M.Sc Thesis


M.Sc StudentSilverstein Daniel
SubjectDesign of Irregular Antenna Arrays Operating in the
Presence of a Structure for Shaped-Beam Radiation
using Reciprocity and Sparse
Optimization
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROFESSOR EMERITUS Yehuda Leviatan
Full Thesis textFull thesis text - English Version


Abstract

Antenna array design and shaped-beam synthesis are used in many applications such as communications, radar, and RF sensors. In order to improve performance while maintaining a small number of elements, sparse optimization was proposed. In most of these studies, the antennas are assumed to be radiating isotropically in free space. However, in practice, the antennas are not isotropic and are often placed near or embedded within a structure whose effect must be accounted for in the design process.


In this study, we extend the design methodology to the case of more realistic antennas radiating in the presence of a structure by considering the current distribution on the antennas and accounting for the antennas’ surroundings. To reduce the complexity of the computational scheme involved in this extension, we resort to reciprocity to allow for an efficient computation of the far-fields of the antennas for many possible placements within or in the vicinity of the structure. Specifically, we do not derive the far-fields of these antennas directly but rather by placing auxiliary dipoles in the far-field of the structure, calculating their fields at all the possible antenna locations, and applying the reciprocity theorem. The reduction in the computational complexity stems from the fact that the incident field upon the structure is spatially smoother and renders the scattering problem from the structure less computationally intensive. Once the far-fields have been computed in this efficient manner, we can proceed and employ any sparse optimizer to design the array.


To demonstrate the proposed methodology, we apply it to various design problems, such as the design of an array of electrically short dipoles in the vicinity of a copper screen, and of an array of electrically short dipoles embedded in a dielectric substrate above a copper plane, with the objective of achieving a single beam in a desired direction. The sparse optimization is shown to yield arrays with more desirable beam patterns (better in terms of least squares error) than achieved by commonly used uniformly spaced planar arrays. The resulting sparse optimization-based array is then simulated with a full-wave solver and results are shown to be in good agreement. The methodology is also demonstrated to be capable of designing antenna arrays with more complex beam pattern requirements, in the presence of a structure.