UC Davis

Given how much of our current technology relies on the use of wireless sensors, improving communications technology directly benefits consumer products (smartphones, tablets, mobile devices of all kinds), healthcare (mobile monitoring devices, life-saving implants). Therefore, much higher communication speed, lower latency, and cheaper solutions are highly demanding as the technology is moving to the sixth generation (6G). The frequency band from 70 to 100 GHz and 125 to 160 GHz are currently the main focus band for the next generation of wireless communication. Different from wireless communication systems, optical communication involves the transfer of information using light rather than radio frequencies (RF). This method of data transportations has many advantages over standard telecommunications methods, such as improved bandwidth, speed, and power. Optical communication devices have applications in data connectivity (such as cloud storage), transportation networks, CATV systems, submarines, and defense technology. Indeed, as communication technology continues to advance, optical networking devices are becoming a much sought-after commodity. One of the most critical components in wireless communication and optical communication systems is the wideband power amplifiers (PA). Various semiconductor processes have been investigated to support the development of PA for 6G and optical communications systems. By far, Indium Phosphide (InP) and Silicon Germanium (SiGe) process have been proven to be great candidates for the development of the future system thanks to their superior performance in terms of cut-off frequencies. In addition, Indium Phosphide has a significantly higher output power and, therefore, is favorable for high power applications at high frequencies. However, as the operating frequencies emerge into the mm-W region, gain, linearity, and output power degrade rapidly, making the PA highly inefficient and unrealizable. In this dissertation, several original techniques are proposed and implemented to distributed amplifiers and wideband amplifiers. These techniques are applied to demonstrate high-performance power amplifiers up to 160 GHz, potentially enabling the future realization of 6G and the next generation of optical communications. The original techniques are listed as follows: 1. A new bandpass distributed amplifier (DA) using a wideband gain-boosting technique is introduced. A novel feedback network with a series inductor and a shunt capacitor is employed. The traditional theory has suggested that a series inductor only enhances narrowband gain, and a shunt capacitor decreases upper-frequency capacities. However, the combination of these components can obtain a wideband gain enhancement. The proposed amplifier achieves the record gain boosting over the wide bandwidth ever reported. 2. A wideband linearization technique for distributed amplifiers achieves the highest linearization bandwidth. The technique utilizes an auxiliary transistor that generates distortion components, which are the opposite sign of those generated by the main amplifier. The proposed prototype demonstrates the widest linearization bandwidth. 3. A 160 GHz DA with bandwidth improvement using 3-D interdigital capacitors and a 150 GHz using metal-insulator-metal (MIM) capacitors are designed in an InP process. This work demonstrates for the first time that 3-D interdigital capacitors can be used to improve input matching conditions and bandwidth of a distributed amplifier. 4. A linear wideband differential optical driver amplifier in a SiGe process for the next generation of optical communication systems is demonstrated. This is the first time a triple-stacked hetero junction bipolar transistor (HBT) with an emitter degeneration network is employed for optical drivers.