Experimental Astronomy

, Volume 33, Issue 1, pp 225–236 | Cite as

Superconducting filter for radio astronomy using interdigitated, capacitively loaded spirals

  • Pietro Bolli
  • Frederick Huang
Original Article


A matched pair of microstrip spiral superconducting filters with centre frequency 357.5 MHz and 29.4% bandwidth has been developed for radio astronomy. The high coupling coefficients required for the large bandwidth have been achieved through interdigitating the spirals to provide a large interaction length, and by adding loading capacitors on the inner ends of the resonators, together with previously reported features. A low-pass filter has been cascaded with each band-pass filter to mitigate spurious responses. Measurements show 0.09 dB loss, thought to arise mainly from sources outside the filter itself, plus 0.12 dB maximum ripple.


Astronomy receiver design Computer-aided design High-Tc superconducting thin-film filters Microwave filters 



The authors acknowledge the help of Prof. Michael Lancaster of the University of Birmingham and Dr. Alessandro Navarrini of the INAF—Osservatorio Astronomico di Cagliari for making this research project possible.


  1. 1.
    Belohoubek, E., Kalokitis, D., Fathy, A., Denlinger, E., Pique, A., Wu, X.D., Green, S.M., Venkatesan, T.: High temperature superconducting components for microwave systems. Appl. Superconductivity. 1, 1555–1573 (1993)CrossRefGoogle Scholar
  2. 2.
    Grueff, G., et al.: Sardinia Radio Telescope: the new Italian project. In: Proc. SPIE Ground-based Telescopes, vol. 5489, pp. 773–783. (2004)
  3. 3.
    Huang, F.: Ultra-compact superconducting narrowband filters using single-and twin-spiral resonators. IEEE Trans. Microwave Theor. Tech. 51, 487–491 (2003)ADSCrossRefGoogle Scholar
  4. 4.
    Huang, F.: Superconducting spiral wide band-pass filters with wide upper stop-band. IEEE Trans. Microwave Theor. Tech. 53, 2335–2339 (2005)ADSCrossRefGoogle Scholar
  5. 5.
    Huang, F.: A narrowband superconducting filter using spirals with a reversal in winding direction. IEEE Trans. Microwave Theor. Tech. 54, 3954–3959 (2006)ADSCrossRefGoogle Scholar
  6. 6.
    Huang, F.: Dual-band superconducting spiral filters including narrow band-stop notches. IEEE Trans. Microwave Theor. Tech. 57, 1188–1195 (2009)ADSCrossRefGoogle Scholar
  7. 7.
    Ma, Z., Sakurai, E., Kobayashi, Y.: Design and measurement of a miniaturized HTS filter using microstrip spiral resonators. IEICE Trans. Electron. E88-C, 216–220 (2005)CrossRefGoogle Scholar
  8. 8.
    Matthaei, G., Young, L., Jones, E.M.T.: Microwave filters, impedance-matching networks, and coupling structures. Artech House, Norwood, MA, pp. 100, 432 (1980)Google Scholar
  9. 9.
    Ong, C.K., Chen, L., Lu, J., Tan, C.Y., Tan, B.T.G.: High-temperature superconducting bandpass spiral filter. IEEE Microw. Guided Wave Lett. 9, 407–409 (1999)CrossRefGoogle Scholar
  10. 10.
    Su, H.T., Huang, F., Lancaster, M.J.: Compact quasi-lumped element HTS microstrip filters. In: 2001 IEEE MTT-S Dig. 1985–1988 (2001)Google Scholar
  11. 11.
    Tofani, G., et al.: Status of the Sardinia Radio Telescope project. In: Proc. SPIE Ground-based and Airborne Telescopes II, vol. 7012. (2008)
  12. 12.
    Valente, G., Pisanu, T., Bolli, P., Mariotti, S., Marongiu, P., Navarrini, A., Nesti, R., Orfei, A.: The dual-band L-P feed system for the Sardinia Radio Telescope prime focus. In: Proc. SPIE Millim. Submillim. and Far-Infrared Detectors and Instrum. for Astronomy V, vol. 7741. (2010)
  13. 13.
    Yu, T., Li, C., Li, F., Zhang, Q., Sun, L., Gao, L., Wang, Y., Zhang, X., Li, H., Jin, C., Li, J., Liu, H., Gao, C., Meng, J., He, Y.: A wideband superconducting filter using strong coupling resonators for Radio Astronomy Observatory. IEEE Trans. Microwave Theor. Tech. 57, 1783–1789 (2009)ADSCrossRefGoogle Scholar
  14. 14.
    Zhang, G., Huang, F., Lancaster, M.J.: Superconducting spiral filters with quasi-elliptic characteristic for radio astronomy. IEEE Trans. Microwave Theor. Tech. 53, 947–951 (2005)ADSCrossRefGoogle Scholar
  15. 15.
    Zhang, G., Lancaster, M.J., Huang, F., Roddis, N.: An HTS wideband microstrip bandpass filter for L band receivers in Radio Astronomy Observatory. In: Proc. 37th European Microw. Conference, pp. 450–453 (2007)Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  1. 1.Astronomical Observatory of CagliariNational Institute for AstrophysicsCapoterraItaly
  2. 2.School of EECEUniversity of BirminghamEdgbastonUK

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