3-D Printed All-Dielectric GRIN Lens Antenna With an Integrated Feeder

In this paper we present the design, fabrication, and experimental verification of a new type of Graded-index (GRIN) lens antenna with an integrated feeder. The continuously varying refractive index distribution is chosen appropriately to offer the rays collimation at the lens aperture. It is practically implemented by varying the material density in a host medium, thus realizing a new type of all-dielectric high gain antenna, entirely using 3D printing. This solution can find application to high gain wireless communication and measurement systems. This GRIN lens antenna is printed in one monolithic process and does not require the feeder to be placed at a focal distance, thus complying with more strict space requirements. It accepts interchangeable feeds that can cover a wide frequency range. The directivity and gain are evaluated using near-field measurements in the Ku-band. A 40% measured aperture efficiency is achieved at 14GHz. The challenges and performance limitations that come with 3D printing, as compared to the design of idealized continuous distribution GRIN lenses are discussed

On the safety design of radar based railway level crossing surveillance systems

Recent accidents experienced at railway level crossings are pushing researchers to design surveillance systems able to grant safety of passengers and structural integrity of trains at level crossings. The challenge is represented by granting at the same time an appropriate reliability, availability and maintainability degree despite the high safety requirements imposed by the application. The approach proposed in this paper takes into consideration the most common suggested standards used in designing this kind of systems and introduces new general concepts which demystify the use of such standards in actual applications. This paper illustrates the roadmap to be followed in general when designing level crossing monitoring systems, to minimize the risk due to object misdetection occurring on barrier closure when exploiting radar technology

Metasurface Antennas: New Models, Applications and Realizations

This paper presents new designs, implementation and experiments of metasurface (MTS) antennas constituted by subwavelength elements printed on a grounded dielectric slab. These antennas exploit the interaction between a cylindrical surface wave (SW) wavefront and an anisotropic impedance boundary condition (BC) to produce an almost arbitrary aperture field. They are extremely thin and excited by a simple in-plane monopole. By tailoring the BC through the shaping of the printed elements, these antennas can be largely customized in terms of beam shape, bandwidth and polarization. In this paper, we describe new designs and their implementation and measurements. It is experimentally shown for the first time that these antennas can have aperture efficiency up to 70%, a bandwidth up to 30%, they can produce two different direction beams of high-gain and similar beams at two different frequencies, showing performances never reached before

WEB PLATFORMS FOR CULTURAL HERITAGE MANAGEMENT: THE PARCO ARCHEOLOGICO DEL COLOSSEO CASE STUDY

This paper describes the digitization test of Fonte Giuturna (Giuturna spring) in the Roman Forum area, from survey to data management through the in-use monitoring system, the WebApp SyPEAH of the Parco Archeologico del Colosseo. The location of Giuturna Spring, characterized by the presence of heterogeneous archaeological remains from different ages, was surveyed in May 2022 as part of a research project that aimed to superintend the entire Cultural Heritage digitization pipeline to provide the Archaeological Park Administration the digitization guidelines as a tool to standardize future surveys and data deliveries.Inspired by the desire to build a system of protection and conservation at the service of sustainable exploitation, SyPEAH is a web platform based on open-source modules designed to manage archaeological records with a WebGIS approach. It supports the use of several 3D data formats, including point clouds. The paper focuses on the web platform, describing the web app’s main features, especially in terms of point cloud data management. Moreover, possible future development of the platform intended to implement usability for single archaeological objects is described.</p

Hyperbolic metamaterial as super absorber for scattered fields generated at its surface

We show that hyperbolic metamaterials (HMs) that exhibit hyperbolic wave-vector dispersion diagrams possess two important features related to super absorption: The total power scattered by a nanosphere is (i) greatly enhanced when placed at the HM surface, compared to other material surfaces, and (ii) almost totally directed into the HM. We show that these two features are peculiar of HM interfaces, and we support them using a spectral theory study of transverse-electric and magnetic waves scattered by a subwavelength nanosphere. We analyze the nanosphere's scattered power absorbed by various substrate configurations. We also consider various nanosphere materials. © 2012 American Physical Society

Metamaterial bricks and quantization of meta-surfaces

Controlling acoustic fields is crucial in diverse applications such as loudspeaker design, ultrasound imaging and therapy or acoustic particle manipulation. The current approaches use fixed lenses or expensive phased arrays. Here, using a process of analogue-to-digital conversion and wavelet decomposition, we develop the notion of quantal meta-surfaces. The quanta here are small, pre-manufactured three-dimensional units—which we call metamaterial bricks—each encoding a specific phase delay. These bricks can be assembled into meta-surfaces to generate any diffraction-limited acoustic field. We apply this methodology to show experimental examples of acoustic focusing, steering and, after stacking single meta-surfaces into layers, the more complex field of an acoustic tractor beam. We demonstrate experimentally single-sided air-borne acoustic levitation using meta-layers at various bit-rates: from a 4-bit uniform to 3-bit non-uniform quantization in phase. This powerful methodology dramatically simplifies the design of acoustic devices and provides a key-step towards realizing spatial sound modulators