Quadrature Clock Modulation Versus Binary and Quadrature Phase Shift Keying in the Presence of Intersymbol Interference.

摘要

Quadrature Clock Modulation (QCM) is a binary phase shift keying (BPSK) technique in which alternate bits are transmitted orthogonally. Compared to normal BPSK modulation, QCM improves the performance of a communication system which is limited by intersymbol interference (ISI). Compared to quadrature phase shift keying (QPSK) for the same information rates, QCM is slightly inferior in data detection performance. The average carrier tracking capability of a QCM scheme is equal to that of BPSK for the same closed-loop bandwidth and time bandwidth product (BT) of the channel filter at a specified signal energy to noise ratio (Eb/No). The data detection performance for QCM, BPSK, and QPSK is analyzed by comparing the one-shot probability of error conditioned on a phase error as a function of Eb/No and BT for a specified channel filter. Carrier tracking performance for QCM and BPSK is analyzed by obtaining an average phase error variance for the linear model of a Costas loop.