A Reflective Analog Predistorter with Independently Tunable Phase

This paper proposes an independently tunable analog predistorter based on a 3 dB coupler. It can be cascaded with a predistorter with independently tunable gain to form a linearizer with both gain and phase independently tunable. The impact of the loads connected to the coupled and through ports of the 3 dB coupler on the amplitude-phase characteristics is analyzed. To validate the method, a predistorter was designed and fabricated at 3.4 GHz. The measurement results indicate that the tuning range of AM-PM is over 21°, and that of AM-AM is less than 0.2 dB. A power amplifier with a 20 MHz 64-QAM signal stimulated is linearized by the linearizer, and the adjacent channel power ratio (ACPR) can be improved by 9.4 dB.