Reduction of Mutual Coupling between Two Dielectric Resonator Antennas Mounted on a Circular Cylindrical Ground Plane. S. H. Zainud-Deen, H. A. Malhat, and K. H. Awadalla Faculty of Electronic Engineering, Menoufia University, Egypt. E.mail: anssaber@yahoo.com, er_honida@yahoo.com Abstract: In this paper, the radiation characteristics of two-element array of DRAs mounted on the surface of a hollow circular cylindrical ground plane are explained. The finite element method and the finite integration technique are used to calculate the radiation characteristics as well as the mutual coupling between the array elements. Mutual coupling reduction is obtained by cutting slots, or inserting quarter wavelength grooves in the surface of the cylindrical ground plane between the antenna elements. I. Introduction: Dielectric resonator antennas (DRAs) are attractive as electromagnetic wave radiators due to high radiation efficiency, ease of excitation, simple geometry, compactness and ability to obtain different radiation characteristics using different modes of operation [1]. The advantages of DRAs make them as practical elements for antenna applications at microwave frequencies [2, 3]. Antennas on cylindrical structures play considerable roles in modern communication systems. Mutual coupling or isolation is a term that describes the electromagnetic wave interaction between antenna elements placed in close proximity [4]. This interaction causes some consequences on the antennas’ characteristics including distortion of the radiation pattern, input impedance, gain and efficiency. A notable class of electromagnetic bandgap (EBG) structures named defected ground structure (DGS) is recently introduced and has controllable finite transmission zero characteristic [5, 6]. Thus mutual coupling reduction is achieved. Through out this paper, the mutual coupling between two-element DRAs array mounted on a cylindrical surface and their radiation characteristics are computed using the finite element method and the finite integration technique [7, 8]. The mutual coupling is reduced by cutting slots, or inserting grooves in the surface of the cylindrical ground plane between the antenna elements. II. Numerical Structure The construction of two identical CDRA over a hollow circular cylindrical ground plane is shown in Fig.1. The CDRA has dielectric constant (ε r ) 12 radius, “a” of 4.2 mm and a height, “b” of 3 mm. A coaxial probe with radius of 0.2 mm excites the antenna and located off the center by d f = 3.5 mm with a height, “h” of 2.4 mm. The CDRA is designed to operate around 10 GHz. However, the resonant frequency is altered due to ground plane curvature. The length of the circular cylinder, “L” is 100 mm with thickness 0.6 mm. Fig.2 shows the magnitude of the mutual coupling coefficient, S 21 , as function of separation, in wavelength, between the two CDRAs for both E – plane coupling and H – plane coupling at f=9.5 GHz when cylinder radius R=15, 50, and 100 mm. The figure includes the results for E-plane coupling and H-plane coupling for planer infinite ground plane from [9]. Fig. 3 shows the radiation patterns for the coupled antennas, CDRAs, in different orientations using the same input voltage excitations with R= 15 mm at f= 9.5 GHz. Two identical CDRA mounted on a hollow circular cylindrical shape with defected ground plane structure (DGS) is presented in Fig.4. The DGS is composed of cutting slots in the cylinder surface (case 1). The axis of the slot is perpendicular to the cylinder axis. The slot radial length L s , width W s , depth H s , and the slots separation d s . The dimensions of the slot are designed for their stop-band around 9.5 GHz. The mutual coupling coefficient S 21 between two identical CDRAs (with dimensions as in Fig.1) versus frequency for one slot, two slots and three slots is shown in