Gain Enhancement of a Wide Slot Antenna Using a Second-Order Bandpass Frequency Selective Surface

Gain enhancement of a wide slot antenna over a wide frequency band using a low profile, second order bandpass frequency selective surface (FSS) as a superstrate is presented in this paper. The proposed multilayered FSS with non-resonant unit cells in each layer allows inphase transmission of waves radiated from the antenna over a 3dB bandwidth of about 50%. The design allows an enhancement of up to 4 dBi in the antenna gain over the entire frequency band (5-8 GHz) of operation. The FSS provides a very low insertion loss between the two transmission poles along with a linearly decreasing transmission phase over the band. The composite structure shows an impedance bandwidth (-10 dB) of 65% with an average gain between 6-8 dBi over the frequency band with a peak gain of 9 dBi. Measurement results of the fabricated prototype matches well with the predicted values.