Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

First demonstration of machine-designed ultra-flat, low-cost directive antenna

In this paper, we present a fully automated procedure for the direct design of a novel class of single‑feed flat antennas with patterning of a conductive surface. We introduce a convenient surface discretization, based on hexagonal cells, and define an appropriate objective function, including both gain and input matching requirements. The reference geometry is constituted by a very thin, single feed‑point square panel. It features a backing metal plate (“ground”) and a top conductive layer, which is automatically patterned to achieve the desired radiation and input matching properties. The process employs an evolutionary algorithm combined with a boundary element electromagnetic solver. By applying this method, we designed an antenna tailored to the 2.4 GHz ISM frequency band, with a size of 24 cm × 24 cm , i.e., 2 × 2 wavelengths and an height of 4 mm, or 0.03 wavelengths. Measured data confirmed the expected high gain (13 dBi), with a remarkable aperture efficiency (higher than 50%, including losses), thus validating the proposed approach

Beam Scanning Leaky-Wave Antenna with a Reconfigurable Impedance Plane

An electronically-reconfigurable leaky-wave antenna based on metasurfaces is designed and implemented. This innovative antenna consists of a multilayered structure with two (metasurface) impedance planes. The beam scanning at fixed frequency is achieved by electronically tuning the surface impedance of the lower plane using voltage-controlled varactor diodes. The rationale of this solution is that a variation in the impedance profile of the antenna in the direction transversal to propagation affects the phase velocity of the leaky wave and therefore the beam direction

Field and Temperature Shaping for Microwave Hyperthermia: Recent Treatment Planning Tools to Enhance SAR-Based Procedures

The aim of the article is to provide a summary of the work carried out in the framework of a research project funded by the Italian Ministry of Research. The main goal of the activity was to introduce multiple tools for reliable, affordable, and high-performance microwave hyperthermia for cancer therapy. The proposed methodologies and approaches target microwave diagnostics, accurate in vivo electromagnetic parameters estimation, and improvement in treatment planning using a single device. This article provides an overview of the proposed and tested techniques and shows their complementarity and interconnection. To highlight the approach, we also present a novel combination of specific absorption rate optimization via convex programming with a temperature-based refinement method implemented to mitigate the effect of thermal boundary conditions on the final temperature map. To this purpose, numerical tests were carried out for both simple and anatomically detailed 3D scenarios for the head and neck region. These preliminary results show the potential of the combined technique and improvements in the temperature coverage of the tumor target with respect to the case wherein no refinement is adopted

Large Horizontal Near-field Scanner based on a Non-tethered Unmanned Aerial Vehicle

A horizontal planar scanner with an approximate size of 40 m x 40 m has been implemented using the Unmanned Aerial Vehicle (UAV) technology. The UAV is not wired to the ground to maintain the flexibility and short setup time of a non-tethered flight. In this configuration, the UAV-mounted continuous-wave source is not phase-locked to the on-the-ground receiver. A dual-polarized reference antenna placed on the ground is hence used to retrieve the relevant phase information. The presented approach has been applied on the Pre - Aperture Array Verification System (Pre -AAVS1) of the Square Kilometre Array, which is a digital beamformed array with 16 active elements. An inverse source technique has been applied on measured Near-Field (NF) data acquired on two different sets of points (one for each electric field component) from all the receiver channels. In this way, Embedded Element Patterns (EEPs), array calibration coefficients and pattern have been determined from NF data only. The achieved results have been validated using a complementary set of Far-Field (FF) measurements and simulations

Hybrid Measurement/Simulation Approaches for Antenna Testing

This work investigate the performance of a set of techniques to reduce the number of measurement points and then the associated measurement time, by introducing a set of algorithms able to perform fast antenna testing by mixing together measurements and simulations. More specifically, the following points will be investigated: 1) introduction of a new hybrid system that joins suitable simulations of the Device Under Test (DUT) and measured data; 2) definition of suitable metrics to evaluate the performance of the reconstructions; 3) introduction of a probe compensation technique able to take into account of the effects that a probe can introduce (due to the close distance between DUT and probe itself); 4) introduction of Reduced Order Model (ROM) techniques applied to the specific problem of antenna placing

Hybrid Measurement/Simulation Approaches for Antenna Testing

This work investigate the performance of a set of techniques to reduce the number of measurement points and then the associated measurement time, by introducing a set of algorithms able to perform fast antenna testing by mixing together measurements and simulations. More specifically, the following points will be investigated: 1) introduction of a new hybrid system that joins suitable simulations of the Device Under Test (DUT) and measured data; 2) definition of suitable metrics to evaluate the performance of the reconstructions; 3) introduction of a probe compensation technique able to take into account of the effects that a probe can introduce (due to the close distance between DUT and probe itself); 4) introduction of Reduced Order Model (ROM) techniques applied to the specific problem of antenna placing