation waveforms which can be serially demodulated. This equation is used to define the modulation structure for SOQPSK (serial offset quadrature phase shift keying). Coherent serial demodulation is shown to perform with the same BER (bit error rate) peeeance as a parallel demodulator for the condition of optimum correlation detection. Serial noncoherent detection is shown to provide intersymbol interference which increases the false correlation level if the spreading codes are not chosen properly. A computer simulation was developed which allowed the performance of coherent and noncoherent SOQPSK detection to be studied. The simulation results verified the analytical calculations.<>