A linearization technique for radio frequency CMOS Gilbert-type mixers

This paper demonstrates a linearization technique for radio frequency (R-F) CMOS Gilbert cell-based mixers. The main idea is to replace the simple differential pair of the basic mixer with a cross-connected one. When one specific design condition (also determined in the paper) is fulfilled, the third-order harmonic of the output signal is canceled, causing a major improvement of the third intercept point (IP3) of the mixer. In practice, the maximal achievable IP3 is limited by mismatches and models simplifications. Simulations results of the proposed circuit (using SpectreRF and the 0.35μm CMOS AMS technology) show an IP3 improvement of ∼8dB (5.25dBm comparing to -3dBm of the classical Gilbert cell). Our approach is very attractive because it necessitates only a small increase in the bias current 1.125mA vs. 1 mA and input capacitance - 1.5_Gilbert vs. C_Gilbert, and is feasible for use in multi-standard receivers.