Design of compact monopole antenna with tunable characteristics using Active FSS

A monopole antenna having tunable operating band and high FBR (Front-to-back lobe ratio) has been proposed. The monopole antenna consists of a hexagonal shaped radiating patch and a rectangular ground plane on either side of FR4 epoxy dielectric substrate. The overall dimension of the monopole antenna is 20 mm * 20 mm. The simulated results indicate that the antenna initially covers a frequency band from 3.2 GHz to 7.2 GHz with peak gain of 1.6 dBi and peak FBR of 7.9. To achieve the tunable characteristics, two active FSSs are placed 15 mm below the antenna with 45°angle to the horizontal plane. When the FSSs are in on-state, the operating band shifted to the higher frequency band and the combined structure operates from 5.8 GHz to 7.5 GHz with peak gain of 6.3 dBi and peak FBR of 23.2. When the FSSs are in off-state, the single band characteristics of the antenna change into dual band characteristics (first band: 3.73 GHz-5 GHz and second band: 6.37 GHz-7.6 GHz). Thus, the proposed combination is useful for switching of reflection band as per requirement.