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In this work we present an automatic, deterministic procedure to fully design an isotropic metasurface antenna, self-consistently including the metallic feeding structure. The impedance pattern has full spatial variability in two dimensions, to allow designs otherwise difficult. The design is based on the integral-equation formulation with a current-only approach, in which the surface impedance profile is derived only after the optimal current is found; this allows to avoid the solution of the forward problem at all steps of the algorithm, with a drastic reduction of computational resources; it does not require any assumption on the impedance profile. We also show how a 3-D feed can be accounted for in a hybrid scheme partially employing commercial 3-D simulation software. Application examples address center-fed circular metasurface antennas, in which the feed is not connected to the metasurface, and rectangular “strip-like” leaky wave antennas (LWAs) where the metasurface is electrically connected to the feeding surface. In all cases, the design is carried out up to the final layout, and the full antenna is simulated to verify the design.

An electromagnetics-aware path for drone-based near-field (NF) antenna measurements is implemented in an outdoor experimentation. This technique allows us to significantly reduce the scan duration with respect to a standard half-wavelength NF scanning, using knowledge of the antenna under test (AUT) electrical size only. The validity of our approach is corroborated with planar outdoor NF measurements performed with an untethered drone transmitting at 750 MHz. To deal with the absence of phase coherence, the phase information is retrieved from a reference antenna, while a software-defined radio (SDR) having four super-heterodyne receiving channels is used to properly sample the high-dynamic signals resulting from the large scanning surface.

Directed Energy Deposition (DED) is one of the most challenging metal additive manufacturing (AM) processes on the market, still one of its main drawbacks is the poor surface characteristic. Laser polishing is an emerging technique for surface finishing of AM components, that can be easily integrated in laser powder directed energy deposition (LP-DED). Laser polishing can be used for reaching inner parts of complex shaped component during LP-DED production. In this study, an exploratory analysis on the most significant parameters involved in the laser finishing process is performed, providing a robust base for further optimization studies in the field.

We present a 3-D method to numerically design a realizable metasurface, which transforms a given incident field into a radiated field that satisfies mask-type (inequality) constraints. The method is based on an integral equation formulation, with local impedance boundary condition (IBC) approximation. The procedure yields the spatial distribution of the impedance, yet the process involves the synthesis of the equivalent current only. This current is constrained to correspond to a realizable surface impedance, i.e., passive, lossless, and with reactance values bounded by practical realizability limits. The current-based design avoids any solution to the forward problem, and the impedance is obtained from the synthesized current only at the end of the process. The procedure is gradient-based, with the gradient expressed in closed form. This allows handling large metasurfaces, with full spatial variability of the impedance in two dimensions. The method requires no a priori information, and all relevant operations in the iterative process can be evaluated with $\boldsymbol { O}(N~\log~{N})$ complexity. Application examples concentrate on the case of on-surface excitation and far-field (FF) pattern specifications; they show designs of circular and rectangular metasurface antennas of 20 wavelengths in size, with pencil- and shaped-beam patterns, and for both circular and linear polarizations.

We describe a method to use numerical simulations concurrently with measurements (near-field data) to characterize the radiation properties of an antenna (far-field) with a strongly reduced number of samples. Both the simulations and experimental data are dealt with as sources of information toward obtaining the desired characterization. Simulations compensate for data scarceness, allowing to obtain an accurate characterization with fewer data than with measurements only, and the few measured data allow the comprehensive numerical proxy to get tuned to the true antenna under test (AUT). The method uses partial knowledge of the antenna and leverages accelerated asymptotic numerical methods to perform the numerical simulations needed by the algorithm. We report experimental tests of performance, both in terms of accuracy and speed-up with respect to the classical methods, with reflector antennas up to 27 wavelength. It is important to note that good results are obtained both when samples are taken on irregular optimized grids and on regular grids usually resulting from the conventional measurement rigs.

Additive Manufacturing (AM) offers great potentialities in the medical sector, particularly when part customization is sought after. Maxillofacial surgery has to deal with complex bone fractures and facial reconstructions, hence the need of metallic prostheses to help in the process of bone growth and fracture healing. Commercial prostheses, even if available in different sizes, might not fit the patient's anatomy, and thus should be adapted directly in the operating room. This paper provides an insight on how AM approach, by designing and producing customized prosthesis from computer tomography scan data, can lead to predictable and reliable results reducing the stress on both surgeons and patients.

Background: High-resolution CT (HRCT) scanning plays an important role in the diagnosis of diffuse cystic lung diseases (DCLDs). However, its role in the clinical evaluation of patients affected by DCLD [...]

Generative Design is a powerful tool allowing to fully exploit Additive Manufacturing potential. Topology Optimization, already established approach, requires an initial shape where material is removed until the desired result is reached. Generative Design presents a more complex approach, receiving several inputs such as objective, constraints, material and manufacturing technique used, it proposes a series of possible outcomes. Designer's role moves from creating the component shape from scratches to choose the best fitting option for the specific application. Using a reference case study, a plausible framework, describing how to properly select the final model, is investigated.

Microwave hyperthermia aims at selectively heating cancer cells to a supra-physiological temperature. For non-superficial tumors, this can be achieved by means of an antenna array equipped with a proper cooling system (the water bolus) to avoid overheating of the skin. In patient-specific treatment planning, antenna feedings are optimized to maximize the specific absorption rate (SAR) inside the tumor, or to directly maximize the temperature there, involving a higher numerical cost. We present here a method to effect a low-complexity temperature-based planning. It arises from recognizing that SAR and temperature have shifted peaks due to thermal boundary conditions at the water bolus and for physiological effects like air flow in respiratory ducts. In our method, temperature focusing on the tumor is achieved via a SAR-based optimization of the antenna excitations, but optimizing its target to account for the cooling effects. The temperature optimization process is turned into finding a SAR peak position that maximizes the chosen temperature objective function. Application of this method to the 3D head and neck region provides a temperature coverage that is consistently better than that obtained with SAR-optimization alone, also considering uncertainties in thermal parameters. This improvement is obtained by solving the bioheat equation a reduced number of times, avoiding its inclusion in a global optimization process.