Design of a Tri-Band Doherty Amplifier Based on Generalized Impedance Inverter

Abstract

This paper introduces a methodology for implementing multi-band Doherty power amplifiers. Traditionally, a 90∘ impedance inverter line is required in Doherty architecture. In this contribution, a generalized impedance inverter line is utilized to construct multi-band Doherty power amplifiers. A tri-band Doherty power amplifier operating at 1.15, 1.85 and 2.55[Formula: see text]GHz is designed to validate the proposed method. Measurement results show the fabricated Doherty power amplifier achieves 6[Formula: see text]dB output back-off drain efficiencies of 62.3%, 49.3% and 50.5% at 1.15, 1.85 and 2.55[Formula: see text]GHz, respectively. The peaking output power of the fabricated tri-band Doherty power amplifier is 43.2, 43.7 and 43.8[Formula: see text]dBm with drain efficiencies of 64.5%, 62.2% and 64.5% at three working frequency points, respectively. Furthermore, when the designed Doherty power amplifier is driven by a 20[Formula: see text]MHz wideband LTE signal with peak-to-average-power ratio of 6.4[Formula: see text]dB, adjacent channel power ratios of [Formula: see text]29.4 and [Formula: see text]57.1[Formula: see text]dBc are achieved before and after digital pre-distortion at 1.85[Formula: see text]GHz.