Flexible Baseband Analog Circuits for Software-Defined Radio Front-Ends

This paper presents a novel approach to design a digitally programmable low pass filter (LPF) and variable gain amplifier (VGA) intended for a software-defined radio (SDR) front-end. These flexible analog circuits are driven by a network-on-chip (NoC) that is able to set performance parameters like cut-off frequency, selectivity, noise, and gain guaranteeing at any time a near-optimal power/performance trade-off. A design approach is proposed to tackle the challenges imposed by flexibility in analog design. A silicon prototype is realized in 0.13-mum CMOS technology with 1.2-V supply voltage to prove the validity of the proposed solution. The LPF provides a frequency tuning range between 0.35 MHz and 23.5 MHz with an adaptive integrated noise level between 85 muVrms and 163 muVrms whereby the power consumption conveniently varies from 0.72 mW to 21.6 mW according to the required performance. The VGA is made up of two cascaded gain stages and provides a gain range from about 0 dB to 39 dB with a reconfigurable power/bandwidth.