Planar microstrip reflectarray have been proposed as a replacement for conventional parabolic reflector antennas because of their compactness, lightweight, and low manufacturing cost, To focus an incoming plane wave onto a receiver, the planar microstrip reflectarray employs a large array of phase shifting elements, often more than several thousands, Each of the elements has a different reflected phase to compensate for the phase difference due to the different path length from the receiver to the array element. There are several schemes to provide the phase compensation. One approach is to use identical microstrip patches with delay line of different length attached to the patch [1-3]. The second approach is to use different sizes of patches only [4]. Another approach is Its use variable rotation angles of patches with stubs [5] for circular polarization applications. In these papers, the numerical analysis ignored the coupling among the microstrip elements. In contrast, [6] takes into account the entire coupling among the elements leading to a very extensive computation in terms of both computer memory requirement and CPU time. In this paper, we present a quantitative analysis of the coupling effect among the reflectarray elements that takes into consideration sufficient coupling effects without substantially increasing the computation time. In addition, a special arrangement of elements in the reflectarray is found to reduce the first side lobe of the radiation pattern.
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