EFFECTS OF NON- LINEAR AMPLIFICATION ON N-GMSK AND N-FQPSK SIGNAL STATISTICS

Abstract

Digital modulation schemes that are power and bandwidth efficient are highly desirable. After non-linear amplification has been done, signal modulation schemes having constant or quasi-constant envelopes are not as susceptible to spectral regrowth as those with non-constant envelopes. Since such distortion generates interference in the adjacent channels, the power operation of the amplifier in non-constant envelope modulations is typically backed off, resulting in systems with reduced power efficiency. On the other hand, constant envelope modulation may have different bandwidth spectra. This paper examines the statistical characteristics of N-GMSK and N-FQPSK [1] signals to assess the bandwidth efficiency in the presence of amplifier nonlinearities.