A Compact Printed Unidirectional Broadband Antenna With Parasitic Patch

A printed unidirectional antenna with broad bandwidth and compact size is presented. The antenna is composed of a meandered dipole and a reflector on the top of the substrate. The U-shaped reflector is designed to minimize antenna dimensions as well as to improve the impedance matching and enhance the directivity in lower band. A rectangular metal strip on the bottom of the substrate works as a director for the driven dipole at the upper band. In addition, a parasitic patch is placed between the driven dipole and metal strip to strengthen the coupling between them and therefore dramatically enhances the gain in upper band. Finally, the antenna is fabricated and measured. Experimental results indicate the proposed antenna achieves a broad impedance bandwidth of 67% (2.36-4.74 GHz) and a peak gain of 5.4 dBi. Dimensions of the antenna are 0.41 λ
_g
× 0.42 λ
_g
. It has a minimum front-to-back ratio of 10 dB within the whole band. Due to the compact size, low profile, and broad bandwidth, the antenna is suitable for various directional wireless systems.