A theoretical study has been undertaken to solve inter-resonator coupling problems, and to design a new structure of microwave bandpass filter. This filter is composed of quarter-wavelength resonators arranged in a housing with the same ends short-circuited. This arrangement of resonators has never been utilized to compose bandpass filters because of the small inter-resonator coupling. The coupling coefficient of TEM resonant lines has been derived theoretically and expressed with capacitive parameters of the coupled lines. The accurate values of capacitances of the lines were obtained by the numerical analysis of the TEM field. By a simple method to make the medium inhomogeneous through removing the dielectric partially, a simplified structure of filter has first been realized based on the theory. Through numerical analysis by the finite difference method, this structure is also shown to have higher unloaded Q of resonator than conventional dielectric-filled coaxial filters to minimize the volume of filters.
[1]
A. Fukasawa,et al.
Miniaturized Microwave Filter Construction with Dielectric-Loaded Resonator and Space Coupling
,
1981,
1981 IEEE MTT-S International Microwave Symposium Digest.
[2]
M. V. Schneider.
Computation of Impedance and Attenuation of TEM-Lines by Finite Difference Methods
,
1965
.
[3]
E.M.T. Jones,et al.
Coupled-Strip-Transmission-Line Filters and Directional Couplers
,
1956
.
[4]
S. Cohn.
Direct-Coupled-Resonator Filters
,
1957,
Proceedings of the IRE.
[5]
M. Dishal,et al.
Alignment and Adjustment of Synchronously Tuned Multiple-Resonant-Circuit Filters
,
1951,
Proceedings of the IRE.
[6]
Atsushi Fukasawa.
Composition and analysis of a new waveguide resonator filter with dielectric loading
,
1981
.