Fast electromagnetic analysis of large objects involving planar layered media : application to antenna arrays and metasurfaces
(2021)
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- Authors
- Supervisors
- Craeye, Christophe
- Abstract
- The constant evolution of wireless technologies has favoured the development of antenna systems. The increasingly restrictive market requirements are pushing towards the development of larger and more complex antenna arrays. This trend calls for fast design procedures which require the efficient and accurate characterization of antennas. Although analytical thinking allows the determination of initial rules of thumb, recent and future designs are almost impossible to analytically characterize and a crucial role is played by computational electromagnetics (CEM). CEM combines innovative numerical methods and computational resources to enable the fast validation of new designs and their optimization under the constraints imposed by the designated applications. Although CEM has come a long way since its creation, many advanced numerical methods have been developed under simplifying hypotheses such as the regularity of antenna arrays, the infinite ground plane assumption, canonical shapes of (parts of) the antennas, or ideal representations of the feeding structures. While these hypotheses lead to efficient numerical methods, they represent a setback when confronted to the constraints encountered in industry. This is why this thesis aims to contribute to the advance in CEM by developing numerical methods capable of effectively simulating electrically large arbitrarily-shaped structures while accounting for practical constraints that have been often neglected before. Doing so, numerical techniques are developed for two classes of problems involving layered media. The first class concerns the simulation of large irregular antenna arrays on a finite ground plane and the second class concerns the simulation of arbitrarily-shaped metasurface antennas. The first part of this thesis is directed towards the analysis of large irregular antenna arrays on a finite ground plane devoted but not limited to radio astronomy applications. The resolution of new radio telescopes targeting unprecedented dynamic range can be altered if effects such as scattering by finite ground planes are not properly included. In this framework, an advanced Method of Moments (MoM) based technique is presented to simulate arrays on a finite ground plane itself lying on a layered medium. In particular, the research leads to a new formulation of the electric field radiated by the antenna on the ground plane, expressed as a finite series of Hankel functions and associated Anger-Weber functions. This new formulation allows the fast evaluation of the interactions between the antennas and the finite ground plane. The second part of this thesis is devoted to the fast simulation of large arbitrarily-shaped metasurface (MTS) antennas. MTS antennas are usually realized as a subwavelength arrangement of printed patches on a grounded dielectric layer. This metallic grid creates periodically modulated boundary conditions that couples with the surface wave launched by the feeder, which allows the structure to radiate by leaky waves. MTS antennas are currently receiving considerable interest owing to the fact that they represent a promising technology. Modulated MTS antennas represent a low cost, low-profile and easy-to-feed class of antennas. They form a promising alternative to phased array technology which, in spite of its tremendous capabilities, represents a bulky and high-consumption approach. Nowadays, efficient methods for the simulation of MTS antennas exist. However, these methods are restrained to MTS with a canonical shape (e.g. circular, elliptical, etc) and usually use a vertical elementary dipole to feed the antenna. In this thesis, an efficient FFT-based method is developed to simulate arbitrarily-shaped, possibly cascaded MTS antennas. This method is then combined with models representing the fine geometry of the feeder which allows the numerical evaluation of the MTS input impedance. Finally, an optimization algorithm based on this technique is presented to maximize the efficiency of MTS antennas.
- Affiliations
Citations
Cavillot, J. (2021). Fast electromagnetic analysis of large objects involving planar layered media : application to antenna arrays and metasurfaces. https://hdl.handle.net/2078.5/110776