Superconducting 4–8 GHz IF Hybrid for Low Noise mm-Wave Sideband Separation SIS Receiver

Journal article, 2012

We present the design and performance of a superconducting 90 degree hybrid covering a full octave bandwidth from 4 to 8 GHz. The hybrid is designed using the Lange coupler layout. The novel features of this quadrature hybrid include superconducting niobium (Nb) transmission lines, air bridges to connect the fingers of the coupler and a bias-T integrated with the coupler. Our simulations indicate that the amplitude imbalance of the designed hybrid is less than 0.8 dB over the entire 4–8 GHz band with negligible phase imbalance.