Dual band pass filter with sharp transmission zeros for wireless applications

Band stop/pass filters using octagonal and rectangular-shaped open loop resonators are proposed for wireless applications. The filter has the advantage of low insertion loss in the passbands and high return loss in the stopbands. The main idea of the filter is to achieve transmission bands by utilizing rectangular shape open loop resonators which are coupled to the input and output ports. The open loop resonators are used to generate stopbands in the filter response. The filter has small size, good response and the simulated results agree with the measured results. The lower insertion loss, and higher rejection band levels are investigated which confirm the suitability of the proposed dual BPF for WLAN and WiMAX applications.