Polarization-handedness-dependent Omnidirectional Conical Leaky Wave Radiation

Research output: Contribution to conference (unpublished)Abstract

Authors

  • Yahong Liu
  • Kun Song
  • Qinghua Guo
  • Xiaopeng Zhao

Colleges, School and Institutes

External organisations

  • Northwestern Polytechnical University
  • International Collaborative Laboratory of 2D Materials for Optoelectronic Science and Technology of Ministry of Education, Shenzhen University

Abstract

Reconfigurability and tunability are a desirable feature to reduce the number of components in engineering systems. Lumped elements (e.g., PIN diodes, varactor diodes, RF_MEMS), tunable materials (e.g., liquid crystal, ferroelectric thin film, photo-conductive), and mechanical approaches are the standard strategies in agile microwave technology [1]. It is surprising thought that microwave engineers have not exploited more comprehensively polarization as a mean for reconfigurability/tunability since it is a standard strategy in optical technology.
Inspired by the recent studies related to spin-orbit coupling of light in the physics community [3], we explore the use of polarization to tune the omnidirectional conical leaky wave radiation of a short-circuited helical tape from forward to backward. When the incident circularly-polarized wave is of opposite handedness as the helix, forward omnidirectional conical radiation is achieved, akin to a helical antenna operating on a higher-order mode (rather than on the normal or axial/beam mode) [4]. When the incident circularly-polarized wave is of the same handedness as the helix, the signal travels along the helical tape with no radiation until it is reflected by the end mirror; then, the handedness of the reflected signal coincides with the helix and backward (for the original coordinate system) omnidirectional radiation is achieved. The underlying mechanism is explained in terms of Floquet theorem.
Two helical tape waveguides of length 430 mm (~13λ0) operating within the X band are fabricated using a circular resin pipe wrapped with copper foil. Prototype 1 is a uniform helix tape while prototype 2 has a Taylor amplitude taper [1] to reduce side lobe levels. The S11 of both prototypes is below -10 dB regardless of the polarization from the cutoff frequency of ~8.4 GHz up to ~9.6 GHz where the second space harmonic enters the radiation region. Prototype 1 shows a realized gain of ~10 dB with -15 dB side lobe levels. Prototype 2 shows a realized gain of ~13 dB and -20 dB side lobe levels. Numerical (using CST Microwave Studio®) and experimental results are in good agreement.

[1] J. L. Hilbert, Tunable RF Components and Circuits: Applications in Mobile Handsets (Devices, Circuits, and Systems), CRC Press, 2015
[2] Y. Liu, Q. Guo, H. Liu, C. Liu, K. Song, B. Yang, Q. Hou, X. Zhao, S. Zhang, and M. Navarro-Cía, Circular-Polarization-Selective Transmission Induced by Spin-Orbit Coupling in a Helical Tape Waveguide, Phys. Rev. Appl. 9, 054033 (2018).
[3] J. D. Kraus and J. C. Williamson, Characteristics of helical antennas radiating in the axial mode, J. Appl. Phys. 19, 87 (1948).

Details

Original languageEnglish
Publication statusPublished - Feb 2019
EventIET Colloquium on Antennas and Propagation for 5G and Beyond - IET Birmingham: Austin Court, Birmingham, United Kingdom
Duration: 28 Feb 2019 → …

Conference

ConferenceIET Colloquium on Antennas and Propagation for 5G and Beyond
CountryUnited Kingdom
CityBirmingham
Period28/02/19 → …