Band-pass filter and communication apparatus

摘要

A band-pass filter includes electrodes formed on both upper and lower surfaces of a dielectric plate, and a plurality of non-electrode portions on the upper and lower surfaces of the dielectric plate so that the non-electrode portions face each other across the dielectric plate to form resonators in regions confined by the non-electrode portions on the dielectric plate. The resonators other than at least input- and output-stage resonators are nlambd/2 resonators, where lambd denotes one wavelength and n is an integer more than one. The first- and second-stage resonators, and the third- and fourth-stage resonators are magnetically (inductively) coupled, and the second- and third-stage resonators are capacitively or inductively coupled. The band-pass filter therefore provides satisfactory attenuation characteristic from the pass band to the stop band, and can also be compact and lightweight.