Introduction

With the ever-increasing demand for instant access to data over wideband communication channels, the quest for a universal mobile terminal capable of delivering the ultimate user experience has become imperative. Over the last decade, researchers were exploring the possibility of having a universal radio that can be programmed and reconfigured through software to operate on any bands, channel bandwidths, and modulations. Such a universal radio was named software-defined radio (SDR) [1–6]. The SDRs face unique challenges because their targeted applications are mostly in mobile handheld devices. They must be small and affordable, and must last longer between charges. The design of such a low-cost, low-power, and flexible radio that meets the tough requirements of individual standards is enormously challenging and was and still is a hot topic of research for circuit designers as well as system and hardware engineers. One common yet relatively simple example of an SDR is a 3G cell phone, which can support as many as 17 bands in three modes of operation, namely GSM, EDGE, and WCDMA/HSPA.

The most aggressive SDR architecture was proposed by Mitola in 1995 [1], and is shown in Fig. 1.1(a). The only analog blocks in the receiver and the transmitter are an ADC and a DAC, respectively. Such a transceiver provides maximum flexibility through the digital signal processor (DSP), and it is even capable of simultaneously detecting several standards.