Design of Low-Voltage Broadband Folded Blixer for SDR Application

Abstract

Recent years, a large number of researches have been made on the software-defined radio (SDR) architectures. SDR is radio communication systems where typical functions have been implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are replaced by processing of software on a computer or embedded system [1]. A basic SDR system will consists of an analog-to-digital converter, preceded by a so called RF (radio frequency) front end. Large amounts of signals will be processed by the software processor instead of being handled in special designed hardware. Such architectures raises requirement for a very broad bandwidth even UWB (ultra-wideband) processed by a single receiver front end, covering the frequency range from hundreds MHZ to several or even tens of GHz [2]-[4]. However, the demands for linearity, noise figure or voltage gain still exists, making the requirement of broadband an even challenging topic. In this paper, a new structure for SDR front end application will be proposed. With balun LNA (low noise amplifier) combined with a folded mixer, the new structure will deal with a very wide input signal bandwidth ranging from 500 MHz to 6 GHZ and output directly at IF band from 5MHz to 300MHz. Design and topologies are chosen to best meet the input matching lower than -10 dB; overall font end noise figure lower than 8 dB; voltage gain as high as 25 dB.