Chapter 10
Reduced External Hardware and Reconfigurable RF Receiver Front Ends for Wireless Mobile Terminals
10.1 INTRODUCTION
To support software-defined radio (SDR), the radio-frequency (RF) receiver front end has to be “multi-band, multi-mode” capable. To achieve a multi-band RF receiver, band-specific external RF preselect and interstage filters form a major bottleneck. In this chapter, high-dynamic-range RF front ends that do not need an interstage external filter are shown. It is, however, extremely challenging to design a receiver front end without an RF preselect filter. Some design directions that could potentially achieve RF preselect filter elimination are discussed.
To achieve a multi-mode RF front end, the design needs to have programmable performance based on the wireless standard being received to accommodate the blocking and intermodulation scenarios, signal bandwidths, and other factors that are different between standards. A direct conversion–based W-CDMA (wideband code-division multiple access) and EDGE (enhanced data rates for global evolution) dual-mode receiver scenario is used to illustrate the multi-mode concepts. The system calculations for a W-CDMA RF receiver are discussed as the first step toward elimination of an interstage filter in a W-CDMA receiver so that the hardware can be reused for EDGE. Further, the design of high-performance RF circuit blocks with digitally programmable performance is detailed. ...
