A Wideband High Linearity and Low-Noise CMOS Active Mixer Using the Derivative Superposition and Noise Cancellation Techniques

Abstract

Using the derivative superposition and noise cancellation techniques, a high linearity, enhanced conversion gain, and low noise figure (NF) CMOS active mixer is presented for wideband applications. The third-order input intercept point (IIP3) of the proposed mixer is improved by cancelling the intrinsic second-order derivative transconductance (g ) of the main transistor. This is achieved by using an auxiliary transistor which is biased in the weak inversion region to create g with the same amplitude and opposite sign relative to the main transistor. A linear path consisting of two parallel transistors is utilized to cancel the thermal noise of the input transistors. A constant transconductance (Gm) bias circuit is employed to achieve robust performance against process, voltage and temperature variations. Detailed analysis of the proposed mixer is presented, and extensive simulation results are provided to evaluate the efficiency of the utilized techniques. The simulated mixer operates from 500 MHz to 3.1 GHz RF input frequency. Post-layout circuit-level simulation results using a 90-nm RF CMOS process with Spectre-RF reveal that the IIP3 and conversion gain of the proposed mixer are improved about 6.1 dB and 6.2 dB, respectively, compared to the conventional CMOS active mixer. Also, the NF of the proposed mixer is decreased about 2 dB. The simulated S11 is less than − 12 dB in whole RF range. It consumes 13.9 mW from a single 1.1 V power supply which is approximately 60% more than that of the conventional active mixer.