A high isolation linear folded mixer for WiFi applications

A 2.4GHz novel RF Mixer with folded structure designed in 180nm RF-Mixed signal technology has been investigated. It is implemented by using double balanced transconductance switch (GmSw) configuration. The proposed mixer converts incoming signal to small signal RF current followed by PMOS current mirror structure. The circuit is designed and optimized such that it can operate at less than 1.8V of power supply. This paper proposes a design which focuses on the isolation between mixer ports. The high isolation achieved by incorporating folded structure with CMOS LO stage. In addition to that, the Mixer Common Mode Rejection Ratio (MCMRR) for the proposed folded mixer is defined in this paper. The post layout simulation has achieved 5 dB of conversion gain and 9 dBm third order input intermodulation product (IIP3). The highest isolation between LO-IF, RF-IF and LO-RF observed were up to 69 dB, 55 dB and 86 dB respectively.