An 8–10-GHz Low-Loss Image-Reject HTS Mixer Based on Cascaded Josephson Junctions

A 7.8–9.8-GHz low-loss high-
$T_{c}$
superconducting (HTS) image-reject Josephson junction mixer is presented in this letter. Image rejection is achieved using low-loss image rejection filters and a pair of parallel dual-mode resonators. Three cascaded Josephson junctions are monolithically integrated with impedance matching networks and bandpass/low-pass filters on a single chip for low loss and compactness. The implementation of series junction array increased the overall junction equivalent impedance, so that a better impedance matching is achieved. Measurement results of the novel HTS mixer showed a low conversion loss at 5.5 dB and an image-reject ratio over 30 dB within the desired frequency. The proposed cascaded junction configuration provides a new approach for impedance matching in HTS mixer designs, and the demonstrated mixer performance makes it an ideal candidate for
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-band radar systems.