Holographic Surface Leaky-Wave Lenses With Circularly-Polarized Focused Near-Fields—Part II: Experiments and Description of Frequency Steering of Focal Length

The paper discusses the possibility of generating a pseudo-Bessel beam, with a propagation distance of several hundreds of wavelengths in microwave and millimeter frequency band, by using a radial line slot array (RLSA). A specific application for non-contact microwave detection of buried mines has been considered as test case. The design benefits of a holographic approach to assure the required aperture field distribution and makes use of an ad hoc optimization tool to control the antenna slot layout. The predicted and measured antenna behaviors show that high efficiency and polarization purity can be obtained by such a compact and flat antenna, achieving at the same time both manufacturing and setup simplicity.

Section: B Prototypementioning

confidence: 99%

Large Depth of Field Pseudo-Bessel Beam Generation With a RLSA Antenna

Mazzinghi

Balma²,

Devona³

et al. 2014

“…Although some discrepancies are observed between both results, as a result of manufacturing problems with the gap left for the inner conductor of the coaxial probe, the key point is that a good input matching (S 11 < −15 dB) is obtained at the design frequency of 15 GHz and over a band of ∼ 0.5 GHz. It should also be highlighted that this type of leaky-wave lenses are strongly dispersive with frequency as demonstrated in [36], [40]. As a consequence, the designed focal length, F , is only kept for the design frequency, increasing its position for higher frequencies until it eventually breaks into a conical shaped focused spot, as shown in [40].…”

Section: Measured Resultsmentioning

confidence: 98%

“…It should also be highlighted that this type of leaky-wave lenses are strongly dispersive with frequency as demonstrated in [36], [40]. As a consequence, the designed focal length, F , is only kept for the design frequency, increasing its position for higher frequencies until it eventually breaks into a conical shaped focused spot, as shown in [40]. …”

Section: Measured Resultsmentioning

confidence: 98%

“…Two main approaches have been reported in the literature: i) to conform the radiating element so that all sections point to the same focal region as proposed in [37], and ii) to taper the radiated fields by changing the electrical properties along the device and thus avoiding to curve it [35]. Based on this second approach, there have been proposed several technologies and topologies such as focusing plates that require of an external source [38], focusing systems inside parallel-plate waveguides [29], or more integrated devices as in [39], [40]. Other possible designs have been conceived from tapered far-field radiations patterns that make use of a quadratic phase taper to approximate the radiated near-field pattern [41], or by using Bessel beams [42], [43].…”

Section: Design Of the Radial Array Lensmentioning

confidence: 99%

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Non-Uniform Sinusoidally Modulated Half-Mode Leaky-Wave Lines for Near-Field Focusing Pattern Synthesis

Martín

Gómez‐Tornero

Losada

et al. 2015

A novel non-uniform sinusoidally modulated halfmode microstrip structure with application to near-field focused leaky-wave radiation in the backward Fresnel zone is proposed. First, it is presented a dispersion analysis of the constituent backward leaky wave in the sinusoidally modulated unit cell in half-width microstrip technology. This information is then used to design a finite non-uniform line that focuses the radiated fields at the desired point. Finally, eight similar line sources are arranged in a radial array to generate a three-dimensional focused spot located at the desired focal length over the simple central coaxial feeding. Simulated and experimental results are presented to validate the proposed simple approach.Index Terms-Backward radiation, half-mode leaky-wave antennas, near-field focusing, microwave lens, sinusoidal modulation, tapered leaky mode 0018-926X (c) and Head of the Microwaves Group. His research interest includes analytical and numerical methods for planar structures, anisotropic materials, and artificial media modeling. He has coauthored more than 130 book chapters and journal papers on those topics as well as more than 260 conference contributions.He acts as reviewer for more than 40 IEEE, IEE, AIP and IoP journals and he has been member of the TPCs of a number of local and international conferences. He is now Associate Editor of the International Journal of Microwave and Wireless Technologies.

“…Such features are also extremely appealing for several near-field applications such as near-field probing, radiometry, non-invasive medical imaging, etc. [5]- [11]. The design techniques used for focusing and shaping the electromagnetic field in the near-field or Fresnel zone of an antenna stem from the seminal works in [12]- [14].…”

Section: Introductionmentioning

confidence: 99%

On the Near-Field Shaping and Focusing Capability of a Radial Line Slot Array

Ettorre

Casaletti²,

Valerio

et al. 2014

International audienceWe describe the design of a radial line slot array antenna with a shaped and focused near field. The antenna is designed in such a way to control the side lobe level and beamwidth of the normal component of the electric field with respect to the radiating aperture. The design procedure consists of two steps. In the first step, the requirements on the near-field pattern are provided over a focusing plane at a given distance from the radiating aperture. A set theoretic approach is then used to derive the aperture field distribution fitting the requirements over the near field. In the second step, the aperture field distribution is synthesized by accurately placing and sizing the slots of the antenna. The spillover efficiency is maximized during the design process. The antenna is centrally fed by a simple coaxial probe. The antenna design is validated by a prototype and measurements at 12.5 GHz