Compact Dual-Band BPF Based on Quarter Wavelength SIR for WiMAX and WLAN Applications

This study presents a design procedure of microstrip bandpass filter based on quarter wavelength step impedance resonator (SIR). The frequency response of the proposed filter covers the 3.5 GHz worldwide interoperability for microwave access (WiMAX) band licensed by IEEE 802.16e and the 5.825 GHz wireless local area networks (WLANs) band licensed by IEEE 802.11a. Dual-band performance can be simply achieved in SIR by adjusting its electrical length and impedance ratios. Three transmission zeros with skirt shape response around the centers of the bands were achieved through proper coupling between ports and the resonator. Additional transmission zeros were introduced using stop band stubs, to enhance the out-of-the band rejection of the filter frequency response. CST microwave studio and SONNET full-wave electromagnetic simulator were used to validate the simulation results. The proposed filter can be widely used in wireless communication applications