Microwave filter application of inductively coupled superconducting striplines

A design theory is presented to apply inductively coupled superconducting striplines to microwave filters, in which the coupled stripline system is considered as four-port circuitry. By obtaining eigenvalues for impedance, admittance, and scattering matrices, the authors obtained general formulas for designing bandpass filters. The microwave filters using this coupling scheme are simple in design and have advantages of external-modulation capability. Experiments to demonstrate the validity of this coupling scheme have been performed in the frequency range between DC and 300 GHz by investigating the coupling between a Josephson oscillator and an external stripline.<
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