A 28-GHz inverse class-F power amplifier with coupled-inductor based harmonic impedance modulator

This paper presents a 28 GHz class-F¹ power amplifier in 0.13-μm SiGe BiCMOS technology. The PA adopts a coupled-inductor based harmonic impedance modulator in order to terminate 2^nd and 3^rd harmonic load impedances appropriately for class-F¹ operation. The coupled coils essentially provide frequency-dependent inductance that is optimal to resonate out 2^nd and 3^rd harmonic reactive impedance. The PA achieve 40–42% PAE over 27.5 GHz to 29 GHz, peak 42% PAE at 28 GHz with 50 mW OP-1db power, one of the highest PAEs ever reported in silicon-based PAs. At 6-dB backoff output power, the PAE is as high as 20% Psat is 16.6 dBm. The PA occupies 0.55×0.96 mm².