UC Davis

Abstract

The rapid advancement of next-generation wireless communication systems, autonomous driving technologies, and the Internet of Things (IoT) has created an increasing demand for high data rates, lower latency, and improved network capacity. To meet these requirements, the sixth-generation (6G) wireless communication networks are moving towards frequencies above 100 GHz, where a broader spectrum can be utilized, facilitating the effective integration and functioning of sophisticated communication systems and IoT applications. Developing transceivers for sub-terahertz (sub-THz) frequencies requires the optimization of radio frequency (RF) front-end components, which play a crucial role in determining the overall system performance. Power amplifiers, in particular, are essential in the transmitter because they are responsible for amplifying the signal prior to transmission. Moreover, achieving high output power across an extensive system bandwidth is necessary for efficient signal transmission. Additionally, the power amplifier is among the most power-consuming components within a transceiver system, making the minimization of power consumption highly desirable.In this dissertation, the designs and implementations of wideband power amplifiers for sub THz frequencies are explored. The wideband power amplifiers utilizing an Indium Phosphide (InP) heterojunction bipolar transistor (HBT) process are presented, which employ a common base double-stack (CB 2-stack) with a split-top topology to achieve high gain and output power across a wide bandwidth. One power amplifier demonstrates an average gain of 16 dB and a maximum 3-dB bandwidth of 73 GHz, ranging from 130 to 203 GHz, with the measured saturated output power (Psat) higher than 10 dBm up to 170 GHz. In order to attain increased gain and output power, the second design incorporates both a cascade topology and power combiner into the pre-existing common base PA. The simulation achieved a gain of 23 dB and Psat exceeding 12.4 dBm at 170 GHz. The distributed amplifier (DA) architecture is explored in pursuit of broader bandwidth. Wideband DAs, utilizing an InP HBT process with a triple-stacked topology, are designed to achieve high gain and output power. Emitter resistive-capacitive (RC) degeneration, capacitive coupling, and mixed-gain cell topologies are incorporated in DAs to attain bandwidths of 182 GHz, 210 GHz, and beyond 220 GHz, respectively. The DAs provide a measured gain of more than 11 dB across the design bandwidth, achieving a maximum Psat of 14.8 dBm while maintaining over 12.3 dBm Psat up to 175 GHz. To further enhance the output power of the DA, a wideband, high output power quadruple-stacked HBT DA is designed and developed. This quadruple-stacked configuration elevates gain and output power while preserving extensive bandwidth. Measurement results exhibit a gain of 16 dB and a bandwidth spanning from 7 to 115 GHz. The quadruple-stacked DA achieves a maximum Psat of 24 dBm.