AbstractA rectangular waveguide was formed with ceramics having a high relative permittivity of 93. This waveguide is divided into two in theE‐plane. This structure was used for the design and fabrication of a bandpass filter of small size and light weight which can be surface mounted. Inductive strips are formed on theE‐plane so that the center frequency of the one‐half wavelength resonator and the coupling coefficient between the resonators are adjusted. Further, by choosing a structure in which the filter is connected directly from a microstrip line, the structure is miniaturized.In the design, first the dimension dependence of the characteristic values of the composite resonators, e.g., the center frequency and the coupling coefficient, was found experimentally. Then a general filter theory was applied. Further, the characteristic values of the resonator were studied theoretically so that the dimension dependence can be explained qualitat