A 30 GHz 90-nm CMOS Passive Subharmonic Mixer with 15 GHz Differential LO

A new passive subharmonic mixer topology is presented and compared to a previously published passive topology. The comparison is conducted using simulations at 30 GHz with a 90-nm CMOS design kit. The advantage of the new passive subharmonic mixer is that it only requires a differential local oscillator (LO) signal, compared to the previously published mixer that requires a quadrature LO signal. The mixer consists of two cascaded passive mixers with an interstage second order filter suppressing harmonics while providing some 10 dB of voltage gain at the LO frequency. The noise performance of the differential mixer is slightly worse than for the quadrature one, with a simulated down conversion SSB NF of 10 dB compared to 7 dB. The voltage conversion gain is - 1 dB for both mixers, all with a 1 V LO amplitude.