Analytic Design Techniques for MPT Antenna Arrays

Solar Power Satellites (SPS) represent one of the most interesting technological opportunities to provide large scale, environmentally clean and renewable energy to the Earth [1]‐[3]. A fundamental and critical component of SPSs is the Microwave Power Transmission (MPT) system, which is responsible for the delivery of the collected solar power to the ground rectenna [2]. Towards this end, the MPT array must exhibit a narrow main beam width (), a high beam efficiency (BWBE), and a low peak sidelobe level (). Moreover, reduced realization costs and weights are also necessary [3]. To reach these contrasting goals, several design techniques have been investigated including random methods [4] and hybrid deterministic‐random approaches [2][3]. On the contrary, well‐established design tools based on stochastic optimizers [5][6] are difficult to be employed, due to their high computational costs when dealing with large arrays as those of interest in SPS [3]

Generalized Analysis and Unified Design of EM Skins

A generalized formulation is derived for the analysis of the field manipulation properties of electromagnetic skins (EMSs) in the working regimes of interest for wireless communications. Based on such a theoretical framework, a unified method for the design of anomalous-reflecting and focusing EMSs is presented. Representative results, from a wide set of numerical experiments, are reported and validated with full-wave HFSS simulations to give the interested readers some insights on the accuracy, the effectiveness, and the computational efficiency of the proposed analysis/synthesis tools

An OS-agnostic approach to memory forensics

The analysis of memory dumps presents unique challenges, as operating systems use a variety of (often undocumented) ways to represent data in memory. To solve this problem, forensics tools maintain collections of models that precisely describe the kernel data structures used by a handful of operating systems. However, these models cannot be generalized and developing new models may require a very long and tedious reverse engineering effort for closed source systems. In the last years, the tremendous increase in the number of IoT devices, smart-home appliances and cloud-hosted VMs resulted in a growing number of OSs which are not supported by current forensics tools. The way we have been doing memory forensics until today, based on handwritten models and rules, cannot simply keep pace with this variety of systems. To overcome this problem, in this paper we introduce the new concept of OS-agnostic memory forensics, which is based on techniques that can recover certain forensics information without any knowledge of the internals of the underlying OS. Our approach allows to automatically identify different types of data structures by using only their topological constraints and then supports two modes of investigation. In the first, it allows to traverse the recovered structures by starting from predetermined seeds, i.e., pieces of forensics-relevant information (such as a process name or an IP address) that an analyst knows a priori or that can be easily identified in the dump. Our experiments show that even a single seed can be sufficient to recover the entire list of processes and other important forensics data structures in dumps obtained from 14 different OSs, without any knowledge of the underlying kernels. In the second mode of operation, our system requires no seed but instead uses a set of heuristics to rank all memory data structures and present to the analysts only the most ‘promising’ ones. Even in this case, our experiments show that an analyst can use our approach to easily identify forensics-relevant structured information in a truly OS-agnostic scenario

Optically-Transparent EM Skins for Outdoor-to-Indoor mm-Wave Wireless Communications

Optically-transparent opportunistic electromagnetic skins (OTO-EMSs) are proposed to enable outdoor-to-indoor (O2I) millimiter-wave (mmW) wireless communications with existing windows/glass-panels. More in detail, static passive EMSs consisting of optically-transparent conducting patterned layers attached to standard glass-panels are designed. Towards this end, both the phase coverage and the optical transparency of a meshed copper-based meta-atom printed on a non-dedicated insulated glass substrate are optimized. Successively, the feasibility of OTO-EMSs able to support mmW high-efficiency O2I transmissions along non-Snell refraction directions is numerically demonstrated

Features and Potentialities of Static Passive EM Skins for NLOS Specular Wireless Links

The ability of passive flat patterned electromagnetic skins (EMSs) to overcome the asymptotic limit of the total path attenuation (TPA) of flat metallic reflectors of arbitrary size in non-line-of-sight (NLOS) specular wireless links is assessed. Closed-form expressions for the achievable TPA in EMS-powered NLOS links as well as the condition on the panel size of EMS-screens to improve the performance of flat passive conductive screens (PCSs) with the same aperture are derived and numerically validated by considering different incidence angles, screen apertures, transmitter/receiver distances, antenna gains, meta-atom geometries, and carrier frequencies

Memory-Enhanced Dynamic Evolutionary Control of Reconfigurable Intelligent Surfaces

An innovative evolutionary method for the dynamic control of reconfigurable intelligent surfaces (RISs) is proposed. It leverages, on the one hand, on the exploration capabilities of evolutionary strategies and their effectiveness in dealing with large-scale discrete optimization problems and, on the other hand, on the implementation of memory-enhanced search mechanisms to exploit the time/space correlation of communication environments. Without modifying the base station (BS) beamforming strategy and using an accurate description of the meta-atom response to faithfully account for the micro-scale EM interactions, the RIS control (RISC) algorithm maximizes the worst-case throughput across all users without requiring that the Green's partial matrices, from the BS to the RIS and from the RIS to the users, be (separately) known/measured. Representative numerical examples are reported to illustrate the features and to assess the potentialities of the proposed approach for the RISC

Reconfigurable and Static EM Skins on Vehicles for Localization

Electromagnetic skins (EMSs) have been recently considered as a booster for wireless sensing, but their usage on mobile targets is relatively novel and could be of interest when the target reflectivity can/must be increased to improve its detection or the estimation of parameters. In particular, when illuminated by a wide-bandwidth signal (e.g., from a radar operating at millimeter waves), vehicles behave like \textit{extended targets}, since multiple parts of the vehicle's body effectively contribute to the back-scattering. Moreover, in some cases perspective deformations challenge the correct localization of the vehicle. To address these issues, we propose lodging EMSs on vehicles' roof to act as high-reflectivity planar retro-reflectors toward the sensing terminal. The advantage is twofold: \textit{(i)} by introducing a compact high-reflectivity structure on the target, we make vehicles behave like \textit{point targets}, avoiding perspective deformations and related ranging biases and \textit{(ii)} we increase the reflectivity the vehicle, improving localization performance. We detail the EMS design from the system-level to the full-wave-level considering both reconfigurable intelligent surfaces (RIS) and cost-effective static passive electromagnetic skins (SP-EMSs). Localization performance of the EMS-aided sensing system is also assessed by Cram\'er-Rao bound analysis in both narrowband and spatially wideband operating conditions

Iterative multiscaling strategy incorporated into time domain inverse scattering method for cross-borehole imaging

We consider cross-borehole imaging of buried objects embedded in a large search area by using a time domain inverse analysis. For simplicity, a two-dimensional model is examined. In order to avoid trap into false solution and enhance the achievable spatial resolution, the iterative multiscaling strategy combined with the forward-backward time-stepping method is proposed. Preliminary results show the effectiveness of proposed method.IGARSS 2011 - 2011 IEEE International Geoscience and Remote Sensing Symposium : Vancouver, BC, Canada, 2011.07.24-2011.07.2