| This dissertation explores the design of Silicon-Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) power amplifiers for radar applications at X-Band (8-12 GHz) and above. As successive generations of SiGe become faster and faster, they consequently experience decreasing breakdown voltages. This lack of breakdown voltage presents a fundamental challenge for power amplifiers to achieve necessary output power and efficiency parameters for the systems in which they operate. Novel techniques for increasing breakdown voltage as well as techniques for thermally optimizing power amplifier cells are investigated.;For X-Band power amplifiers, this dissertation covers: (1) A mixed breakdown cascode architecture for increased breakdown voltage in SiGe (Chapter II, also published in [1]). (2) A high-gain two-stage power amplifier operating from 8.5 to 10.5 GHz with a nominal output power of 20 dBm and a Power-Added-Efficiency (PAE) of 25% (Chapter III, also published in [2], [3], and [4]). (3) A high power SiGe amplifier with a near one Watt output power (Chapter IV, also published in [5]).;Additionally, techniques for thermally modeling and optimizing power amplifier structures in commercially available design kits are presented. For thermal optimizing and modeling the dissertation covers: (1) Analysis of thermal coupling between adjacent devices through the use of infrared imagery (Chapter V, also published in [6]). (2) Modeling and optimization techniques in commercially available software, exhibited through the thermal balance of a multi-transistor array (Chapter VI, also accepted for publication in IEEE Transactions on Electron Devices). |
