Design of a high linearity low noise mixer for low voltage application

A 1.2V Gilbert mixer with improved linearity and noise figure is presented. To improve the linearity, an optimum gate bias is applied to the transconductance stage, and a series LC network resonating around 2ƒ LO is implemented at the common source nodes of the switch quad. Analysis shows that the flicker noise performance also benefits from the series resonating network. The 2.1GHz mixer fabricated with 0.13µm CMOS technology is demonstrated. Linearity measurement from two tone tests shows that the IMD3 is improved over a wide range of the input power level. Compared with the conventional Gilbert mixer, the IMD3 is improved by 13.1dB and the DSB noise figure measured at 1MHz intermediate frequency is improved by 3.7dB. The mixer consumes 3.5mA current from a 1.2V supply voltage.