Gain enhancement for multiband antenna with frequency selective fractal surface reflector

In this paper, we present a novel frequency selective fractal surface (FSFS) reflector designed for enhancing the gain and performance of a multiband antenna with Hilbert fractal slot in a modified rectangular patch. The composite structure of the antenna includes a wide slot, a Hilbert fractal slot with 1^st iteration, and modified rectangular patch used as additional resonators producing multi-resonant frequencies. The unit cell of FSFS is simple and it consists of the modified fractal geometry. The proposed FSFS is optimized to control the phase and magnitude of reflection and transmission characteristics over a bandwidth suitable for multiband antenna. An effectively in-phase reflection is the key requirement for enhancing of the antenna gains. The results show good multiband operation at the frequency ranges of 880 – 960 MHz, 1710 – 1880 MHz, 1.85 – 1.99 GHz, 1.92 – 2.17 GHz, 2.3 – 2.36 GHZ and 2.4 – 2.485 GHz, respectively. Finally, the designed antenna can operate and cover the applications of GSM, DCS, PCS, UMTS, WiMAX and WLAN IEEE802.il b. Moreover, the antenna gains at the operating frequencies are more than 7 dBi