Narrowband superconducting receiving filter for 9GHz-band weather radar

We have developed a high-temperature superconducting (HTS) receiving fillter with narrow bandwidth characteristic for 9 GHz band weather radar to reduce interference between adjacent radar channels. To realize a filter with a narrow bandwidth and low insertion loss is necessary to obtain high unloaded Q (Q_u) resonator. Coupled microstrip line resonators with 1.5 times wavelength and odd mode resonance frequency were adopted to suppress the radiation loss and achieve a high Q_u value. The developed HTS filter has 8-pole quasi-elliptic function response for sharp skirt characteristic. The measured frequency response of the developed filter shows center frequency of 9700 MHz, insertion loss of 1.8 dB, which agrees with the designed responses.