Compact bandstop filter using triangular metamaterial mushroom resonators

In this paper, a triangular mushroom structure is proposed to realize stopband filter which gives significant reduction in size compare to other conventional resonators. It is found very interesting that in mushroom structure, resonance frequency can be changed by changing the position of the metallic via. Full wave EM simulations have been performed to calculate the coupling coefficients of coupled resonators. Finally a circuit and EM simulations has been done to design a direct coupled bandstop filter centered at 7.4GHz with design rejecting bandwidth of 700 MHz. To validate the experimental results, the filter is fabricated on a RT Duroid substrate 6010 with thickness of 1.27mm. The attractive feature of metamaterial resonator is its compact size which is reduction of 57% compared to the conventional resonator. The size of filter is 25 mm × 15 mm × 1.27 mm. The bandstop specifications are chosen specially for Wimax applications.