Dual‐stopband filter using metamaterial hexagonal mushroom resonator

In this article, dual‐stopband filter based on metamaterial hexagonal mushroom resonator is presented first time. Here, hexagonal mushroom resonators are used to synthesize planar microwave filter using the coupling coefficient approach based on frequency transformation. There are different approaches to implement dual‐band filters among which frequency transformation technique is advantageous than other methods in terms of complexity to find the transfer functions. So it is applied here to generate the coupling matrix of direct coupled dual‐stopband filter. For easy tuning, filter has been synthesized in cul‐de‐sac topology that is suitable for band stop filter realization and eliminates the need for diagonal couplings. Finally, a six‐pole direct‐coupled dual‐stopband filter in cul‐de‐sac configuration has been fabricated using hexagonal metamaterial mushroom resonator. Excellent agreement between simulation and experimental result has been achieved.