Method of manufacturing a filter by forming strip lines on a substrate

Abstract

The present invention relates to a filter employed in a radio communication apparatus and has as an object to prevent characteristics of the filter from degradation by increasing unloaded Q of strip line resonators of the filter. For achieving the above object, the invention provides a filter which comprises a substrate (4) having first and second strip lines (5), (6) formed on a top surface and mutually coupled through an electromagnetic field and an earth pattern (2) on a bottom surface, respectively, a dielectric layer (8) laminated on the top surface of the substrate and having capacitor patterns (9), (10) formed on a top surface thereof in opposition to the aforementioned first and second strip lines (5), (6), and a metal cap (1) fitted over the dielectric layer (8) having an electrically conductive surface at least on one of top and bottom surfaces, and an electrically conductive film formed on a portion of an outer peripheral surface of the aforementioned substrate (4) and connected to the earth pattern (2) on the bottom surface thereof, wherein at least a portion of an outer periphery of the metal cap (1) in led downwardly toward the electrically conductive film, and the portion led downwardly is connected to the electrically conductive film.