Y. Dong et al., A WAVE-GUIDE BANDPASS FILTER MADE OF HIGH-PERMITTIVITY CERAMICS, Electronics & communications in Japan. Part 2, Electronics, 77(1), 1994, pp. 46-56
A rectangular waveguide was formed with ceramics having a high relativ
e permittivity of 93. This waveguide is divided into two in the E-plan
e. This structure was used for the design and fabrication of a bandpas
s filter of small size and light weight which can be surface mounted.
Inductive strips are formed on the E-plane so that the center frequenc
y of the one-half wavelength resonator and the coupling coefficient be
tween the resonators are adjusted. Further, by choosing a structure in
which the filter is connected directly from a microstrip line, the st
ructure is miniaturized. In the design, first the dimension dependence
of the characteristic values of the composite resonators, e.g., the c
enter frequency and the coupling coefficient, was found experimentally
. Then a general filter theory was applied. Further, the characteristi
c values of the resonator were studied theoretically so that the dimen
sion dependence can be explained qualitatively.