arXiv subjects

Filippo Costa

Publications and source records attributed to Filippo Costa.

16 recordsLinked to original sources

arXiv2026

RIS-aided Radar Detection Architectures with Application to Low-RCS Targets

In this paper, we address the radar detection of low observable targets with the assistance of a reconfigurable intelligent surface (RIS). Instead of using a multistatic radar network as counter-stealth strategy with its synchronization, costs, phase coherence, and energy consumption issues, we exploit a RIS to form a joint monostatic and bistatic configuration that can intercept the energy backscattered by the target along irrelevant directions different from the line-of-sight of the radar. Then, this energy is redirected towards the radar that capitalizes all the backscattered energy to detect the low observable target. To this end, five different detection architectures are devised that jointly process monostatic and bistatic echoes and exhibit the constant false alarm rate property at least with respect to the clutter power. To support the practical implementation, we also provide a guideline for the design of a RIS that satisfies the operating requirements of the considered application. The performance analysis is carried out in comparison with conventional detectors and shows that the proposed strategy leads to effective solutions to the detection of low observable targets.

eess.SP↗

arXiv2025

Continuous signal sparse encoding using analog neuromorphic variability

Achieving fast and reliable temporal signal encoding is crucial for low-power, always-on systems. While current spike-based encoding algorithms rely on complex networks or precise timing references, simple and robust encoding models can be obtained by leveraging the intrinsic properties of analog hardware substrates. We propose an encoding framework inspired by biological principles that leverages intrinsic neuronal variability to robustly encode continuous stimuli into spatio-temporal patterns, using at most one spike per neuron. The encoder has low model complexity, relying on a shallow network of heterogeneous neurons. It relies on an internal time reference, allowing for continuous processing. Moreover, stimulus parameters can be linearly decoded from the spiking patterns, granting fast information retrieval. Our approach, validated on both analog neuromorphic hardware and simulation, demonstrates high robustness to noise, spike jitter, and reduced heterogeneity. Consistently with biological observations, we observed the spontaneous emergence of patterns with stereotyped spiking order. The proposed encoding scheme facilitates fast, robust and continuous information processing, making it well-suited for low-power, low-latency processing of temporal data on analog neuromorphic substrates.

cs.NE↗

arXiv2023

Design and simulation of a transmon qubit chip for Axion detection

Quantum Sensing is a rapidly expanding research field that finds one of its applications in Fundamental Physics, as the search for Dark Matter. Devices based on superconducting qubits have already been successfully applied in detecting few-GHz single photons via Quantum Non-Demolition measurement (QND). This technique allows us to perform repeatable measurements, bringing remarkable sensitivity improvements and dark count rate suppression in experiments based on high-precision microwave photon detection, such as for Axions and Dark Photons search. In this context, the INFN Qub-IT project goal is to realize an itinerant single-photon counter based on superconducting qubits that will exploit QND for enhancing Axion search experiments. In this study, we present Qub-IT's status towards the realization of its first superconducting qubit device, illustrating design and simulation procedures and the characterization of fabricated Coplanar Waveguide Resonators (CPWs) for readout. We match target qubit parameters and assess a few-percent level agreement between lumped and distributed element simulation models. We reach a maximum internal quality factor of 9.2x10^5 for -92 dBm on-chip readout power.

quant-ph↗

arXiv2021

Electromagnetic Model of Reflective Intelligent Surfaces

An accurate and simple analytical model for the computation of the reflection amplitude and phase of Reconfigurable Intelligent Surfaces is presented. The model is based on a transmission-line circuit representation of the RIS which takes into account the physics behind the structure including the effect of all relevant geometrical and electrical parameters. The proposed representation of the RIS allows to take into account the effect of incidence angle, mutual coupling among elements and the effect of the interaction of the periodic surface with the RIS ground plane. It is shown that the proposed approach allows to design a physically realisable RIS without recurring to onerous electromagnetic simulations. The proposed model aims at filling the gap between RIS assisted communications algorithms and physical implementation issues which determine realistic performance of these surfaces.

eess.SP↗

arXiv2020

Radar Cross Section of Chipless RFID tags and BER Performance

The performance of different chipless RFID tag topologies are analysed in terms of Radar Cross Section (RCS) and Bit Error Rate (BER). It is shown that the BER is mainly determined by the tag Radar Cross Section (RCS) once that a standard reading scenario is considered and a fixed size of the tag is chosen. It is shown that the arrangement of the resonators in the chipless tag plays a crucial role in determining the cross-polar RCS of the tag. The RCS of the tag is computed theoretically by using array theory where each resonator is treated as a separate scatterer completely characterized by a specific reflection coefficient. Several resonators arrangements (periodic and non-periodic) are compared, keeping the physical area of the tag fixed. Theoretical and experimental analysis demonstrate that the periodic configuration guarantees the maximum achievable RCS thus providing a global lower BER of the chipless RFID communication system. We believe that the BER is the more meaningful and fair figure of merit for comparing the performance of different tags than bit/cm2 or bit/Hz since the increase of encoded information of the tag is useful only if it can be correctly decoded.

physics.app-ph↗

arXiv2020

Systematic Design of Transmission-type Polarization Converters Comprising Multi-layered Anisotropic Metasurfaces

A simple but efficient approach for the synthesis of transmission-type wideband polarization converters is presented. The proposed configuration comprises multilayer metasurfaces including resonant particles which are progressively rotated layer by layer. The progressive rotation of the particles allows for a polarization conversion over a large frequency band. The polarizing structure is efficiently designed and optimized through a transmission line model approach handling the cascade of anisotropic impedance layers and dielectrics. An optimized 8-layers design based on gradually rotated dipole resonators is presented as a proof of concept. The results obtained through the efficient transmission line model are compared with full-wave simulations once that the structure was optimized showing satisfactory agreement. A prototype of the wideband polarization converter has been fabricated and measured.

physics.app-ph↗

arXiv2020

The ReadoutCard userspace driver for the new ALICE $O^2$ computing system

The ALICE (A Large Ion Collider Experiment) experiment focuses on the study of the quark-gluon plasma as a product of heavy-ion collisions at the CERN LHC (Large Hadron Collider). During the Long Shutdown 2 of the LHC in 2019-2020, a major upgrade is underway in order to cope with a hundredfold input data rate increase with peaks of up to 3.4 TB/s. This upgrade includes the new Online-Offline computing system called O2. The O2 readout chain runs on commodity Linux servers equipped with custom PCIe FPGA-based readout cards; the PCIe v3 x16, Intel Arria 10-based CRU (Common Readout Unit) and the PCIe v2 x8, Xilinx Vertex6-based CRORC (Common ReadOut Receiver Card). Access to the cards is provided through the O2 ReadoutCard userspace driver which handles synchronisation and communication for DMA transfers, provides BAR access, and facilitates card configuration and monitoring. The ReadoutCard driver is the lowest-level interface to the readout cards within O2 and is in use by all central systems and detector teams of the ALICE experiment. This communication presents the architecture of the driver, and the suite of tools used for card configuration and monitoring. It also discusses its interaction with the tangent subsystems within the O2 framework.

physics.ins-det↗

arXiv2020

A Simple Equivalent Circuit Approach for Anisotropic Frequency Selective Surfaces and Metasurfaces

An equivalent circuit model for Frequency Selective Surfaces (FSS) comprising anisotropic elements is presented. The periodic surface is initially simulated with an arbitrary azimuthal incidence angle and its surface impedance matrix is derived. The impedance matrix is subsequently rotated by an angle $\varphi^{rot}$ on the crystal axes $\chi_1$, $\chi_2$ thus nullifying its extra diagonal terms. The rotation angle $\varphi^{rot}$ is derived according to the spectral theorem by using the terms of the matrix initially extracted. The diagonal terms of the rotated matrix, that is, the impedances $Z_{\chi_1}$ and $Z_{\chi_2}$, are finally matched with simple LC networks. The circuit model representation of the anisotropic element can be used to analyse anisotropic FSSs rotated by a generic azimuth angle. The methodology provides a compact description of generic FSS elements with only five parameters: the lumped parameters of the LC network $L_{\chi_1}$, $C_{\chi_1}$, $L_{\chi_2}$, $C_{\chi_2}$ and the rotation angle $\varphi^{rot}$. The circuit model can take into account the presence of dielectric substrates close to the FSS or a variation of the FSS periodicity without additional computational efforts. The equivalent circuit model is finally applied to the design of two transmitting polarization converts based on anisotropic metasurfaces.

physics.app-ph↗

arXiv2018

Chipless Dielectric Constant Sensor for Structural Health Testing

A low-cost chipless RFID sensor tag to determine the dielectric properties of materials is presented. The sensor is based on a depolarizing dipole resonator loaded with printed capacitors whose capacitance depends on the permittivity of the material located on contact with the tag. The permittivity is obtained from the shift of the resonance frequency. The resonator is tested both individually as well as placed on a periodic arrangement so as to form a frequency selective structure (FSS) to increase the cross- polar radar cross section, thus facilitating the tag detection. The proposed structure and measurement procedure is particularly suitable for the characterization of civil materials as a nondestructive testing (NDT).

physics.app-ph↗

arXiv2017

An Inkjet Printed Chipless RFID Sensor for Wireless Humidity Monitoring

A novel chipless RFID humidity sensor based on a finite Artificial Impedance Surface (AIS) is presented. The unit cell of the AIS is composed of three concentric loops thus obtaining three deep and high Q nulls in the electromagnetic response of the tag. The wireless sensor is fabricated using low-cost inkjet printing technology on a thin sheet of commercial coated paper. The patterned surface is placed on a metal backed cardboard layer. The relative humidity information is encoded in the frequency shift of the resonance peaks. Varying the relative humidity level from 50% to 90%, the frequency shift has proven to be up to 270MHz. The position of the resonance peaks has been correlated to the relative humidity level of the environment on the basis of a high number of measurements performed in a climatic chamber, specifically designed for RF measurements of the sensor. A very low error probability of the proposed sensor is demonstrated when the device is used with a 10% RH humidity level discrimination.

physics.app-ph↗

arXiv2017

The ALICE O2 common driver for the C-RORC and CRU read-out cards

ALICE (A Large Ion Collider Experiment) is the heavy-ion detector designed to study the strongly interacting state of matter realized in relativistic heavy-ion collisions at the CERN Large Hadron Collider (LHC). A major upgrade of the experiment is planned during the 2019-2020 long shutdown. In order to cope with a data rate 100 times higher than during LHC Run 1 and with the continuous read-out of the Time Projection Chamber (TPC), it is necessary to upgrade the Online and Offline Computing to a new common system called O2 . The O2 read- out chain will use commodity x86 Linux servers equipped with custom PCIe FPGA-based read- out cards. This paper discusses the driver architecture for the cards that will be used in O2 : the PCIe v2 x8, Xilinx Virtex 6 based C-RORC (Common Readout Receiver Card) and the PCIe v3 x16, Intel Arria 10 based CRU (Common Readout Unit). Access to the PCIe cards is provided via three layers of software. Firstly, the low-level PCIe (PCI Express) layer responsible for the userspace interface for low-level operations such as memory mapping the PCIe BAR (Base Address Registers) and creating scatter-gather lists, which is provided by the PDA (Portable Driver Architecture) library developed by the Frankfurt Institute for Advanced Studies (FIAS). Above that sits our userspace driver which implements synchronization, controls the read-out card -- e.g. resetting and configuring the card, providing it with bus addresses to transfer data to and checking for data arrival -- and presents a uniform, high-level C++ interface that abstracts over the differences between the C-RORC and CRU. This interface -- of which direct usage is principally intended for high-performance read-out processes -- allows users to configure and use the various aspects of the read-out cards, such as configuration, DMA transfers and commands to the front-end. [...]

physics.ins-det↗

arXiv2012

A Circuit-based Model for the Interpretation of Perfect Metamaterial Absorbers

A popular absorbing structure, often referred to as Perfect Metamaterial Absorber, comprising metallic periodic pattern over a thin low-loss grounded substrate is studied by resorting to an efficient transmission line model. This approach allows the derivation of simple and reliable closed formulas describing the absorption mechanism of the subwavelength structure. The analytic form of the real part of the input impedance is explicitly derived in order to explain why moderate losses of the substrate is sufficient to achieve matching with free space, that is, perfect absorption. The effect of the constituent parameters for tuning the working frequency and tailoring the absorption bandwidth is addressed. It is also shown that the choice of highly capacitive coupled elements allows obtaining the largest possible bandwidth whereas a highly frequency selective design is achieved with low capacitive elements like a cross array. Finally, the angular stability of the absorbing structure is investigated.

physics.class-ph↗

arXiv2010

Analysis and Design of Ultra Thin Electromagnetic Absorbers Comprising Resistively Loaded High Impedance Surfaces

High-Impedance Surfaces (HIS) comprising lossy Frequency Selective Surfaces (FSS) are employed to design thin electromagnetic absorbers. The structure, despite its typical resonant behavior, is able to perform a very wideband absorption in a reduced thickness. Losses in the frequency selective surface are introduced by printing the periodic pattern through resistive inks and hence avoiding the typical soldering of a large number of lumped resistors. The effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model. It is shown that the optimum value of surface resistance is affected both by substrate parameters (thickness and permittivity) and by FSS element shape. The equivalent circuit model is then used to introduce the working principles of the narrowband and the wideband absorbing structure and to derive the best-suited element for wideband absorption. Finally, the experimental validation of the presented structures is presented.

physics.class-ph↗

arXiv2010

On the Bandwidth of High-Impedance Frequency Selective Surfaces

In this letter, the bandwidth of high-impedance surfaces (HISs) is discussed by an equivalent circuit approach. Even if these surfaces have been employed for almost 10 years, it is sometimes unclear how to choose the shape of the frequency selective surface (FSS) on the top of the grounded slab in order to achieve the largest possible bandwidth. Here, we will show that the conventional approach describing the HIS as a parallel connection between the inductance given by the grounded dielectric substrate and the capacitance of the FSS may induce inaccurate results in the determination of the operating bandwidth of the structure. Indeed, in order to derive a more complete model and to provide a more accurate estimate of the operating bandwidth, it is also necessary to introduce the series inductance of the FSS.We will present the explicit expression for defining the bandwidth of a HIS, and we will show that the reduction of the FSS inductance results in the best choice for achieving wide operating bandwidth in correspondence with a given frequency.

physics.ins-det↗

arXiv2009

An Active High Impedance Surface for Low Profile Tunable and Steerable Antennas

In this letter, an approach for designing a tunable and steerable antenna is presented. The antenna model is based on a wideband bow-tie radiating element mounted above an active Artificial Magnetic Conductor (AMC). The AMC geometry consists of a Frequency Selective Surface (FSS) printed on a thin grounded dielectric slab in which some chip-set varactor diodes are placed between the metallic elements and the backing plane through vias. The resulting antenna can be tuned over the S-Band by simply changing all varactor capacitances through an appropriate biasing voltage. Moreover, this structure can operate a beam scanning over each working frequency by applying an appropriate biasing voltage to the active elements of the AMC surface in accordance to leaky radiation principles. The low profile active antenna is characterized by an overall thickness of 5.32 mm, which corresponds to approximately lambda/24 at the centre of the operating band.

physics.class-ph↗

arXiv2008

A Thin Electromagnetic Absorber for Wide Incidence Angles and Both Polarizations

In this paper a planar electromagnetic absorber is introduced whose performance is maintained over a wide change of the incidence angle for both TE and TM polarization. The absorber comprises an array of patches over a grounded dielectric slab, with clear advantage in terms of manufacturability. It is shown that a high value of the relative permittivity of the substrate is essential for the operation of the absorber. The main contribution of the paper is to demonstrate and practically use the presence of an additional resonance of high-impedance surfaces when the plasma frequency of the wire medium comprising metallic vias in the dielectric substrate is close to the original resonance of the high-impedance surface. The presence of the vias between FSS and the ground plane is discussed both for the case of a high-permittivity absorber and for a low permittivity one. The radius of the vias influences the oblique incidence TM absorption, and when properly designed, the insertion of the vias result in bandwidth enlargement and higher absorption.

physics.class-ph↗