Enhanced delay alignment method for behavioral modeling of power amplifiers exhibiting memory effects

In this paper, the impact of memory effects on the delay estimation in power amplifiers behavioral modeling applications is investigated. It is shown that conventional cross-correlation based delay estimation is affected by the presence of memory effects. This results in a delay estimation error that impacts the performance of the derived behavioral model. Thus, rather than aligning the measured input and output waveforms using the time delay estimated using the actual measured data, a time delay derived under memoryless condition is used. The proposed method is experimentally validated using a 3G Doherty power amplifier driven by 3-carrier and 4-carrier WCDMA signals. For each signal, several memory polynomial behavioral models were derived. It is demonstrated that the use of the proposed delay alignment approach results in enhanced modeling performance. For the 4-carrier WCDMA signal, the NMSE calculated for the behavioral models derived using the proposed delay alignment technique is approximately 3.5 dB better than that calculated for the behavioral models derived using the conventional time delay alignment method.