A compact dual‐band bandstop filter using a circular, folded, symmetric, meandered‐line, stepped‐impedance resonator

Abstract

Abstract This letter describes the implementation of a dual‐band bandstop filter based on a circular, folded, symmetric‐type, two‐section, meandered‐line, stepped‐impedance resonator (SIR), resonating at f 1 = 3.17 GHz and f 2 = 8.50 GHz. The length of each section of meandered‐line is equal to 0.30 and is 0.60 times the guided wavelength (λ g ), which can be properly tuned to control the first and second resonant frequencies. The attenuation level of the signal at 5.83 GHz can be increased by the proper placement of transmission zero, which ultimately helps to generate a controllable ultrawide stop band bandwidth. This filter reached an attenuation level of 32.75 and 26.21 dB with insertion losses of 0.43 and 0.39 dB at the respective stop bands. The size of the filter was drastically reduced using a simplified architecture as a circular, folded, meandered‐line, SIR. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2298–2301, 2014