Linear Array of a Probe-Fed Elliptical Ring Antenna Krittaya Nakprasit , Chuwong Phongcharoenpanich* , Sompol Kosulvit and Monai Krairiksh Faculty of Engineering and Research Center for Communications and Information Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520 Thailand, E-mail: kpchuwon@kmitl.ac.th Introduction It is well known that cellular mobile system plays a role for life utility [1]. Therefore, the investigations of the mobile antenna at the base station are significant. Generally, the omnidirectional antenna is employed for circle area. However, it is obvious that a bidirectional antenna that has suitable characteristics is desired for long- and narrow-area application such as the highway, the tunnel, and the corridor. Since the demand on cell is very large, cost effective must be considered. The authors have proposed a bidirectional antenna array using a probe excited circular and rectangular rings [2]-[3]. However, the antenna characteristics primarily depend on the ring dimensions. The cross section of the ring can be designed to achieve the dominant mode propagation. The elliptical ring has an advantage that the antenna characteristics can be chosen by varying the semi-major and semi-minor axes. The array configuration is used for improving the radiation characteristics of an element. An element of a probe-fed elliptical ring antenna The structure of a probe-fed elliptical ring antenna radiating bidirectional pattern consists of a linear electric probe of length l aligned along y axis, and this probe is surrounded by an elliptical ring of the semi-major axis a and semi-minor axis b. At the two ends of the ring, there are two elliptical apertures on the planes z = - d/2 and z = d/2 , respectively, as shown in Fig. 1. Figure 1. A probe-fed elliptical ring antenna In order to obtain the dominant mode propagation at the desired operating frequency [4], the antenna dimension is designed in term of wavelength as tabulated in Table 1. Radiation characteristics of an element As depicted in Fig. 2, a probe-fed elliptical ring antenna of the parameters in Table 1 can provide directivity of 7.07 dBi with the HPBW in E-plane ( 9 and H-plane of 83 and 46 degrees, respectively. There is no side lobe in the radiation pattern for single element of a probe- fed elliptical ring antenna. 0 o φ = ) ) ( 0 o φ = 0-7803-8883-6/05/$20.00 ©2005 IEEE