RESUMO
Differential approach is becoming highly preferred in radio frequency integrated circuit (RFIC) design due to its advantages, particularly its high immunity to common-mode noises, satisfactory rejection of parasitic coupling, and increased dynamic range. One particular RF front-end building block that is often designed as differential circuit is the mixer. This paper presents a study and design of a differential mixer, particularly the double-balanced mixer implemented on a zero-IF (zero-intermediate frequency) or direct-conversion architecture in a standard 90 nm complementary metal-oxide semiconductor (CMOS) process operating at frequency of 5 GHz, which is a typical frequency for worldwide interoperability for microwave access (WiMAX) receiver. Impedance matching was necessary to fully optimize the mixer design. The zero-IF double-balanced mixer design achieved conversion gain of 11.46 dB and noise figure of 16.53 dB, comparable to other mixer designs.