THE RECTANGULAR PATCH MICROSTRIP RADIATOR-SOLUTION BY SINGULARITY ADAPTED MOMENT METHOD

Rectangular microstrip patches are the most widely used radiators in printed antenna arrays. The numerical solutions based on the moment-method techniques provide reliable results for these radiators, but they need a vast amount of computations. This is because the current distribution on the patch has singularities at the feed point and at the edges, and thus a large number of basic functions are needed in the moment expansion of the current. This chapter presents detailed solution of the rectangular microstrip patch that incorporates such singularity functions. The solution includes several stages. First, it describes the Fourier domain presentation of the currents and the fields in the microstrip radiator. Second, the vertical current of the feed is then treated by an equivalence principle, which transforms vertical currents into equivalent horizontal surface currents. The third stage is a moment-method solution of a simplified rectangular radiator whose substrate is air and whose feed is a vertical thin sheet of current mounted across the patch. In the rectangular radiator discussed in the chapter, four types of basic functions are used in the expansion of the current on the radiator: (a) an attachment mode, which describes the singularity at the feed point;(b) an edge mode, which describes the singularity of the longitudinal current derivative at the patch edges; (c) a sum of harmonic functions; and (d) a vertical feed current, which is also included by the equivalence principle mentioned earlier. © 1991 Academic Press, Inc.