A compact microstrip triple-band bandstop filter with rectangular meandered SIR for WiMAX applications

This paper presents a microstrip triple-band bandstop filter realized using tri-section meandered-lines stepped impedance resonator with a length equal to quarter wavelength (λ/4) to operate at stop bands of 2.42 GHz, 6.47 GHz, and 10.30 GHz. A drastic reduction in size of the filter was achieved by taking advantage of a simplified architecture based on meandered-line stepped impedance resonator. To increase bandwidth of each stop band, the two shunt connected structures are employed with a microstrip transmission line. Furthermore, an equivalent circuit model of the proposed filter is developed to matches well by the electromagnetic simulations. The return losses of the fabricated filters are measured to be -26.34, -23.52, and -18.58 dB while the insertion losses are -0.41, -0.55, and -1.87 dB at the respective stop bands.