Tri-band bandpass filter using stub loaded resonators

A tri-band bandpass filter using short and open stubs loaded resonators is presented. The first and the third passband frequencies of the tri-band filter can be flexibly controlled by tuning the lengths of the stubs, whereas the second passband frequency is fixed. A tri-band filter has been implemented with four transmission zeros, the filter has good tri-passband performance at 1.57, 2.4, 3.5 GHz measured results agree well with simulated ones.

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