Reconfiguration of Cascade LA / Modulators for Multistandard GSM/Bluetooth/UIMTS/WLAN Transceivers

Abstract- This paper presents design considerations for cas- ment fast digital circuits than precise analog functions [5]. cade Sigma-Delta Modulators (XAMs) included in multistan- Several multistandard LAM Integrated Circuits (ICs) have dard wireless transceivers. Four different standards are been reported up to now [6]-[10]. Most of them are based on covered: GSM, Bluetooth, UMTS and WLAN. A top-down reconfiguring architecture-level parameters (modulator order, design methodology is proposed to find out the optimum mod- oversampling ratio and/or number of bits of the internal quan-ulator architecture in terms of circuit complexity and reconfig- tizers), whereas less emphasis is normally put at circuit-level uration parameters. The selected 2-1L-2 expandible YAM is parameters. high-level sized and several reconfiguration strategies are This paper presents design considerations applicable to adopted at both architecture- and circuit-level in order to This padepr AMs integnedonsideratistandableto adapt the modulator performance to the different standards expandible cascaderAMs intended for multistandard receiv-ers coeigfustnad:GMButohUT ad requirements with adaptive power consumption. Time-domain, o f s simulations are shown to validate the presented approach.t ' WLAN. A complete top-down design procedure is described, putting special emphasis on optimizing the circuit design for I. INTRODUCTION different operation modes. To this purpose, different strategies The extraordinary growth ofwireless communication tech- are adopted at both architecture- and circuit-level in order t