# Analysis of Conformal Antennas and Periodic Structures

[Doktorsavhandling]

In the last decades much attention has been paid to the design of high-performance antennas. Accurate control of the radiation properties is very important in electromagnetic engineering applications. To this end there is a need to develop numerical techniques able to predict in detail the radiation and scattering performance of microwave antennas on planar and curved surfaces.

This thesis deals with the analysis of planar and circular cylindrical multilayer structures such as loaded dielectric slabs, corrugated surfaces, frequency selective surfaces and microstrip patches for conformal arrays. The thesis consists of fifteen papers: two published journal articles, ten conference papers, two submitted journal articles and a technical report.

Soft surfaces exhibit polarization independent boundary conditions. Because of this property, they can be used in the design of high-performance antennas to minimize undesired radiation effects and to reduce scattering from supporting structures of antennas. Two different applications of soft surfaces are investigated numerically. The Finite Difference Time Domain (FDTD) method is applied for the analysis of the scattering properties of a monopole antenna on a circular, dielectric-loaded ground plane and the Method of Moments (MoM) is used to investigate and optimize a dual-frequency (S/X-band) corrugated horn.

Arrays of periodically spaced conducting elements are often used as filters for microwave applications and are referred to as Frequency Selective Surfaces(FSSs). We have developed algorithms and software for studying the scattering from singly and double periodic surfaces placed either in free space or above a multilayer structure. Both planar and circular cylindrical structures are treated. A spectral domain technique together with the method of moments is used for the analysis.

Microstrip antennas are often used in conformal arrays because of their ability to conform to non-planar structures. Algorithms and software have been developed for analyzing different configurations of rectangular microstrip patch antenna arrays, placed on a multilayer circular cylinder. The methods are based on a spectral domain approach and the method of moments. Input impedance, mutual coupling and radiation patterns are calculated and results are validated against measurements on an experimental model.

**Nyckelord: **conformal antenna, horn, corrugated surface, dual-frequency, periodic, array, infinite, Floquet, method of moments, finite difference time domain, microstrip, multilayer structure, spectral domain analysis

Denna post skapades 2006-08-28. Senast ändrad 2013-09-25.

CPL Pubid: 730