The Path to the Software-Defined Radio Receiver

TLDR

A software‑defined radio receiver has emerged as a viable mobile handset concept after years of speculation. The receiver achieves this by electronically tuning a wideband front‑end that can receive a single channel of any bandwidth in any band, sampling the channel at zero IF with a flexible analog baseband, then applying clock‑programmable downsampling and filtering; a 90‑nm CMOS prototype demonstrates tuning from 200 kHz to 20 MHz across 800 MHz–6 GHz. This architecture delivers tunable selectivity surpassing traditional RF prefilters while keeping the conversion rate low enough for milliwatt‑level A/D conversion.

Abstract

After being the subject of speculation for many years, a software-defined radio receiver concept has emerged that is suitable for mobile handsets. A key step forward is the realization that in mobile handsets, it is enough to receive one channel with any bandwidth, situated in any band. Thus, the front-end can be tuned electronically. Taking a cue from a digital front-end, the receiver's flexible analog baseband samples the channel of interest at zero IF, and is followed by clock-programmable downsampling with embedded filtering. This gives a tunable selectivity that exceeds that of an RF prefilter, and a conversion rate that is low enough for A/D conversion at only milliwatts. The front-end consists of a wideband low noise amplifier and a mixer tunable by a wideband LO. A 90-nm CMOS prototype tunes 200 kHz to 20-MHz-wide channels located anywhere from 800 MHz to 6 GHz