Antenna-Filter-Antenna-Based Structures in Transmit-Arrays and Frequency Selective Surfaces

  • Author / Creator
    Naseri, Parinaz
  • Transmit-array (TA) antennas have shown to be a low-cost, low-profile, and viable solution for point-to-point communication such as in satellite application. The existing work on TA and its unit-cell suffers from various drawbacks including fabrication difficulties and unnecessary losses. The focus of this work is on circularly-polarized (CP) TAs and its goal is to propose a unit-cell with better performance and increased number of supported frequency bands. The proposed unit cells are antenna-filter-antenna (AFA) elements composing of a receive antenna, a non-radiating resonant structure, and a transmit-antenna operating between the input and output radiating ports. The AFA elements can be configured in non-uniform arrays to implement TA antennas or alternatively configured in uniform arrays to implement Frequency Selective Surfaces (FSS). The AFA can be considered as a spatial filter that can adequately change the amplitude and phase of the incident wave passing through it, whereby both arrays, e.g. FSS and TA, can shape the polarization and/or directivity of the antenna illuminating them. The introduction chapter discusses the existing solutions as TA unit-cells, employed methods, and their shortcomings. The Chapter two talks about single-band CP TA antenna. We propose a novel unit-cell, besides those currently presented in the literature, to achieve high-gain CP steerable radiation pattern. The required phase shift of a TA is achieved by rotation of its unit-cells. To do so, the incident wave to the TA has to be CP and its sense has to change after passing through the TA. Therefore, the unit-cell is structured in two different TA configurations with different phase distribution across these TAs. The first TA is to diverge the feed’s radiation to broadside and the latter one is to concentrate and redirect the source’s radiation to -15˚-off broadside. Therefore, the TAs were put in front of a conventional 2×2 array of sequentially rotated CP patches with gain of 12 dB at f=20.5 iii GHz. The maximum gain of the first TA is 22dB at broadside and the maximum gain of the second TA is 21.5dB at -15˚-off broadside. In Chapter 3 we introduce a novel dual-band CP TA unit-cell which manipulates the two orthogonal linear components of a CP wave in a way that they exit with equal magnitude and 180˚ phase difference. Therefore, the polarization of the illuminating wave will change and its phase can be controlled by rotation of the unit-cell. To the best of our knowledge, this unit-cell is the first TA element operating at two different frequency bands with insertion loss better than 1 dB at both and providing continuous 360˚ phase shift in the transmitted wave. This element can be also employed in a uniform array of FSS. Therefore, the FSS will work as a polarization converter at two frequency bands. This application can be useful in GPS navigation system in which having the same polarization on the two sides of a bidirectional CP antenna is important

  • Subjects / Keywords
  • Graduation date
    Spring 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.