Design of a Low-Loss Bandpass Filter Using Dielectric Rod Resonators Loaded in a High-Tc Superconductor Cylinder

Yoshinori KOGAMI  Yoshio KOBAYASHI  

IEICE TRANSACTIONS on Electronics   Vol.E75-C   No.8   pp.900-905
Publication Date: 1992/08/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Cryogenic Microwave Devices)
Category: Passive Devices
high-Tc superconductor,  bandpass filter,  dielectric resonator,  

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A Chebyshev type bandpass filter using four TM01δ-mode dielectric rod resonators oriented axially in a high-Tc superconductor cylinder is designed with 3 dB bandwidth 36 MHz at 11.958 GHz. The single resonator which contains a Ba (MgTa) O3 ceramic rod of εγ=24 and a YBa2Cu3Oy bulk cylinder is designed to realize temperature coefficient of f0, τf=0 ppm/K at 20 K. The unloaded Q, Qu measured at 20 K is 150,000 which is higher than Qu=100,000 for a TM01δ-mode resonator with a copper cylinder. When the constructed filter is cooled from room temperature to below 50 K, the center frequency shifted only 5 MHz which corresponds to τf=1.5 ppm/K and the insertion loss IL0 at the center freqency reduced from 3.0 dB to about 0 dB, the designed value of which is 0.04 dB, which is too small to be measured accurately.