Higher-Order Leaky-Mode Bessel-Beam Launcher
Abstract
We present a Bessel-beam launcher based on a leaky radial waveguide consisting of a capacitive sheet over a ground plane that supports higher-order leaky modes. A propagating Bessel beam is generated above the radiating waveguide. The Bessel beam is transverse-magnetic (TM) polarized with a vertical component of electric field that is a zeroth-order Bessel function of the first kind. A higher-order leaky-wave mode is used to reduce losses at millimeter waves and, at the same time, avoid the thin dielectric layers used in previously proposed lower order leakywave Bessel launchers. Closed-form design equations are provided for the proposed structure. In addition, the operating bandwidth of the launcher is defined using dispersion analysis. Near-field measurements of a prototype operating in the frequency range 38- 39.5 GHz validate the concept. The measured launcher generates a Bessel beam with a stable spot size of about 4.3 mm (0.57 λ) over a nondiffractive range of about 16.4 mm (2.2 λ), within about a 4% fractional bandwidth
Keywords
Impedance
high-order modes
higher-order leaky-wave mode
higher-order leaky modes
electromagnetic launchers
frequency 38 GHz to 39.5 GHz
operating bandwidth
electric field
dispersion analysis
Dispersion
capacitive sheet
Bessel beams
Bessel-beam launcher
Bandwidth
artificial surface
leaky waves
millimeter waves
Apertures
millimetre wave propagation
near-field focusing
near-field measurements
leaky radial waveguide
Approximation methods
zeroth-order Bessel function
transverse-magnetic
Prototypes
propagating Bessel beam
Index Terms-Bessel beams
artificial sur- face
Origin : Files produced by the author(s)
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