A High Gain and Compact CPW-fed UWB Antenna Based on a Novel Frequency Selective Surface with Angular Stability

This study presents a compact co-planar waveguide (CPW) ultra-wideband (UWB) antenna integrated with a novel frequency selective surface (FSS) for gain improvement. The novel FSS is created by etching some slots on a square patch and adding different patches during five steps. The presented FSS provides transmission coefficient lower than - 10 dB and reflection coefficient close to 0 dB across the frequency bands of 3-15.7 GHz, and 3.6-15.1 GHz for transverse electric (TE) and transverse magnetic (TM) modes with adequate angular stability, respectively. Angular stability is maintained up to theta = 85 degrees and 40 degrees in the TE and TM planes, respectively. Furthermore, the reflection phase decreases linearly piecewise, making it appropriate for radiation enhancement of the antenna. A 4 x 4 array of the proposed FSS unit cells is positioned below the circular CPW antenna at an optimized distance of 20 mm. Then, to improve the reflection coefficient, a rectangular notch is etching on the radiating patch. The modified structure operates over an impedance bandwidth (S11 < - 10 dB) of 3.4-13.8 GHz for UWB applications with a peak gain of 7.40 dBi at 12.5 GHz. The overall physical and electrical volumes of the proposed antenna are 32 x 32 x 23.2 mm3 and 0.36 lambda(L) x 0.36 lambda(L) x 0.26 lambda(L) (lambda(L) is the wavelength at the lower frequency), respectively that is considerably compact. The proposed antenna is fabricated, and the comparison of the simulated and measured results shows a good agreement.