Theories, design methodology, and implementations of subthreshold CMOS RF analog designs for ultra low power applications
Abstract
CMOS RFICs are typically designed with MOS transistors operating in strong inversion regime (or superthreshold). As the CMOS process technology scales down and improves up to deep-submicron, subthreshold biased MOS transistors becomes good candidates for low power high frequency analog and RF circuit applications. In this thesis, the possibilities of using CMOS transistors operating in subthreshold regime to design ultra low power RF integrated circuits are sought both theoretically and experimentally. Theory, design methodology, implementations, and experimental verification of subthreshold CMOS RF design for ultra low power are presented. Analytical modeling of MOS transistor characteristics biased in subthreshold regime including gain to DC power ratio, operating frequency limitation, noise characteristics and linearity characteristics are derived. Following the analytical models, a subthreshold RF design methodology is established. The proposed analytical models and design methodology of subthreshold RF designs are validated through the implementation of three subthreshold RF building blocks namely low noise amplifier (LNA), down converting mixer, and voltage controlled oscillator (VCO). At 3GHz, the implemented subthreshold LNA has a measured gain of 9.1dB and a noise figure of 4.7dB at a power dissipation of only 400uW. The implemented subthreshold frequency down converting mixer has a measured conversion gain of 15.7dB and a noise figure of 18.3dB at 500uW power consumption. The measured phase noise of the implemented subthreshold LC VCO is - 106dBc/Hz at 400kHz offset from 2.63GHz oscillation frequency at only 430uW power consumption. The overall performance of the implemented subthreshold RF building blocks measured by various figures of merit, are shown to be superior to the reported state of the art low power CMOS RF circuits implemented using standard CMOS superthreshold design.
Degree
Ph.D.
Advisors
Mohammadi, Purdue University.
Subject Area
Electrical engineering
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