A Highly Efficient X-Band Inverse Class-F SiGe HBT Cascode Power Amplifier With Harmonic-Tuned Wilkinson Power Combiner

A highly efficient sub-Watt X-band inverse class-F SiGe heterojunction bipolar transistor (HBT) cascode power amplifier (PA) is presented. With a multi-harmonic resonance filter and a low loss lumped-element Wilkinson power combiner as an output matching network, the inverse class-F operation is realized successfully and high output power and power added efficiency (PAE) are obtained simultaneously. A cascode configuration with a low base impedance termination and reduced voltage-current waveform overlap extends VCE swing of the upper SiGe HBT in the cascode beyond BVCBO, leading to improvement in output power and PAE. As proof of concept, the proposed PA was implemented in a 0.13-μm SiGe BiCMOS technology platform. Measured results shows 53.4% peak PAE with 26.1 dBm output power at 10 GHz, when operated on a 3.0-V supply. No performance degradation is observed after 24-h continuous mode operation. To the author's best knowledge, this brief has the highest PAE among any Si-based X-band PAs with comparable output power, which demonstrates that the proposed harmonic-tuned Wilkinson power combiner approach is an appropriate solution for efficient PA design at X-band.