An integrated switchable cascode RF power amplifier in GaN technology

Abstract

In this paper an integrated switchable cascode RF power amplifier (PA) will be presented. Modern communication standards use coding schemes with high peak to average power ratios (PAPR) therefore PA efficiency in back off is key to efficient transmitters. The proposed switchable cascode PA, which is based on a modified cascode structure, is capable of providing such an efficiency peak in back off. The operational principle is explained and a possible circuit implementation in GaN technology at 2.65 GHz is presented. At a maximum power of 2.74 W the circuit has a power added efficiency (PAE) of 65.4 % and at 0.57 W (6.7 dB backoff) a PAE of 60.2 %. In addition the combination with other efficiency enhancement methods such as baseband PWM or direct filter connection are covered.

Equivalent load impedance of pulse width modulation excited band pass filters

“…This problem can be solved by removing the isolator as depicted in Figure 1b and integrating the filter into the matching network [4][5][6][7][8]. The reflections of the filter are now used to achieve efficiency enhancement [4][5][6][7][9][10][11][12][13]. All these methods have in common that they use BB PWM to drive the PA and the following BPF.…”