Reconfigurable Band Stop Filter Using Slotted Elliptical Patch Resonator with Defected Ground

A frequency reconfigurable compact band stop filter derived from an elliptical patch resonator with orthogonal feed is presented in this paper. The proposed filter can be switched from a wide stop band to a dual stop band. The switching action is implemented using two PIN diodes connected in the ground plane. When the diodes are in the ON state, the filter acts as a dual band, band stop filter with centre frequencies at 1.85 GHz and 4.2 GHz and fractional bandwidth 70.6% and 24.6% respectively. When the diodes are in the OFF state, the filter acts as a wide band, band stop filter with a centre frequency at 2.77 GHz and fractional band width 95.45%. The prototype of the filter having dimension 0.74λg×0.84 λg (λg is the guided wavelength calculated for 50 Ω transmission line at 2.77 GHz) is fabricated on a substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. Measured results on realized prototype are provided to ensure the reliability of the proposed design.