Distributed Class-J Power Amplifiers

Abstract

This paper presents the design and implementation of a distributed class-J power amplifier (DJPA) in a 0.25- $\mu \text{m}$ AlGaAs–InGaAs pHEMT technology. Class-J mode of operation is introduced in design of distributed power amplifiers (DPAs) to achieve high power added efficiencies (PAEs) over wide frequency ranges. Extensive load–pull (LP) and source–pull (SP) simulations are performed to show that class-J PAs are less sensitive to proper termination of higher order harmonics, and high PAE and output power can be obtained even if the second, third, fourth, and fifth harmonics comprise a real impedance. This is essential in DPAs as the higher order harmonics of the frequencies at lower side of the band may fall in the desired bandwidth. Based on LP and SP observations, a proof-of-concept 1.5–10-GHz monolithic microwave integrated circuit DJPA is designed and fabricated. Chip dimensions are $2.15\times 2.15$ mm2, and 29–30.7-dBm output power with 33–44% PAE is achieved over the frequency range. The large-signal power gain is greater than 10 dB while the PA maintains an average small-signal gain of 13 dB over the bandwidth.