Bandwidth Enhanced Doherty Power Amplifier Based on Coupled Phase Compensation Network With Specific Optimal Impedance

Abstract

This paper presents a new technique to dramatically enhance the bandwidth of a post-matching Doherty power amplifier (PM-DPA). This technique relies on using a coupled-line phase compensation network (PCN). Through a theoretical analysis, we first point out this coupled-line PCN can offer wideband impedance matching due to its capacity in reducing the external Q-factor of the peaking branch. Then, our analysis guides the derivation of closed-form formulas that help to determine the physical parameters of the coupled PCN. Finally, when augmented with suitable selected peaking amplifier impedances, the proposed technique allows improved peak efficiency and output power over extended bandwidth. For experimental verification, A DPA based on commercially available GaN high-electron-mobility transistor (HEMT) devices (Cree CGH 40010F) has been designed and fabricated. Measured results of the proposed DPA shows 6 dB back-off operation between 1.3 - 2.3 GHz (55% fractional bandwidth) with efficiency in excess of 41%.