Modelling of ultra-wide stop-band frequency-selective surface to enhance the gain of a UWB antenna

Here, an ultra-wide stop-band single-layer frequency-selective surface (FSS) with high-incidence angle independence has been proposed to enhance the gain of an ultra-wideband (UWB) monopole antenna. The unit cell (0.2 lambda x 0.2 lambda) of the proposed FSS consists of four asymmetric rectangular patches with circular slots embedded in it. This concept of four slotted patches is conceived to achieve ultra-wide stop-band characteristic over 4.7-14.9 GHz. An equivalent lumped circuit model for the FSS is proposed to provide insight into the working nature of the FSS. A UWB monopole antenna is also designed and integrated with the proposed FSS. Ultra-wide stop-band single-layer FSS converts the omnidirectional pattern of the monopole antenna into a unidirectional one and thereby registers a significant increase in its gain by 4.5 dBi. The design concept has been discussed and experimentally verified using simulated and measured results.