Metamaterial based dual band bandpass filter design for WLAN WiMAX applications

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ABSTRACT This article proposes a dual‐band bandpass filter exhibiting negative effective magnetic permeability as well as effective negative electric permittivity. The proposed filter is constructed by loaded open‐loop resonators (OLR). Input and output ports are connected to each other with a grounded feedline having two via holes located at the tapping point alignments of loading elements. Dual‐mode properties of OLRs are used to obtain the dual‐band response. Hence, each passband can be controlled individually by means of the gap between the folded parts of the OLR and the dimensions of loading elements. Four loaded OLRs are placed at the upper and lower sides of the main feedline to obtain two poles in each passband. Center frequencies of the designed filter are adjusted to 2.45 GHz (WLAN) and 3.5 GHz (WiMAX). It has an electrical length of 0.414 λg × 0.32 λg, where λg is the guided wavelength at the lowest center frequency, 2.45 GHz. Proposed filter has also been fabricated for the experimental verification of the design methodology. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2211–2214, 2014