Search

In this paper, we propose a new compact load network for high-power Doherty amplifiers using an imperfect quarter-wave line. A compact π-network quarter-wave transmission line, which consisted of two shunt capacitors and a series microstrip line, was used to replace a bulky microstrip transmission line. A simple L-C matching network was then deployed after the quarter-wave line. To take the inherent internal parasitic components in the packaged high-power transistors into account, the shunt capacitors of the π-network quarter-wave transmission line were readjusted, which made an imperfect quarter-wave line. For verification, both the conventional and compact Doherty amplifiers were designed and implemented for the 859-MHz band using high-voltage laterally diffused metal-oxide-semiconductor field-effect transistors. The measured linearities and efficiencies of both amplifiers were compared to each other with respect to the reference performance of the class-AB amplifier for two-tone and down-link wideband code-division multiple-access signal excitations. The compact Doherty amplifier with a significantly reduced size for the load network by 75.7% performed even better than the conventional Doherty amplifier. [ABSTRACT FROM AUTHOR]

In this paper, we present a design method for a compact inverted Doherty power amplifier (IDPA), which has high-efficiency and high-power characteristics. An optimum load matching network and an additional offset line, after the matching network of the carrier amplifier, dynamically modulate the load impedance according to the input power drive, while the conventional Doherty power amplifier uses a quarter-wave line to do it. The operational principles and design guide are provided. For experimental verification, a 50-W Doherty amplifier was designed for the π/4 differential quadrature phase-shift keying application at the 860-MHz band. The measured performance of the IDPA was compared with that of the balanced class-AB amplifier with the same output matching network. At an output power of 50 W, the IDPA performs with 3.16 dB better adjacent channel power ratio (-28 versus -24.84 dBc) and 6.15% higher power-added efficiency (59.02 versus 52.87 %) than the class-AB amplifier does. [ABSTRACT FROM AUTHOR]