Prediction of error vector magnitude using AM/AM, AM/PM distortion of RF power amplifier for high order modulation OFDM system

This paper presents an analysis of error vector magnitude (EVM) performance of power amplifier using the amplitude/phase distortion coefficients derived from probability density function (PDF) of OFDM input signal. Amplitude coefficient values are calculated from the amplitude/phase distortion coefficients. The amplitude/phase distortion coefficient can be calculated from summation of the measured AM/AM (amplitude distortion) and AM/PM (phase distortion) data considered the probability of an input OFDM signal level. A complete analysis of the EVM model for output OFDM symbol with variable envelop through power amplifier can be derived from amplitude/phase distortion coefficients. To investigate, we use 1024(2¹⁰) IFFT-OFDM signal based on 802.16e mobile system, 9.7dB peak to average power ratio (PAPR) at 0.01% CCDF and 10MHz overall occupation bandwidth, and the fabricated HBT MMIC power amplifier. The error ratio between the predicted EVM and measured EVM is as small as 1%.