A Uniplanar Ultrawideband Antenna With Unidirectional Radiation for WLAN/WiMAX Applications

This letter presents a design of a uniplanar ultrawideband antenna with unidirectional radiation pattern. The antenna design starts from a folded dipole. A modified U-shaped reflector is utilized to introduce a new resonance and improve the front-to-back (F/B) ratio at lower band. A parasitic patch and a director are employed to enhance the performance of the antenna at upper band. Moreover, a higher order mode of the folded dipole is excited to increase the bandwidth further using two strips which are connected to the folded dipole. A prototype is fabricated and measured. The measurements show that the antenna has a bandwidth of 85.1% (2.37-5.88 GHz), a peak gain of 6.9 dBi, and a compact size of 40 mm x 40 mm. In addition, it has the minimum F/B ratio of 10 dB across the whole passband. Due to the advantages of wideband, compact size, planar structure, and easy fabrication, the proposed antenna is suitable for various wireless communication systems.