Title:  Design of Broadband Linear and Efficient Mm-Wave Power Amplifiers in Silicon for 5G Applications

Committee:

Dr. Hua Wang, ECE, Chair , Advisor

Dr. Gee-Kung Chang, ECE

Dr. John Cressler, ECE

Dr. Justin Romberg, ECE

Dr. Peter Asbeck, UCSD

Abstract: To address the exponential growth in data rate and capacity demand, wireless communication is evolving towards 5G and beyond. This poses increasingly stringent performance requirements on RF frontends including PA, LNA, switch, phase shifter, and VGA etc. PAs interface the transmitter systems and antennas and are emerging as the key building block in RF frontends. This is because the PA characteristics such as the output power, energy efficiency, operating bandwidth, and linearity are critical for overall system performance including link budget, power consumption/thermal management/battery life, data rate/frequency agility, and data error rate/spectrum compliance. Furthermore, most of the PA performance metrics trade with each other, making the design a multidimensional problem in practice. Moreover, compared to other building blocks, PAs often encounter unique design challenges and tradeoffs due to their large-signal and high-power operations. Although compound semiconductors traditionally dominate the mm-Wave designs, silicon is now emerging as a promising platform for mm-Wave applications. Its key advantages include low cost, high integration, matured modelling and so on.  Moreover, the unparalleled computation capability in silicon naturally allow the design and implementation of sophisticated circuits and systems that can potentially augment and optimize silicon PA performance, such as the linearity-efficiency trade-off. However, silicon devices often present inferior device-level capabilities than compound devices, such as low breakdown voltage and low efficiency, which hampers silicon mm-Wave 5G PA performance in practice. Thus, innovations at the architecture-/circuit-levels should be leveraged to overcome these device-level limitations of silicon. In this dissertation, I present the design approaches towards broadband efficient high-power mm-Wave 5G PAs, including: a fully integrated high-power broadband linear Doherty PA with multi-primary distributed-active-transformer (DAT) power-combining; a mixed-signal Doherty PA for simultaneous linearity and efficiency enhancement; an instantaneously broadband PA with distributed-balun output network; an AI-assisted mm-Wave Doherty PA with rapid mixed-mode in-field performance optimization.