RADIO RECEIVERS FOR CELLULAR NETWORKS POSSIBLE ARCHITECTURES USING A SIGMA-DELTA-CONVERTER

We first explain the constraints set on a receiver for digital cellula r; systems before showing how they are handled with the standard archi tectures (direct conversion and superheterodyne). We introduce then a new approach based or the direct sampling of the intermediate frequenc y in a super-heterodyne receiver rising a passband analog-to-digital S igma Delta-converter. We give design roles to minimize the complexity of the system and study within that scope the interest of under sample d Sigma Delta-converters addressing more especially the stability prob lems. Under-sampling allows to reduce the processing load in the digit al part of the converter, compared to a standard Sigma Delta conversio n. The last chapter is dedicated to a presentation of cellular network s in order to justify, the constraints set on receivers designed for t his environment.