Contoured-Beam Reflectarray Antenna for Indoor WLAN Access Points

In the wireless communication applications such as the large-scale indoor base station of wireless local area network (WLAN) system, it is desirable for antenna beam to cover a broad area. At present, the popular antennas for indoor WLAN access points are linear dipole, slot array, and microstrip antenna. These antennas will be usually placed at the wall of rooms or buildings. However, most kinds of these antennas have omnidirectional pattern. Therefore, they are not suitable for field radiating in the large room because of power loss in unnecessary directions such as outside of room. This argues if we can design an antenna to illuminate a predefined complex coverage area without substantial spatial variation, it will have more efficient for field radiating. Thus for solve a problem aforementioned, the widely shaped beam antenna is an alternative for WLAN applications as shown in Fig.1 [1]. This antenna will use installation area the ceiling. The associated literatures have been reported by several authors. Smulders et al. [2] presented the design of a 60 GHz shaped reflector antenna for WLAN access points by using backscatter reflector, which fabricated from the modified parabolic surface. Also, Wongsan and Thaivirot [3] presented the synthesis of radiation patterns of the variety of shaped backscatters to provide the wide beam for indoor WLAN applications. From [2]-[3], the backscatters have been fabricated from the circular metal sheet that their surfaces are shaped to be geometric curvature. In case of WLAN systems, such antennas are improper because their structures suffer from mechanical drawbacks such as bulkiness and the need for an expansive custom mold for each coverage specification.