Design Consideration for a Two-Distributed-Junction Tuning Circuit

  • Y. Uzawa
  • M. Takeda
  • A. Kawakami
  • Z. Wang
  • T. Noguchi


We describe a novel method of designing a tuning circuit with two half-wave distributed junctions separated by a half-wavelength microstripline, which analytically determines the circuit parameters such as the minimum current density of the junctions and the characteristic impedances of the distributed junctions and the microstripline. The tuning circuit was approximated by simple transmission theory and then simplified with ideal circuit components for analysis. We applied Chebyshev’s band-pass filter theory, in part, to optimize the circuit design. The analytical results revealed that a high characteristic-impedance ratio between the distributed junctions and the microstripline is necessary to obtain broadband matching using low-current-density junctions. The experimental results for all-NbN SIS mixers we designed with this method demonstrated double-sideband (DSB) receiver-noise temperatures of 6–10 quanta from 710 to 810 GHz for a mixer with a current density of only 4 kA/cm2 (estimated ωCJRN product of 37 at 750 GHz). The RF bandwidth was broader than that of a conventional full-wave distributed SIS mixer with the same current density.

Key words:

broadband tuning circuit SIS mixer Chebyshev’s filter submillimeter-wave low-current density 


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Copyright information

© Springer Science+Business Media, Inc 2005

Authors and Affiliations

  • Y. Uzawa
    • 1
  • M. Takeda
    • 1
  • A. Kawakami
    • 1
  • Z. Wang
    • 1
  • T. Noguchi
    • 2
  1. 1.Kansai Advanced Research CenterNational Institute of Information and Communications TechnologyKobeJapan
  2. 2.Nobeyama Radio ObservatoryNational Astronomical Observatory of JapanNobeyama, NaganoJapan

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