Band-pass filter and communication apparatus

摘要

A band-pass filter includes electrodes (2, 3) formed on both upper and lower surfaces of a dielectric plate (1), and a plurality of non-electrode portions (4a, 4b, 4c, 4d) on the upper and lower surfaces of the dielectric plate (1) so that the non-electrode portions (4a-4d) face each other across the dielectric plate (1) to form resonators in regions confined by the non-electrode portions on the dielectric plate (1). The resonators other than at least input- and output-stage resonators are n lambda /2 resonators, where lambda 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. <IMAGE>