Filter having directional coupler and communication device

摘要

An inner conductor (1) comprising high impedance portions (1a) and low impedance portions (1b) alternately connected to each other is disposed in the center of an outer conductor (2) having a substantially square cross-section. Two holes (8) are formed in one side (upper surface in the drawing) of the outer conductor (2) so as to extend through the wall of the outer conductor (2). A substantially pi-shaped coupling line (5) comprising a main line portion and probe-connecting portions is formed on the surface of a dielectric substrate (3). Probes (4a,4b) made of conductor rods are connected at the ends, respectively. A resistor (6) is provided at one end of the main line of the coupling line (5). The other end of the main line functions as an output terminal (20), and can be connected to an external circuit. The probes (4a,4b) are inserted through the holes (8). The dielectric substrate (3) is disposed inside of the outer conductor (2) at predetermined positions.