Design of an active CMOS subharmonic mixer with enhanced transconductance

This paper presents a wideband Gilbert subharmonic mixer (SHM) that partly overcomes the fundamental trade-off between radio frequency (RF) and intermediate frequency (IF) currents. Compared to the conventional SHM, the proposed SHM features large gain, low noise figure (NF) and moderate linearity over a wide bandwidth by concurrent usage of regulated-cascode RF-stage and inductive connection between RF and LO stages. Numerical analyses along with circuit-level simulations are given to evaluate the performance of the proposed mixer and facilitate its optimum design. Simulations using a 0.18 μm RF-CMOS process demonstrate that the proposed mixer, at a fixed IF of 100 MHz, exhibits more than 5 dB and 2 dB improvements in conversion gain (CG) and NF, respectively.