Radio receivers for cellular networks: Possible architectures using a ΣΔ-converter

We first explain the constraints set on a receiver for digital cellular systems before showing how they are handled with the standard architectures (direct conversion and superheterodyne). We introduce then a new approach based on the direct sampling of the intermediate frequency in a superheterodyne receiver using a passband analog- to- digital ΣΔ -converter. We give design rules to minimize the complexity of the system and study within that scope the interest of under sampled ΣΔ -converters addressing more especially the stability problems. Undersampling allows to reduce the processing load in the digital part of the converter, compared to a standard ΣΔ conversion. The last chapter is dedicated to a presentation of cellular networks in order to justify the constraints set on receivers designed for this environment.