A 90-W Peak Power GaN Outphasing Amplifier With Optimum Input Signal Conditioning

TLDR

The paper presents a 90‑W peak‑power 2.14‑GHz GaN outphasing amplifier achieving 50.5 % average efficiency for W‑CDMA signals. The amplifier uses two IQ modulators to independently control branch amplifiers, maintaining a constant outphasing angle below a power threshold and enabling input power leveling, which together improve gain, efficiency, and linearity. Experiments confirm that the design achieves high efficiency across a wide bandwidth, operates in class‑B at low output power, meets linearity specifications with simple pre‑distortion, and offers a promising candidate for future multiband base‑station amplifiers.

Abstract

A 90-W peak-power 2.14-GHz improved GaN outphasing amplifier with 50.5% average efficiency for wideband code division multiple access (W-CDMA) signals is presented. Independent control of the branch amplifiers by two in-phase/quadrature modulators enables optimum outphasing and input power leveling, yielding significant improvements in gain, efficiency, and linearity. In deep-power backoff operation, the outphasing angle of the branch amplifiers is kept constant below a certain power level. This results in class-B operation for the very low output power levels, yielding less reactive loading of the output stages, and therefore, improved efficiency in power backoff operation compared to the classical outphasing amplifiers. Based on these principles, the optimum design parameters and input signal conditioning are discussed. The resulting theoretical maximum achievable average efficiency for W-CDMA signals is presented. Experimental results support the foregoing theory and show high efficiency over a large bandwidth, while meeting the linearity specifications using low-cost low-complexity memoryless pre-distortion. These properties make this amplifier concept an interesting candidate for future multiband base-station implementations.