The effect of harmonic load terminations on RF power amplifier linearity for sinusoidal and /spl pi//4 DQPSK stimuli

The effect of harmonic load terminations on the linearity of a GaAs MESFET power amplifier is examined for both sinusoidal and /spl pi//4 DQPSK stimuli. A large signal model is utilized with harmonic balance and envelope simulation methods to predict distortion performance of a GaAs MESFET based RF power amplifier targeting domestic TDMA cellular radio handset applications. The simulation techniques and large signal model are first validated by comparing load pull distortion measurements arising from both sinusoidal and digitally modulated RF stimuli to simulation. Excellent agreement between measurement and simulation is observed for a wide range of load line conductances. The effect of harmonic terminations on amplifier linearity is then investigated using simulation methods. The results suggest significant linearity improvements are possible with proper harmonic terminations.