CHARACTERISTICS OF A HELICAL TAPE ANTENNA EMBEDDED IN A MULTILAYER DIELECTRIC COATED CYLINDER

The dispersion relation and radiation characteristics of a tape helix with two layers of dielectric substrates and one layer of dielectric s uperstrate is derived and analyzed. The derivation is based on the hyb rid mode field expressions in cylindrical coordinates with unknown exp ansion coefficients. The application of the appropriate boundary condi tions and the point matching technique is used to determine the expans ion coefficients. It is assumed that the tape current has only one com ponent along the length of the tape for small values of tape width. Th e dispersion relation is obtained based on an approximate representati on of the current on a narrow tape helix. The k-beta diagram is then o btained from the solution of the complex dispersion relation. The radi ation patterns of the first and second propagating modes, for a finite number of turns of the tape helix, are presented for different geomet rical and electrical parameters.