AlGaN/GaN High electron Mobility Transistor (HEMT) based radio frequency power amplifiers for future wireless communication transmitters: Exciting prospects and challenges

The power amplifiers (PAs) are indispensable for maintaining that both space and terrestrial transmitters fulfill the rigorous requirements for power consumption and, consequently, efficiency. Since solid-state PAs based on GaN HEMTs may offer the efficiency and power density performance to make them a feasible choice for space-borne active antennas, their availability is what propels integration for the satellite transmitters. Gain, output power (P_out), bandwidth (BW), drain efficiency (DE), chip area, peak-to-average-power ratio (PAPR) and power added efficiency (PAE) are the key metrics usually used for measuring the performance of PAs. This article deals with the exciting prospects and challenges in the design and manufacturing of GaN-HEMT based RF-PAs. Doherty PAs are most popular among various PA architectures and they have recorded a maximum gain of over 30 dB, PAPR of over 11.5, PAE of over 81 % and an operating frequency of over 29 GHz. Other GaN HEMT based PAs have been reported a maximum operating frequency of over 192 GHz (using 100 nm GaN HEMT), gain of over 35 dB, and a P_out of over 282 W. This article also highlights the various techniques for enhancing the broadband operation of GaN HEMT based PAs.