Sep 26 (Fri) @ 11:00am: "High Efficiency III-V Power Amplifiers Above 100 GHz," Eythan Lam, ECE PhD Defense

Location: Elings Hall, Room 1605
Research Area: Electronics & Photonics
Research Keywords: high frequency, circuit design, power amplifiers, high efficiency

Abstract

Large unused bands above 100 GHz offer opportunities for wide bandwidth applications such as high-resolution radar/sensing, satcom, wireless data centers and IOT. However, scaling up to sub-THz frequencies introduces significant design challenges in power amplifiers (PA). As the frequency is increased, path loss increases which necessitates high output power from arrays. Furthermore, the spacing between array elements also decreases resulting in high power density and significant heating issues, requiring power amplifiers with high efficiencies. Power amplifiers designed in III-V device technologies such as InP offer the highest recorded efficiencies above 100 GHz owing to high fmax/fT and moderate breakdown voltages. For this reason, this work primarily focuses on using InP HBTs for high-efficiency power amplifier design. 

Several high-efficiency D-band (110-170 GHz) and G-band (170-260 GHz) power amplifiers in InP and GaN device technologies are presented. This includes a 135 GHz high-efficiency pseudo-differential class-AB PA in 250nm InP HBT technology with over 30% peak PAE and 19.2 dBm Psat. A 135 GHz pseudo-differential high-power PA in 40-nm GaN HEMT process is also presented with 7.9% PAE and 23.5 dBm Psat. To accommodate high peak-to-average QAM waveforms and high average efficiency, a D-band Doherty PA is demonstrated with a 14.2% peak PAE at 13.7 dBm and 10.6% PAE at 6-dB power backoff. 16, 64 and 256-QAM modulation measurements are then shown with digital predistortion linearization on the Doherty PA. A load modulated tunable varactor PA at 80 GHz is shown, demonstrating feasibility and future opportunities for high average efficiency at high frequency.

Bio

Eythan Lam received B.S. and M.S. degrees in Electrical and Computer Engineering in 2020 and 2024 from the University of California, Santa Barbara. Since 2020, he has been working towards his Ph.D. with research interests in high-efficiency sub-THz power amplifiers and digital predistortion. He worked previously as an intern at the Air Force Research Laboratory at Dayton, Ohio in 2022 and as an intern at Qualcomm Technologies Inc. at San Diego in 2023 and 2024.

Hosted By: Professor James Buckwalter

Submitted By: Eythan Lam <eythanlam@ucsb.edu>