ENG Resonators-Based Reconfigurable Microwave Filter for Stopband Frequency Diversity

In this paper, a reconfigurable microwave stopband filter is presented based on two different designs of ENG unit-cell. The resonant unit-cell structures are designed using a complementary patch in the shape of square and circle, each of which is surrounded by a thin complementary ring-type geometry. The overall size of the individual ENG unit-cell is 9×7.12 mm
²
which exhibit negative permittivity at 2.68 GHz and 2.42 GHz respectively. The stopband filter is implemented on Rogers TMM-13i substrate of relative permittivity ε
_r
=12.85 and height h=1.27 mm. The filter consists of unit-cells placed in the close vicinity of a 50 Ω microstrip line. In the proposed filter design, the count of ENG unit-cell resonators can be increased and selectively excited from 50 Ω microstrip line through PIN diodes to achieve diversity in the frequency of stopband transmission.