Design of a Reconfigurable Mixer for Multi-Mode Multi-Standard Receivers

Abstract

This paper reports a reconfigurable wideband passive mixer for direct conversion multimode multi-standard receivers. Different from the traditional current-commutating passive mixers, transconductor stage of this design is variable. And the TIA stage is a second-order low-pass transimpedance amplifiers based on Tow-Thomas biquad topology, working as a current mode filter. The mixer is controlled by a 4-bit control word to realize the flexible gain and variable intermediate frequency bandwidth. Other characteristics such as power consumption, NF, and linearity is also reconfigurable according to different communication standard. Circuit is implementing in 0.18μm CMOS technology. Post-simulation results show that, with the radio frequency ranges from 700 MHz to 2.6 GHz, it provides four voltage conversion gains (10/16/22/28dB) and three-3 dB intermediate frequency bandwidth (5/7.5/10MHz). Under the maximum gain, the double sideband NF of the mixer is 8.4 dB. And under the minimum gain, IIP3 is 13 dBm. The chip occupies an area of 0.248 mm2 and drains a current of 8.5mA from a 1.8 V supply when the mixer has highest gain.