Communication system performance - detailed modeling of a power amplifier with two modulated input signals

The performance of multicarrier frequency division multiple access (FDMA) wireless communication systems is impacted by amplifier nonlinearities. It is vital to precisely model limiters and high power amplifiers (HPAs) to determine the spectrum distortion and other types of degradation associated with multicarrier communication systems. Contemporary simulation tools can be employed to precisely ascertain intermodulation (IM) distortion and its effect and impact on both in-band and out-of-band IM performance in a computationally timely manner. This paper illustrates analysis and simulation results in a parameterized form when the amplifier input consists of two 8-PSK modulated signals with raised cosine filter shaping. One of the significant parameters in these analyses and simulated results is the HPA operational back-off (OBO) power level, which is studied over a range of about 6 dB. The simulation illustrates the intermodulation distortion both within the signal band and outside the signal band. A novel approach is used to represent an HPA in terms of a power series expansion, which converges very rapidly and gives significant insight and provides a useful tool in predicting the spectral content of the HPA output. The results contained in this submission were generated in whole, or in part, through work supporting the MILSATCOM joint program office (MJPO). The authors are very appreciative of the support provided by the SMC/MC program office of the Space and Missile Center in this effort