A new super compact ultra-wideband (UWB) bandpass filter (BPF) with triple-notched bands is presented in this paper. Firstly, a new square ring quad-mode resonator (SRQMR) is employed to obtain the initial UWB BPF. Then, a triple-mode stepped impedance resonator (SIR) is inserted into the initial UWB BPF to achieve three desired notched bands. The proposed triple-mode SIR is found to have the advantages of introducing triple-notched bands and provide a higher degree of freedom to adjust the resonant frequencies. To validate the design concept, a new super compact UWB BPF with triple-notched bands respectively centered at frequencies of 3.7 GHz, 5.2 GHz and 7.8 GHz is designed and measured. The predicted results are compared with measured data, and good agreement is reported.
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