We present a method for phase recovery in QAM communication systems based on higher order statistics. Under the assumption that the QAM signals have independent, identically distributed (i.i.d.) in-phase and quadrature components, we derive the relation between the phase error and the fourth-order cumulant of the output. Numerical performance of the approach is demonstrated by computer simulation.

This paper presents the power spectrum of the transmitted signal in a synchronous spread-spectrum communication system in which the users' information symbol sequences are encoded intoM-ary channel symbol sequences. Furthermore, when maximal-length shift register sequences are used as the spreading code sequences of the system, the average power spectrum over all possible sets of the allowable simultaneous users is presented. It is shown that distribution of the spectrum is influenced considerably by the spreading code and the channel symbol sequences.

Using the direct method of analysis, the power spectrum of the output phase rate of a FDM-FM signal passed through a transmission system with AM-PM converter is expressed by four kinds of components for both cases with and without preemphasis. It is illustrated that signal-to-interference ratios are in good agreement with Monte Carlo computations. Further, based on the evaluations of the spectral components and mean-square error, in baseband, the effects of these components are elucidated.