Design of wideband silicon-germanium RF front end circuits for broadband communications systems
Rao, Sunil Gururaj
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This thesis discusses the design of wideband front-end circuits for broadband communications systems, designed in silicon-germanium technology. The bandwidths of these circuits cover from 2 GHz to 18 GHz. In Chapter 1, an introduction to wideband communications systems is presented. In addition, a brief summary of phased array radars and the need for wideband radars are discussed. Also, an overview of Silicon-Germanium technology and its advantages in the context of wideband circuit design are discussed. In Chapter 2, the design challenges associated with wideband RF front-end circuits are presented. In particular, the design space of wideband power amplifiers and low-noise amplifiers is discussed. Both the active and passive circuit design difficulties for each circuit are evaluated. In addition, traditional approaches to amplifier design and their drawbacks for wideband circuits are explained. In Chapter 3, the design of a wideband 1-20 GHz Silicon-Germanium power amplifier is discussed. In this design, a distributed amplifier topology is utilized with transistor stacking to simultaneously achieve high output power and wideband impedance matching. This amplifier is designed in a highly scaled 90 nm SiGe BiCMOS process. Measurement results and a comparison to state-of-the-art wideband power amplifiers are shown. This work, ”A 1-20 GHz Distributed, Stacked SiGe Power Amplifier” was published in the 2018 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium . In Chapter 4, the design of a wideband 1-18 GHz Silicon-Germanium low noise ampli- fier is presented. A resistive feedback topology is used to achieve wideband operation with moderate gain and low noise figure. In addition, a cryogenic characterization of this amplifier is conducted with measurements of S-parameters, 1 dB compression point, and noise over temperature. A comparison to state-of-the-art cryogenic amplifiers is shown. Furthermore, the demonstration and explanation of an on-wafer cryogenic noise measurement scheme are presented. This work, ”A Low Power, Wideband SiGe Low Noise Amplifier for Cryogenic Temperature Operation” will be submitted to the 2019 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS). In Chapter 5, a summary of the achieved results is shown. In addition, future research directions are discussed.