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Analysis and Design of Wideband Planar 2-D Leaky-Wave Antennas

  • Author(s): Almutawa, Ahmad
  • Advisor(s): Capolino, Filippo
  • et al.
Abstract

Rapid development in wireless communication systems at microwave and millimeter-‎wave frequencies ‎increases the demand for more efficient wideband and high-gain ‎electromagnetic radiator capable of supporting ‎the high-speed data transfer and mitigate ‎the free-space path loss. Fabry-Pérot cavity (FPC) antennas ‎are a potential candidate as ‎radiators ‎since they ‎exhibit useful radiation characteristics, such as high-‎directivity of ‎broadside beam with high radiation efficiency from a low-profile structure, and feature ‎simplicity of ‎design and low-cost fabrication.‎ This two-dimensional (2-D) class of leaky-‎wave antennas (LWAs) are ‎conventionally ‎constructed with a thin frequency selective ‎surface (FSS) (metallic patches or holes in a metallic ‎screen), forming a partially reflected ‎surface (PRS), placed half of a wavelength from a ground plane and ‎excited with a single ‎source.‎

This dissertation focuses on the modal and radiation analysis of FPC antennas formed ‎by an electrically thick PRS ‎‎(single or multiple metal-dielectric layers) optimized for ‎wideband radiation. A novel set of ‎formulas is analytically derived, which relates the ‎leaky-wave parameters (phase and attenuation constants of ‎the traverse complex ‎wavenumber) to the PRS reflection coefficient and input admittance. Additionally, we ‎derived a new leaky-wave based power formula that is capable of describing the far-field ‎behavior for any ‎FPC antenna formed by an arbitrary thick PRS. The formulas are ‎validated with different examples of wideband ‎FPC antennas constructed using single-‎layer and multiple-layers of PRS structures. Moreover, we show how to efficiently radiate ‎‎circularly polarized (CP) waves from a wideband FPC antenna excited by a single ‎CP ‎source. Furthermore, a study was carried out to further enhance the broadside gain with a ‎‎sparse array implemented as a primary excitation source.‎

Additionally, we have investigated the radiation performance of an extremely thin ‎‎(100th of ‎a wavelength) 2-D leaky-wave antenna constructed from a high impedance ‎surface (HIS) directly excited to work as an antenna. Physical ‎insight is provided by ‎analyzing the radiation mechanism of this class of HIS antennas and prove that radiation is ‎‎in part related to a TM-like leaky-wave supported by the structure in the vicinity of its ‎magnetic resonance. ‎Wideband broadside radiation, in addition to a beam steering ‎capability, was demonstrated. Finally, a HIS antenna with a differential feeding network ‎was designed and fabricated for K-band wireless systems.‎

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