Modelling of Substrate Noise and Mitigation Schemes for UWB Systems

The last chapter of this first part of the book, chapter seven, is devoted to Modeling of Substrate Noise and Mitigation Schemes for Ultrawideband (UWB) systems, and is written by Ming Shen, Jan H. Mikkelsen, and Torben Larsen from Aalborg University, Denmark. In highly integrated mixed-mode designs, digital switching noise is an ever-present problem that needs to be taken into consideration. This is of particular importance when low cost implementation technologies, e.g. lightly doped substrates, are aimed for. For traditional narrow-band designs much of the issue can be mitigated using tuned elements in the signal paths. However, for UWB designs this is not a viable option and other means are therefore required. Moreover, owing to the ultra-wideband nature and low power spectral density of the signal, UWB mixed-signal integrated circuits are more sensitive to substrate noise compared with narrow-band circuits. This chapter presents a study on the modeling and mitigation of substrate noise in mixed-signal integrated circuits (ICs), focusing on UWB system/circuit designs. Experimental impact evaluation of substrate noise on UWB circuits is presented. It shows how a wide-band circuit can be affected by substrate noise. This chapter also presents a new analytical model for the estimation of the spectral content of the switching noise. In addition a novel active noise mitigation scheme based on spectral information is presented.