A Corporate Fed Coplanar Folded Slot Antenna Array and Its Application for Beam Steering Mina A. Iskander 1 , RongLin Li 1 , Dimitris E. Anagnostou 1, 2 1 ECE Department South Dakota School of Mines and Technology Rapid City, SD 57701 USA Email: [email protected] Michael T. Chryssomallis 2 2 ECE Department Democritus Univ. of Thrace Xanthi, 67100, Greece Email: [email protected] Benjamin D. Braaten 3 3 ECE Department North Dakota State University Fargo, ND, 58102 Email: [email protected] Abstract—We demonstrate a corporate fed coplanar folded slot antenna (CFSA) array and its application for beam steering. The design methodology, the return loss and the radiation pattern measurements of the CFSA array are presented. The beam steering of the array can be achieved by using a phased array that is incorporated with three phase shifters. I. INTRODUCTION The coplanar folded slot antenna (CFSA) has the advantage of easy realization. A reconfigurable coplanar folded slot antenna without bias network has been demonstrated in [1]. For a high gain or a phased beam steering application, a CFSA array is needed. A useful technique for a CSFA array is to use a feed, such as those described in [2], [3]. However, a series feed usually leads to a narrow bandwidth and a frequency- dependent radiation pattern, and that is not suitable for a phased array for beam steering. In this paper, we demonstrate a corporate fed CFSA array and its phased array application. II. CORPORATE FED CFSA ARRAY The geometry of a corporate fed coplanar folded slot antenna (CFSA) array is illustrated in Figure 1. The CFSA array consists of four CFSA elements. The design of the individual CFSA element has been described in [1] and [4]. The CFSA has several interesting characteristics. It has more gain and more bandwidth than the dipole antenna, and it is conformal and uni-planar. It can also be made flexible by using thin bendable substrates. The design of the CFSA array was carried out based on an RO4003C substrate with ε r = 3.38. A microstrip corporate network is used to feed the CSFA array. There is a transition between the microstrip line and the CPW feed for each CFSA element. For the transition, the ground planes for the micostrip lines and of the CPW lines are connected by an array of vias. The input impedance of each CFSA element is designed to be 100 Ohms. A 70-Ohm quarter-wave transformer is incorporated in the CPW feeding network to achieve good impedance matching between the 100-Ohm of each CFSA element and the 50-Ohm characteristic impedance of the corporate feed. A prototype of the corporate fed CFSA array is displayed in Fig. 2. The simulated and measured results for the return loss of the CFSA array are plotted in Fig. 3. Results show a resonant frequency around 5 GHz. The simulated and measured radiation patterns at 5.1 GHz are compared in Fig. 4. Good agreement is observed. The antenna gain of the CFSA array is more than 10 dBi at 5.1 GHz. Folded slot antenna Feed network x y z Figure 1. Geometry model of the 4x1 corporate fed CFSA array. Figure 2. Photo of the prototype of the corporate fed 4x1 CFSA array with the SMA connector. The vias of the microstrip to CPW transition can be observed. 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 30 25 20 15 10 5 0 Measured Simulated Return loss (dB) Frequency (GHz) Figure 3. Simulated and measured return loss of the 4x1 CFSA array. A resonance around 5.1 GHz with large bandwidth (approximately 4.8 GHz to 5.4 GHz) is observed. 978-1-4673-0462-7/12/$31.00 ©2012 IEEE