The mixer is a crucial circuit block in a WiMax system receiver. The performance of a mixer depends on three specifications: conversion gain, linearity and noise figure. Many mixers have been recently proposed for UWB and wideband systems; however, they either cannot achieve the high conversion gain required for a WiMAX system or they are prone to high power consumption. In this paper, a folded mixer with a high conversion gain is designed for a 2-11GHz WiMAX system and it can achieve a 20MHz IF output signal. From the simulation results, the proposed folded mixer achieves a conversion gain of 18.9 to 21.5dB for the full bandwidth. With a 0.2 to 4.4dBm IIP3, the NF is 13.5 to 17.6dB. The folded mixer is designed using TSMC 0.18µm CMOS technology. The core power consumption of the mixer is 11.8mW.

A current folded mixer achieving low 1/f noise for low power direct conversion receivers is proposed. The proposed mixer topology decouples the design tradeoffs between noise figure, conversion gain and third order intermodulation distortion. Comparisons with the conventional current-reuse injection topology, the current folded mixer with 1/f noise minimized shows significant improvements. Experimental design on 2.4-GHz band and with 0.18-µm CMOS technology has revealed the advantages of the newly proposed topology.