Multi-Mode / Multi-Band RF Transceivers for Wireless Communications

Chapter 6

ADCs and DACs for Software-Defined Radio

MICHIEL STEYAERT, PIETER PALMERS, and KOEN CORNELISSENS

Katholieke Universiteit Leuven, Leuven, Belgium

6.1 INTRODUCTION

The analog-to-digital converter (ADC) in the receiving (RX) path and the digital-toanalog converter (DAC) in the transmitting (TX) path of a transceiver form a bridge between the analog front end and the digital signal processor (DSP) at the back end. Consequently, they are indispensable in any modern communication system. The shift to multi-mode transceivers increases their importance even further. A softwaredefined radio (SDR) system should be able to handle any modern communication standard. This should be achieved by reconfiguring the transceiver with software. This means that the settings and performance of the transceiver can be changed without a need for additional hardware. In an SDR system, the ADC and DAC should be fast and accurate enough for each communication standard. Moreover, due to the flexibility requirements of the multi-mode transceiver, the analog front end is often simplified, leading to tougher specifications for the ADC and DAC. As wireless systems are mostly battery operated, the power consumption of the ADC and DAC should be minimized.

Furthermore, technology scaling can result in more difficult specifications for the ADC and DAC. The drive behind technology scaling is the fact that each step makes digital signal processing cheaper and cheaper. However, this is not true for analog signals. ...