PURPOSE: To realize space saving without necessitating a large amount of area, by laminating plural filter element assemblies in which a metallic foil pattern such as a copper foil, etc., is formed on a dielectric sheet in a strip line type microwave filter.
CONSTITUTION: An input line 4, resonance lines 6, 6, and an output line 5 are formed on the dielectric sheet 1 by conductive patterns, and the filter element assembly A is constituted of the dielectric sheet 1 and the conductive patterns, and those four filter element assemblies A ara laminated in four layers. Since an interval between the resonance lines 6, 6, or the input and output lines 4 and 5 is decided by the thickness of the dielectric sheet 1, a stable interval among the lines 4, 5, and 6 can be obtained by using the dielectric sheet 1 with required thickness. A filter characteristic between the input/output lines 4 and 5, and overlapped length among the lines 4, 5, and 6 in a thickness direc tion can be set at the 1/4 of a wavelength λg equivalent to the central frequency of a desired filter characteristic. Also, by thinning the thickness of the dielectric sheet 1, coupling among the lines 4, 5, and 6 can be strengthened, and insertion loss can be decreased.
FUJII YASUHIRO
KOMATSU MIKIO
