Design of a High Selectivity Quadband Bandpass Filter Based on Open Loop Stub Loaded Resonator for UMTS, WLAN, Wimax and ITU Applications

This paper presents high selectivity micro strip Quad band band pass filter Based on OLSLR (Open loop stub loaded resonator) for various wireless communication applications such as UMTS (Universal Mobile Telecommunication Systems) at 2.1GHz, WLAN (Wireless Local Area Networks) at4GHz, Wimax (Worldwide Interoperability For Microwave Access) at 6.2GHz And ITU (International Telecommunication Unions) at7.2GHz. Where pair of resonator is capacitiely coupled to each other and the feed lines. First and the third pass bands are generated by resonator A. The second and the fourth pass bands are excited by resonator B. The proposed technique provides sufficient degree of freedom to control the center frequency and bandwidth of the four pass bands by varying the dimensions of stub. In addition, six transmission zeros created around the pass bands results in a quad-band filter with high selectivity