IIP3 Enhancement of Subthreshold Active Mixers

This brief presents a modified subthreshold Gilbert mixer that includes an inductor between the drain of the radio frequency (RF) transistor and the sources of the LO transistors, an inductive source degeneration for the RF transistor, and a cross-coupling capacitor between the source of the RF transistor and the drain of the RF transistor in the other mixer branch to improve third-order distortion characteristics. This linearization technique enables a third-order intermodulation intercept point (IIP3) improvement of at least 10 dB compared to other subthreshold mixers. A 2.4-GHz mixer was designed and simulated using 0.11-mu m CMOS technology. In the typical corner case of the postlayout simulations, the linearized mixer achieves 6.7-dBm IIP3, 8.6-dB voltage gain, and 19.2-dB single-sideband noise figure with a low power consumption of 0.423 mW.