Continuous harmonically tuned Class-B power amplifier: A closed form equation design approach

This paper presents a set of closed form equations for the calculation of the impedances for the continuous harmonically tuned (HT) Class-B power amplifier (PA). These equations have been derived by assuming a “quartic” drain current rather than the usually assumed half-wave rectified sinusoidal wave current. The resulting impedances were verified in simulations using a proven, large-signal GaN transistor model at three frequencies (900MHz, 2.1GHz and 3.5GHz). Moreover, a PA was built and measured at 2.1GHz, based on a 10W GaN HEMT transistor, achieving a power added efficiency (PAE) of 72.8% at maximum output power confirming the proposed design approach.

I. Introduction

Contemporary communication systems use extended channel bandwidths to deliver the required data rates, which current implemented amplifiers are struggling to achieve, while trying to reduce operation expenses (OPEX) of the operators. For the aforementioned reasons, there is increasing interest in broadband power amplifiers (PA) with improved efficiency and linearity without the reduction of delivered power.