In this band-pass filter some dielectric resonators are lined up in a row. There are two metal cylinders whose respective length is about equal to one quarter wavelength of the base frequency (the central frequency of the band-pass filter). These two cylinders are laid out as follows: One is located between the input connector and the dielectric resonator at one end of the row of the resonators mentioned above. Another is located between the output connector and the dielectric resonator at another end of the row. Thus, various parasitic oscillation transmissions, especially the one at the double-base frequency, can be suppressed. |