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 θ = 85° and 40° 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 × 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 × 32 × 23.2 mm³ and 0.36λ_L × 0.36λ_L × 0.26λ_L (λ_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.