Nonlinear Effects of Power Amplifiers on Adaptive Antenna Systems

A systematic method is first proposed for numerically analyzing the nonlinear effects of a power amplifier on adaptive arrays. By using the proposed method, the bit error rate (BER) degradation caused by the nonlinear distortion of amplifiers on a nine-element adaptive antenna system (AAS) was numerically analyzed using a least mean square (LMS) adaptive algorithm. A closed form was first derived to analyze the radiation pattern degradation of the null shifting caused by the amplifier's nonlinear distortion. The obtained data were then compared with the measured results of a two-element antenna array with two amplifiers. The concordance of the theoretical and measured data verified the proposed method.