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2 results

  • Characterization and Comparison of Formulas for Optimizing Broadside Radiation and Null Beams in 2D Leaky-Wave Antennas

  • Walter Fuscaldo, David R. Jackson, Alessandro Galli
  • Journal:
    International Journal of Microwave and Wireless Technologies , First View
    Published online by Cambridge University Press:
    27 December 2024, pp. 1-7
    • Article
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  • Two-dimensional (2D) leaky-wave antennas (LWAs) are commonly designed to radiate pencil beams at broadside and/or scanned conical beams. Recently, the possibility to radiate narrow null patterns at broadside has also been preliminarily explored. In this work, we first review the design rules to obtain a pencil beam from an infinite 2D LWA and then show how they change for having a beam with a narrow null at broadside. The effects of antenna truncation are also accounted for in both cases, and numerical results show how the optimum conditions are in turn affected. Finally, full-wave validations of practical structures excited with either horizontal or vertical dipoles validate the analysis.

  • 3 - Semiclassical Treatment of Light Absorption and Scattering from Atoms

  • Chiao-Yao She, Colorado State University, Jonathan S. Friedman
  • Book:
    Atmospheric Lidar Fundamentals
    Published online:
    24 February 2022
    Print publication:
    03 March 2022, pp 17-49

  • Summary

    In Chapter 3, we move to a semiclassical treatment (quantum theory) of light absorption and scattering, specifically from atoms. We start with a description of how lidar measures Doppler shift, and the fundamental difference between the measurement when the laser is in resonance with an atomic transition (resonant) and when it is not (nonresonant). We follow with a treatment of quantum polarizability and the resulting absorption cross section, leading to the differential resonance scattering cross section and its contrast with the classical result. After quantum polarizability, we demonstrate the radiation pattern of coherently excited atoms. This takes us to an interpretation of the Hanle Effect. Following these descriptions of the phenomena that impact resonance lidar, we extend our understanding by closing the chapter with an overview of the rudimentary physics of sodium laser guide stars.