Design and Analysis of Ag- ${\rm Fe}_{3} {\rm O} _{4}$ Films as a Multi-Harmonic Suppressor in Wideband Bandpass Filters

This letter proposes a novel method of designing wideband bandpass filters (BPFs) that contain high-frequency harmonic suppression. Ag-Fe₃O₄ films are used as harmonic suppression materials in such filters to replace the current general suppressing circuits. The wideband BPF can be designed using distributed highpass filters are equipped with two short-circuited stubs, and Ag-Fe₃O₄ films are combined with the harmonic suppression mechanism. Several high-order harmonic resonance bands may be suppressed using a wide stopband by adjusting the thickness of the Ag-Fe₃O₄ films appropriately. The stopband of the proposed wideband BPF is extended to 20 GHz, which result in a rejection level higher than 15 dB.