Artificial epsilon negative structure-inspired microwave bandstop filter for wide frequency diversity

This paper presents the development of a planar microwave bandstop filter using an artificially engineered epsilon negative (ENG) structure. The ENG structure consists of complementary square-horn ring geometry designed using a FR-4 substrate of 25 × 20 mm
²
. The measured notched frequency of the device transmission coefficient at 1.75 GHz closely matches with the simulation result. The lumped response of the device was modified by properly biasing two PIN diodes and one varactor diode over the complementary gap in the structure. This technique has been used to achieve frequency diversity in the spectrum of 0.6-3.5 GHz.