Extreme Virtual Local Leakage Suppression in an Even Harmonic Quadrature Mixer with Anti-Parallel Gated Anode Diode Pairs

This paper describes an even harmonic quadrature mixer extremely suppressed virtual LO leakage. A mixer is used in a microwave generator for controlling and read out the states of the superconducting Quantum bit (Qubit), which requires low spurious for decreasing quantum error. The proposed Anti-Parallel Diode Pair (APDP) consisting of Gated Anode Diodes (GADs) provides very symmetrical layout, and it suppresses the virtual LO leakage and the other even order mixing products providing low distortion. A fabricated X band even harmonic quadrature mixer MMIC with the anti-parallel GAD Pairs achieved OIP3 of 1.3 dBm, even order mixing products of -59.2 dBc or less, and especially the virtual LO leakage suppression of 126.8 dB.