Design of edge coupled open loop metamaterial filters

Metamaterials with negative index of refraction has created great opportunities for novel applications at Radio Frequency. Metamaterial finds applications as filters, diplexers and as frequency selective surfaces for gain enhancement in antennas. In this work open loop filters with circle, triangle and pentagonal geometries are proposed which can be configured as metamaterial for various wireless applications. These metamaterials can be energised using different feeding mechanisms like edge coupling, electromagnetic coupling, inductive coupling, capacitive coupling etc. Proposed filters are energised using edge coupled feeding mechanism which has reduce complexity compared to other techniques. Edge coupling also ensures the tunability of the filters and make them applicable for low frequency, where the conventional planar filters consumes large area. The geometrical variations in the loop are found to influence the filter characteristics and this is studied in detail. Design equations are furnished for the filters based on the extensive analysis carried out using ANSYS High Frequency Structure Simulator (HFSS) using finite element method. The current distribution and electric field of the proposed filters are also analysed in detail. Filter prototypes with optimum performance as seen in the simulations are fabricated and measured using Keysight ENA 5080A Network Analyser. Good agreement is found to exist between experimental results and the simulated results for the designed filters. A comparative study is carried out based on the frequency of operation, bandwidth and the attenuation of the three designed filters among themselves and the previous works that authors referred into.