Development of full wave Green's functions for expeditious method of moments analysis of spiral antennas embedded in multi-layered dielectric cylinders

• Main Author: Wu, Jun
• Published: University of Sheffield 2011
• Subjects: 621.3824
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555241

Spiral antennas have a wide range of applications in communications because they are circularly polarized with broadband characteristics with respect to both input impedance and radiation pattern. However, a spiral antenna that is conformal to a multilayered cylindrical media has not been reported in earlier studies. This thesis presents in depth analysis of such antennas using a full wave Method of Moments model. There are two crucial issues involved in such model: developing efficient spatial domain Green's function expressions, and then linking the Green's functions with the Method of Moments. An efficient algorithm to compute Dyadic Green's functions in stratified cylindrical media has been developed firstly. The convergences of the Green's functions have been greatly accelerated by employing a single asymptotic extraction in the spectral domain and the counterparts of those subtracted components in the spatial domain have been derived into compact closed-forms. On the other hand, two different methods to link the Green's functions and Method of Moments have been developed: look-up-tables and segment based approach. The look-up-table approach is efficient for modeling conformal antennas, while the segment based approach is especially suitable to model conformal antennas with a probe feed. The whole method has been validated by comparing computed results with those from CST or equivalent planar geometries. As a result, an efficient method to model antennas conformal to stratified cylindrical media incorporation with Method of Moments has been developed.