Tri-Band Bandpass Filter Using Open Loop Resonator Loaded by One Stub with Three Branches

Abstract

To obtain an adjustable passband filter, one open stub with three branches is loaded on an open loop resonator. The first and the third passband frequencies of the tri-band filter can be flexibly controlled by tuning lengths of three branches, whereas the second passband frequency is fixed. The fabricated filter has good tri-passband performance at 2.19, 4.26, 6.30 GHz. Measured results agree well with the simulated ones.