Analysis of phase variation due to varying patch length in a microstrip reflectarray

The microstrip reflectarray is rapidly becoming an attractive alternative to the more traditional parabolic reflector antenna in some applications. Several variations of the microstrip reflectarray have been designed and fabricated. Amongst the many advantages of the microstrip reflectarray, there are also some serious shortcomings that need to be resolved, particularly the issue of limited bandwidth. The constricted bandwidth is largely attributed to: (i) the narrow bandwidth of the patch elements; (ii) the differential spatial phase delay due to an extended path length between the feed and the reflectarray, and (iii) the phase error related to the changes in patch size. In order to improve the bandwidth of the variable-patch-size reflectarray, the major parameter that governs the bandwidth performance of this class of reflectarray, namely the patch length, must be studied more thoroughly so that its effects on the phase variation can be determined. Such is the objective of the present paper.