A novel dual-mode bandpass filter (BPF) using stub-loaded defected ground open-loop resonator is proposed in this article. Defected arrow-shaped stub is loaded to a defected ground open-loop resonator, and two non-degenerate modes are excited for dual-mode characteristics. Based on even- and odd-mode theory, dual-mode characteristics of the resonator is analysed. Design equations for the defected-ground resonator are investigated. A two-pole dual-mode bandpass filter operating at 2.4 GHz with fractional bandwidth of 7.97% is designed, fabricated, and measured. Good agreement between simulated and measured results verifies the validity of this design methodology.
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