Wideband hybrid microstrip patch antenna and gain improvement using frequency selective surface

Summary A wideband hybrid microstrip patch antenna with high bandwidth dimension ratio (BDR) is reported in this research work. The electrical dimension of the presented antenna is 0.268λ × 0.201λ × 0.01λ, where λ is the maximum operating wavelength of the antenna. The patch consists of one circle and four parallelograms overlapping with each other. The patch looks like a two dimensional “PINE TREE.” The fabricated antenna exhibits return loss less than −10 dB from 2 to 15.40 GHz with a percentage bandwidth of 154% and BDR of 2859. Also a peak gain of 3.3 dBi is achieved at 8 GHz. To improve the peak gain further over the entire frequency band, proposed antenna is combined with a mono layer stop band frequency selective surface (FSS). Without disturbing the original bandwidth, the antenna is mounted on top of 16 unit cell FSS arranged in of 4 × 4 matrix. When FSS is placed at a suitable minimum distance, maximum gain of 7.22 dBi is achieved by the combined structure. Physical dimension of the proposed FSS combined antenna is 64 × 64 × 35.2 mm, which is very much suitable for long range wireless applications. Both the antenna and the FSS are designed and simulated using Computer Simulation Technology (CST) software. Also it is fabricated on FR4 substrate. It has loss tangent (tan theta) of 0.02, dielectric constant of 4.4, and thickness of 1.6 mm. All the simulation results have been validated using Vector Network Analyzer (VNA). The measured results exhibit good compliance with the simulated results. When FSS is placed at a suitable minimum distance, maximum gain of 7.22 dBi is achieved by the combined structure.