Summary
International Symposium on Antennas and Propagation
2010
Session Number:2WA2
Session:
Number:2WA2-3
Dual Layer Minkowski Radiating Shape for Reflectarray Antenna Design
A. Wahid, M.K.A. Rahim, F. Zubir, S.H.S Ariffin, S.K.S Yusof,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
The reflectarray combine the best features of both reflector and an array in that better performance especially in antenna gain which can be achieved without using complex and lossy corporate transmission line feed network. A reflectarray have many advantages that can be categorized into two points of view which are from electromagnetically and mechanically. From an electromagnetically perspective, they are high gain antennas, low side lobes, capable of beam steering, and from a mechanically perspective, they have lightweight structures, easy to fabricate and manufacture and also robust [1]. In contrast, the narrow band of the radiating elements and the non-constant path delay between reflectarray elements are the two major factors that causing a reflectarray antenna has narrow bandwidth [2]. The original reflectarray designed on single layer substrate was based on microstrip patches [3]. The problem using microstrip patches is that the microstrip patch is an inherently narrow band radiating element and several concepts has been attempted to overcome this setback for reflectarrays based on various configurations [4]. It has been shown that the DRA has a larger impedance bandwidth and higher radiating efficiency that microstrip patch antenna [5] and thus is a possible alternative. On the other hand, one of the setbacks of a single layer reflectarray is that the range of reflection phase curve doesn’t reached 360°. It has to have wider phase range as phase compensation in patch variation should be at least 360° [6] and better gradient (°/μm) especially around its resonance region as well as phase linearity. The choice of a double layer variable size element structure offers a smooth reflection phase curves over a range of up to 500° [7], the range unattainable with a single patch layer. Fig. 1 show the illuminating feed of the reflectarray. In this work, a double layer microstrip element in the form of the first iteration of fractals, this is minkowski geometries and square patch are proposed to improve the bandwidth of a microstrip reflectarray. By adjusting the shape of the original square patch into a minkowski shape, a much wider reflection phase range compared to the conventional double layer reflectarray elements is achieved. These new double layer minkowski reflectarray elements are designed within X-band frequency range from 8.4 to 12.6 GHz in CST Microwave Studio. It has been specified to operate at frequency of 11 GHz.