Modal-expansion analysis of monopole antennas coated by a finite-height tensor impedance surface

This paper presents a rigorous analysis of the input impedance of a monopole antenna surrounded by a finite-height tensor impedance surface coating using the modal-expansion method. The tensor impedance surface is approximated by a thin anisotropic slab for facilitating the analysis. In addition, practical coaxial feedline was considered in the modeling. Based on the field expressions for all the sub-regions of the entire structure, the expansion coefficients can be determined by enforcing the tangential field continuity conditions across the boundaries in between adjacent sub-regions. The results calculated by the proposed approach are in a strong agreement with those obtained from commercial full-wave simulators. The proposed method provides a much faster solution and consumes less memory, making it highly useful for further exploration and optimization synthesis of integrated tensor impedance surface coated monopole antennas for a variety of applications.