Gain enhancement of a wide‐slot antenna using dual‐layer, bandstop frequency selective surface as a substrate

A technique for enhancing the gain of a conventional wide‐slot antenna over the wide frequency band using a dual‐layer, low‐profile, bandstop frequency selective surface (FSS) is presented in this article. The dual‐layer FSS exhibits transmission below −10 dB and a linear phase variation with frequency in the range of 4–7 GHz. Unit cell dimension on the order of 0.2λ is used for the FSS layers with respect to the center frequency of operation. The FSS is used as a substrate below the antenna that allows in‐phase reflection of radiated waves leading to enhancement in its gain in the broadside direction over entire operating band. An improvement of upto 3‐dBi gain is achieved over 4–6.5 GHz frequency band with a peak gain of 8.4 dBi. Spacing between the antenna and FSS layers is much less than the conventional quarter wavelength value. Simulation and measurement results are presented in each case.