RF CMOS NOISE CHARACTERIZATION AND MODELING

Abstract

This paper presents a through description of radio frequency (RF) noise characterization and modeling of CMOS transistors. It begins with the definition of the four noise parameter of a two-port network - minimum noise figure (NFmin), equivalent noise resistance (Rn), optimized source impedance (Ropt) and optimized source reactance (Xopt). These four parameters are used in device characterization and it is shown how they can be calculated by using the noise two-port network theory and a circuit simulator. Then two de-embedding procedures are discussed in detail for noise and scattering parameter de-embedding to get rid of the parasitic effects from the probe pads and interconnections in the device-under-test (DUT). Ideally there is no frequency and geometry limitation for the method based on a cascade configuration. Methods to directly extract the channel noise, induced gate noise and their correlation from the RF and noise measurements are developed and the extracted noise sources as a function of frequency and bias condition for different channel lengths a presented. Some design consideration for the design of low noise circuits - how to select the device size, choice of DC bias conditions and design device layout, are presented. Finally, some published noise models for the channel noise, induced gate noise and their correlation are discussed.