A 2.4-GHz subthreshold down-conversion mixer with improved noise figure

In this paper, a broadband low noise subthreshold mixer in 0.18 μm-CMOS, based on double balanced Gilbert cell is presented. Low noise figure and high conversion gain at wide bandwidth frequency range are two important factors of broadband mixers. All transistors in this design are biased in subthreshold region in order to suppress mixer noise figure. Also, a static current injection circuit (current bleeding circuit) is used to improve its noise performance. The peaking inductor has been utilized to improve mixer gain performance. Simulation results of designed mixer show excellent performance of noise and gain. It achieves a maximum conversion gain of 22.4 dB and an average single-sideband noise figure of 8.4 dB at 5 GHz bandwidth. Circuit consumption power is 16 mW at 1.8V supply voltage.