Chapter 3

Adaptive Multi-Mode RF Front-End Circuits

ALEKSANDAR TASIC

Qualcomm, San Diego, California

3.1 INTRODUCTION

To provide various services from different wireless communication standards with high capacities and high data rates, integrated multi-functional wireless devices are required. In the current multi-standard scenario of portable wireless systems, transceivers are mostly implemented by replicating the radio-frequency (RF) front end for each operating standard and by sharing partially the analog baseband circuitry, but with the aid of a number of additional switches. Although this approach allows for an optimal performance optimization across the bands, the increase in hardware required to implement such a multifunctional wireless device increases the total silicon area and cost and may reduce the use time compared to single-standard implementations.

By sharing building blocks between different applications and standards, portable wireless devices potentially gain advantage over existing devices: They use a smaller chip area and have a potential for lower overall cost. This requires the development of adaptive circuits and systems that are able to trade off power consumption for performance on the fly. Realization of adaptivity functions requires scaling of current consumption to the demands of the signal processing task [1]. The design implementation of such an adaptive front-end circuit is presented later in the chapter.

In the following section we outline the application ...

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