Analysis and Optimization of Direct-Conversion Receivers With 25% Duty-Cycle Current-Driven Passive Mixers

The performance of zero-IF receivers with current-driven passive mixers driven by 25% duty-cycle quadrature clocks is studied and analyzed. It is shown that, in general, these receivers outperform the ones that utilize passive mixers with 50% duty-cycle clocks. The known problems in receivers with 50% duty-cycle mixers, such as having unequal high- and low-side conversion gains, unexpected IIP2 and IIP3 numbers, and IQ crosstalk, are significantly lowered due to the operating principles of the 25% duty-cycle passive mixer. It is revealed that with an intelligent sizing of the design parameters, the 25%-duty-cycle-mixer-based receiver is superior in terms of linearity, noise, and elimination of IQ crosstalk.