Distortion in Current Commutating Passive CMOS Downconversion Mixers

CMOS passive mixer linearity is analyzed using a Volterra-series analysis and closed-form expressions for IIP
₂
, two-tone IIP
₃
, and cross-modulation IIP
₃
are presented, exhibiting dependence upon the mixer source and load impedances. Design guidelines are suggested for improving the mixer linearity performance. Accurate expressions are presented for the input impedance of an ideal passive mixer with an arbitrary load impedance. The calculations are in close agreement with the measured results and the simulated response.