FILTER, ANTENNA MULTICOUPLER AND COMMUNICATION UNIT

摘要

PROBLEM TO BE SOLVED: To obtain a filter that can control a relation between a pass band and an attenuation band and an antenna multicoupler and a communication unit. SOLUTION: The filter 1 consists of a one-stage trap filter 3 that is electrically connected to a 3-stage band pass filter 2 via a coupling capacitor C4. The trap filter 3 has a series resonance section 5 consisting of a resonator R4 and a resonance capacitor C8. A series circuit consisting of a capacitive reactance element (capacitor) C10, of an inductive reactance element (inductor) L10that respectively substantially nullify the admittance of the trap circuit and of a PIN diode D5 being a switching element is connected in parallel with the series resonance section 5.