PLANAR FILTER, DUPLEXER USING THE SAME, HIGH FREQUENCY MODULE USING THEM AND COMMUNICATIONS EQUIPMENT USING THE MODULE

摘要

PROBLEM TO BE SOLVED: To provide a planar filter where an attenuation pole can be formed near the low area of a pass band. SOLUTION: Two quarter-wave strip line resonators 11 and 13 are arranged on both sides across a half-wave strip line resonator 4. The opening end sides are arranged near the two different opening ends of the half-wave strip line resonator 4. Ground end sides are bent to the directions of the half-wave strip line resonator 4 at nearby parts of the center of the half-wave strip line resonator 4 and ground ends are mutually counterposed. Thus, an attenuation pole is installed near the low area side of a pass band and the attenuation characteristic of a plane filter can be improved.