A simplified approach for quasi-linear power amplifier distortion evaluation

The paper presents a simplified approach for the evaluation of mild distortion in highly linear power amplifiers (PA) for microwave communications. In particular, it is shown how intermodulation distortion (IMD) can be accurately predicted on the basis of a single-tone power-swept Harmonic Balance analysis instead of using two-tone or multi-tone analyses leading to time-consuming and computationally expensive iterative PA design procedures. Moreover, simple equations provided in the paper show that common design specifications given in terms of maximum acceptable IMD are conveniently converted into constraints on a suitable non linearity index, involving both AM/AM and AM/PM amplifier characteristics. Experimental validation is provided in the paper on the basis of a 50Ω-loaded GaAs 600μm-PHEMT based power amplifier simulated with Agilent ADS.