Properties of Step-Edge Microbridge Josephson Junction Mixer Fabricated by YBaCuO Thin Film

The conversion efficiency and minimum detection power of a step-edge microbridge Josephson junction mixer (SEJJ mixer) were evaluated for both fundamental mixing and harmonic mixing. The SEJJ was fabricated by a YBaCuO thin film and all of the circuits inside the mixer were made from microstrip line circuits in order to reduce the microwave propagation losses. The conversion efficiencies (η) were -31 dB, -46 dB and -53 dB for fundamental mixing, second harmonic mixing and third harmonic mixing, respectively. The dependence of η on the harmonic number (N) was expressed as η\proptN -4.6 for N≦3. The minimum detection power (MDP) of -60 dBm (1.0 nW) was obtained in fundamental mixing, with a linear dynamic range of more than 40 dB.