1.8 GHz power amplifier for wireless front-end

Abstract

This project presents a differential power amplifier (PA) with low second-order harmonic distortion for wireless communications systems. The PA is critical to any wireless transmitter. It pushes the signal power level to compensate the path loss in the wireless commendations so that the wireless product can work for long distance. When the PA works as large signal amplification, it becomes nonlinear. Second and higher order harmonics will be generated to interfere other wireless product. In fact, second harmonic power should be highly suppressed by additional integrating low pass or band pass filter at the PA output. In this project, a wideband differential PA was designed at the centre frequency of 1.8GHz, while a simple balanced PA with in-phase power divider/combiner was also designed for reference. The maximum PA output power is 25.65dBm. The differential PA achieves not only 39.45dBc second harmonic suppression at 1.8GHz, but also 31.77dBc and 33.89dBc suppressions at 0.9GHz and 2.4GHz, respectively. Besides, a 1.8 GHz differential active integrated antenna was designed. The differential antenna replaces the differential power combiner to save circuit area. It also shows 37.4dBc second harmonic suppression at 1.8GHz.