A 44-64 GHz Broadband 90o Hybrid Doherty PA with Quasi Non-Foster Tuner in 0.13μm SiGe

This letter presents a simultaneous broadband and back-off efficient mm-wave linear Doherty PA utilizing quadrature hybrid and a Doherty bandwidth enhancement technique exploiting quasi non-Foster impedance synthesis at the quadrature isolation port. We show analytically the design methodology of the non-Foster synthesis with ON-chip impedance tuner that allows broadband back-off efficiency, without suffering from nonlinearity due to the low-leakage power of the isolated port. Across 44–64 GHz, the proposed SiGe PA achieves collector efficiency of 26%–34.7% at peak power and 14%–23.2% at 6 dB back-off with 18.5–21.5 dBm Psat and peak gain of 18.5 dB. It supports 6 Gbps 64 QAM signal with −26.5 dB/−28.3 dBc EVM/ACLR at average Pout/PAE of 14.6 dBm/14.6% at 54 GHz. To the best of the authors’ knowledge, this work achieves highest bandwidth among silicon-based mm-wave power amplifiers (PAs) where higher than class-B back-off efficiency is achieved.