compact triple notched bandpass filter based on multimode resonator

This paper presents a novel approach to design a miniaturized ultra-wideband (uwb) microstrip bandpass filter (bpf) with triple notched bands using a multimode resonator (mmr). the mmr is integrated with folded high-impedance interdigital coupled-line structures, enabling the filter to achieve a uwb characteristic while offering independent control over the introduced notched bands to prevent interference with other operating systems. additionally, the adoption of folded interdigital coupled-line structures significantly reduces the overall dimensions of the filter. the lc equivalent circuits and transfer function of the proposed mmr are extracted to analyze the behavior of the filter. to validate the design, a fabricated prototype of the proposed filter with triple notched bands at 5.4, 8.1, and 10.1 ghz, featuring attenuations exceeding -22 db, is presented. the measured results demonstrate that the designed filter provides a passband ranging from 4.2 to 12 ghz, along with a wide rejection bandwidth of up to 20 ghz.