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Low Profile Corrugated Structures for Surface Wave Suppression and Multipath Mitigation in GNSS Antennas

  • Author / Creator
    Taghdisi, Ehsan
  • Multipath interference is an error generating issue in high-accuracy global navigation satellite system (GNSS) applications. Since the propagation of surface waves along the surface of antenna structure is the root cause for reception of multipath signals in GNSS antennas, surface wave suppressing ground structures are needed for GNSS antennas that are employed in high-precision GNSS applications. Two-dimensional (2D) corrugated structures, also known as choke rings, are commonly used as the ground structure for high-accuracy GNSS antennas. Despite their superior performance, choke rings suffer from large size, heaviness, costly fabrication, and inability to integrate with printed circuit board (PCB) structures. The objective of this thesis has been to design low-profile substitutions for these bulky structures.
    First, a review of literature is conducted on the multipath signals, surface waves, and surface wave suppressing ground structures to acquire a deep understanding of the problem and techniques to analyze it.
    Then, a compact dual-band substrate integrated choke ring (SICR) ground structure has been designed by engineering the location of via holes and partial copper cladding of the substrates in a multilayer structure.
    Next, a novel technique for miniaturization of corrugated structures is presented and folded corrugations are introduced. The miniaturization is achieved by implementing a fold or slit inside each corrugation. The proposed miniaturization technique is modeled using the modal expansion method and an equivalent circuit is extracted which precisely models the surface impedance of the proposed folded corrugation. A time-efficient deign procedure is presented based on the equivalent circuit model and a Folded SICR (FSICR) structure is designed.
    Finally, the idea of folded corrugations is expanded to multi-folded corrugations (MFCs) to achieve further miniaturization. The design procedure is adjusted as well to design dual-band multi-folded corrugated structures. A dual-band Double-Folded SICR (DFSICR) structure is designed to suppress the propagation of surface waves over the main GNSS frequency bands, L1 (1573-1587 MHz) and L2 (1215-1240 MHz).
    The performance of the proposed structures has been investigated by mounting a right-handed circularly polarized (RHCP) GNSS antenna on it. The introduced designs demonstrate significant multipath mitigation capabilities, close to that of a classic choke ring, while they eliminate the drawbacks of a conventional one.
    An example design of DFSICR shows miniaturization of 85% in height and 38% in diameter compared to the conventional choke rings. It also demonstrates weight reduction of more than 90%, thanks to its substrate integrated design.
    It worth noting that although the motivation behind the introduced miniaturization technique has been to address a problem in GNSS antennas, the approach looks promising for miniaturization of other corrugated structures such as spoof surface plasmon polariton (SPP) waveguides and components.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • 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.