A novel phase measurement technique for IM3 components in RF power amplifiers

This paper presents a novel measurement technique to measure the phases of intermodulation (IM) components of RF power amplifiers (PAs) with low-cost. This method can measure the phase distortions of the third-order IM components, as well as the fundamental signals generated in the PAs themselves by directly comparing the respective IM components before and after the PAs. A 45-W RF PA with an LDMOSFET in the wide-band code-division multiple-access band is implemented, and the relative changes of the IM phases of the PA are presented under various tone spacings, output power levels, and gate bias voltages. This system is very convenient for evaluating the memory effects of the PAs, and is helpful for the design of predistortion PAs and for the model extraction of PAs.