FREQUENCY VARIABLE BAND STOP FILTER

摘要

PROBLEM TO BE SOLVED: To solve the problem that a conventional band variable filter increases a reflection amount at a pass band particularly when a frequency variable range is increased and increases a reflection amount in general at an attenuation band in the case of a band stop filter because the reflection characteristic of the pass band depends on a circuit comprising a fixed inductor and the inductor circuit is fixed while the resonance frequency of a resonance circuit varies when the center frequency is changed by switching of switching diodes. SOLUTION: A pair of identical circuits is configured to be a balanced type, each circuit comprising: two 3dB hybrids wherein a termination resistor is connected to an isolation terminal; two systems of transmission lines for interconnecting distribution/combination terminals of the two 3dB hybrids; and one series resonance circuit or more connected between each of the two systems of the transmission lines and a ground conductor and provided with a variable reactive element having a variable function of the resonance frequency. COPYRIGHT: (C)2005,JPO&NCIPI