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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Conformal Leaky-Wave Antenna Based on Partially Filled Rectangular Waveguide
摘要： The present paper is devoted to the development of a conformal leaky-wave antenna based on a curved rectangular waveguide. The process of obtaining the required beam position is about longitudinal tailoring the phase velocity. This is achieved with choosing the thickness of dielectric, which partially fills the slotted waveguide. The difference between wavelengths in curved and straight waveguides is taken into account. An amplitude distribution function is realized by means of traditional adjusting the each particular slot parameters. The results of computer simulation validate the proposed design technique.
关键词： rectangular waveguide,dielectric filling,phase velocity,conformal antenna,leaky-wave antenna,beam forming
更新于2025-09-23 15:21:01
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Dephasingless Laser Wakefield Acceleration
摘要： Laser wakefield accelerators (LWFAs) produce extremely high gradients enabling compact accelerators and radiation sources but face design limitations, such as dephasing, occurring when trapped electrons outrun the accelerating phase of the wakefield. Here we combine spherical aberration with a novel cylindrically symmetric echelon optic to spatiotemporally structure an ultrashort, high-intensity laser pulse that can overcome dephasing by propagating at any velocity over any distance. The ponderomotive force of the spatiotemporally shaped pulse can drive a wakefield with a phase velocity equal to the speed of light in vacuum, preventing trapped electrons from outrunning the wake. Simulations in the linear regime and scaling laws in the bubble regime illustrate that this dephasingless LWFA can accelerate electrons to high energies in much shorter distances than a traditional LWFA—a single 4.5 m stage can accelerate electrons to TeV energies without the need for guiding structures.
关键词： ponderomotive force,phase velocity,Laser wakefield accelerators,spatiotemporal pulse shaping,dephasing
更新于2025-09-23 15:21:01
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Spatial waveguide mode separation for acoustic waves in a meta-slab composed of subunits with graded thicknesses
摘要： A meta-slab composed of subunits with graded thicknesses is proposed for spatially separating the zeroth- and first-order acoustic waveguide modes according to the generalized Snell’s law. The phase velocity for the first-order mode depends on the waveguide thickness, whereas that for the zeroth-order mode does not. This enables the required phase-shift gradients of the meta-slab to be obtained for spatially separating the two waveguide modes. To design the meta-slab, analytic solutions are derived for the transmission coefficients and phase shifts of the incident acoustic waves with the two modes propagating through the subunits. Numerical simulations with transient finite-element analyses are implemented to demonstrate the propagation of the two waveguide modes. Sinusoidal signal and tone-burst excitations are applied in the analyses. The latter case shows that the two waveguide modes can be successfully separated in space by the designed meta-slab.
关键词： phase velocity,finite-element analyses,acoustic waveguide modes,meta-slab,transmission coefficients,phase shifts,generalized Snell’s law
更新于2025-09-23 15:19:57