An Improved High Linearity Active CMOS Mixer: Design and Volterra Series Analysis

Abstract

The linearity and noise requirements in multistandard applications make the design of mixers so challenging. In this paper a new highly linear CMOS mixer is proposed that utilizes second- and third-order distortion cancellation mechanisms using second harmonic injection technique, also an in-depth analysis of the mixer is presented too. The proposed circuit can work for wide channel bandwidth applications. Full Volterra series analysis of the transconductance stage of the proposed mixer is reported to show the effectiveness of the injection technique. The analysis of the mechanisms responsible for generating the fundamental tone, the second- and the third-order intermodulation distortions in the switching stage along with an LC filter is also reported. Simulations using TSMC 0.18 μm CMOS model technology demonstrate that IIP3 and IIP2 of the proposed mixer have 10 dB and 26 dB improvements in comparison with the conventional Gilbert-type mixer while the NF doesn't change significantly. The mixer achieves a conversion gain of 15 dB from a 1.8 V supply. The additional circuits used for the IM2 and IM3 cancellation mechanisms have a total current consumption of less than 1 mA.