A bandpass filter (BPF) is presented for ultra-wideband (UWB) applications with a notched band to reject the unwanted signals from the wireless local area network (WLAN) systems. The proposed UWB BPF consists of two pairs of open-loop resonators on the top layer and one coupled resonator on the bottom layer. The rejection band is introduced by adding an asymmetric open-loop resonator to two outer arms of open-loop resonators. The bandpass filter is designed to be operated within full bandwidth of 3.1 to 10.6GHz and to eliminate the WLAN signals of 5.8GHz. The suppression at 5.8GHz is larger than 15dB. The proposed configuration is proved to be both simple and compact.
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3. Singh, P. K., B. Sarbani, and Y.-H.Wang, "Planar ultra-wideband bandpass filter using edge coupled microstrip lines and stepped impedance open stub," IEEE Microwave Wireless Compon. Lett., Vol. 17, 649-651, 2007. doi:10.1109/LMWC.2006.890467