Measurement and simulation of memory effects in predistortion linearizers

Detrimental effects of memories in linearizers are described, and two efficient techniques are presented to measure them. These techniques allow a real-time adjustment and correction of the linearizer and/or amplifier circuits and an overall improvement of the intermodulation performance over a wide envelope frequency band. This is especially important for broadband applications, where high efficiency and linearity are required, and where memory effects, if not detected and properly corrected, may significantly degrade the system´s performance. Experimental results for a 20-W linearized L-band power amplifier are presented to illustrate the effects of memory. The two techniques-a dynamic AM/AM and AM/PM measurement system and a pulse power measurement system-are described. A simulation approach that can be used to predict the influence of memory effects in practical systems is illustrated for nonlinear amplifiers. Adaptive linearization techniques are discussed