Beamwidth Control of Omnidirectional Antenna Using Conformal Frequency Selective Surface of Different Curvatures

Development and implementation of different curvatures of a conformal frequency selective surface (FSS) for achieving beam diversity in a dual-band monopole antenna are demonstrated. The FSS based on a flexible dielectric substrate (polymer) is reflective at 3.5 GHz. The curved FSS when incorporated in the antenna gives different beamwidths (3 dB) between 68°-130° for concave shape and 144°-210° for convex shape at 3.5 GHz. In both the cases, omnidirectional radiation from the antenna is maintained at 5.8 GHz. Later, a corner reflector based on the FSS instead of a metal, operating at 5.8 GHz, is integrated in the antenna along with the convex shaped curved FSS. The new antenna system exhibits a beamwidth of 190° with a peak gain of 6.8 dBi at 3.5 GHz and the beamwidth of 58° with a peak gain of 8.3 dBi at 5.8 GHz. The proposed method is useful for achieving beam diversity in multiband antennas. Simulation results from ANSYS HFSS and experimental measurements of the fabricated prototypes are provided.