Electronic Theses and Dissertations

Date of Award

1-1-2024

Document Type

Dissertation

Degree Name

Ph.D. in Engineering Science

First Advisor

Alexander B. Yakovlev

Second Advisor

Ramanarayanan Viswanathan

Third Advisor

Lei Cao

Relational Format

dissertation/thesis

Abstract

It is a well-known fact that antennas form the very core of the modern wireless communication systems. As such, an escalating demand for increase in the wireless system capacity compels and necessitates accommodation of densely packed antennas in a very compact space. However, a practical design of such dense antenna systems may not only be cumbersome but could also lead to the deterioration of the overall system performance, considering the fact that such a system may suffer from destructive interference, owing to the cross-coupling between the antenna elements jammed together. In this regard, we endeavor to curb the detrimental effects of mutual coupling by exploiting the concept of electromagnetic invisibility, essentially by employing the mantle cloaking technique, which is based on the concept of scattering cancellation. For this purpose, we have designed specialized covers, called metasurface cloaks, to facilitate the decoupling and cloaking phenomena in different printed and slotted antennas as well as their interleaved array scenarios. We have demonstrated through numerous simulation results that, by incorporating each antenna element with suitably designed metasurfaces, the tightly spaced antennas and, by extension, antenna arrays are decoupled in the near field. Additionally, their radiation properties are also restored in the far-field, as if each antenna was functioning in an isolated fashion. Consequently, the interleaved antenna arrays do not sense the presence of each other, which enables them to radiate unhindered for various beam-scanning angles. In this dissertation, we have exemplified the decoupling and cloaking effects of the corresponding metasurface cloaks for closely spaced printed monopole antennas, slot antennas, rectangular, triangular and circular microstrip patch antennas, along with their interleaved array configurations, at microwave frequencies. Furthermore, at low terahertz (THz) frequencies, cloaking of different cylindrical objects (circular and elliptical) as well as a 2D perfect electric conductor (PEC) strip (which is modeled as a degenerated ellipse) using graphene-based metasurfaces, is also presented.

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