Contents 1 INTRODUCTION
A single-chip implementation of a transceiver would be a cost-effective solution for many wireless applications. However, it sets additional requirements on the architecture of the RF part. For example, to avoid the use of components that are difficult to integrate (e.g. RF bandpass filters) direct downconversion instead of superheterodyne is used. Another important requirement is that the transceiver analog and RF parts are not too much disturbed by the switching activity of its digital part: the digital switching noise (generated by the digital part) couples to the common substrate, propagates through it to the analog and RF circuits and can severely degrade their performance. With today's ever-decreasing transistor sizes and supply voltages, latch-up becomes very hard to occur and highly doped (low-ohmic) substrates with an epitaxial layer are replaced by cheaper lightly doped (high-ohmic) substrates. For these lightly doped substrates less has been reported on substrate noise coupling [2], [3] than for the highly doped substrates [1]. Moreover, the few experimental studies published on the performance degradation of analog /RF circuits due to substrate noise concentrate mainly on highly doped substrates [4]. In order to help RF designers protect analog circuits against substrate noise (by using guard rings, physical separation, etc.), a good understanding of both noise propagation and impact on RF circuits in lightly doped substrates is mandatory. In this document, both propagation and impact are studied using measurements. The performance degradation due to substrate noise is studied as the cascade of an attenuation through the substrate from the source of noise to different sensitive parts of the RF circuit and the propagation through this RF circuit to its output. This approach gives insight in the mechanisms of substrate noise impact on RF circuits.
