Miniaturized multiband matched band-stop filter

Multiple stop-bands are required in order to suppress interference in radio spectrum with multiple wireless systems operating in it. In addition, wireless communication systems usually require small devices to fulfill the miniaturization requirements and simplicity of mobile unit. As a result, this paper is to propose a novel miniaturized matched band-stop filter with high rejection level. This filter results in 50 % size reduction compared with the dual-mode ring resonator that has an electrical length of 360°. In addition for the short electrical length of this filter the first spurious resonance occurs at 4.7 times the fundamental resonance frequency. The filter design is cascaded to achieve multiband band-stop filter at center frequencies of 0.99 GHz and 1.04GHz. Theoretical analysis together with experimental results is presented to demonstrate the feasibility of the approach.