Gilbert-Cell Mixer for WiMAX Applications

Differential implementation is becoming highly popular in Radio Frequency Integrated Circuit (RFIC) design, notably for its high immunity to common-mode noises, acceptable rejection of parasitic coupling, and increased dynamic range. One RF front-end building block that is usually designed as a differential circuit is the mixer. This paper presents a design, study, and optimization of a differential mixer, more specifically the Gilbert-cell mixer (also known as double-balanced mixer) implemented on a direct-conversion architecture in a standard 90 nm Complementary Metal-Oxide Semiconductor (CMOS) process. Operating frequency is set to 5GHz, which is a typical frequency for Worldwide Interoperability for Microwave Access (WiMAX) receiver. Impedance matching was necessary to design and fully optimize the mixer design. The direct-conversion Gilbert-cell mixer design ultimately achieved conversion gain of 11.463dB and noise figure of 16.529dB, comparable to mixer designs from past research and studies.