Studio dei criteri di progetto per un radar bibanda VHF+S navale

I sistemi radar imbarcati per la sorveglianza e la difesa aerea di nuova concezione dovranno essere in grado di operare in un contesto in cui lo scenario operativo assume dei connotati sempre più articolati e complessi. Nel corso dell’ultimo decennio si sono affacciati sul mercato internazionale target con proprietà stealth e velocità supersoniche, con profili di volo combinato sea-skimmer e high-diving, che al momento non sono efficacemente rivelabili dai convenzionali radar a microonde imbarcati. Le menzionate criticità sono state oggetto in particolare di studi NATO, da cui è emerso che in termini di scoperta e tracciamento si può trarre beneficio dall’impiego congiunto di bande di frequenza distinte, nella fattispecie la banda VHF e la banda S. Si sfrutterà la propagazione Surface Wave attorno ai 30 MHz per bersagli in area BHOS (Below HOrizontal Search), unitamente alla banda S, e frequenze attorno ai 150 MHz per l’area VHES (Very High Elevation Search). Rispetto alle soluzioni oggi esistenti, gli aspetti innovativi sono principalmente la caratteristica dell’impiego come gap-filler di sistemi già operativi, e la natura compatta del sistema, focalizzata sull’impiego navale. L’impiego principe, per un sistema del genere, rimarrebbe l’inserimento all’interno di un sistema di sorveglianza marittimo integrato. Il vantaggio che ne deriverebbe sarebbe pagante degli sforzi fatti: un radar multibanda su piattaforma mobile non è vincolato ad operare in una determinata zona, ma può posizionarsi in punti d’interesse strategico oppure supportare squadre navali durante la navigazione. L’obiettivo finale è di fornire un’analisi dei criteri di progetto per un sistema bibanda VHF+S navale, delineando con maggiore dettaglio i benefici dovuti all’impiego di bande distinte. Si fornisce anche uno studio delle portate ottenibili con tale sistema, dando maggior credito ad una sua realizzazione effettiva. Infine, se ne evidenziano le criticità che richiederanno un approfondimento in fase di realizzazione di un eventuale prototipo. Lo studio svolto è stato fatto analizzando l’equazione del radar, considerando attentamente i fattori peculiari del sistema multibanda. Tra gli aspetti trattati, alcuni differiscono sostanzialmente dalla progettazione classica dei radar a microonde, come la propagazione ad onda superficiale, lo studio della RCS dei bersagli di maggiore interesse (UAV, velivoli stealth, bersagli a bassa quota a velocità supersonica) e del rumore ambientale nelle due bande. Studi legati al signal processing, data fusion, eliminazione del clutter, non sono stati considerati. Si sono trascurati anche i parametri strettamente legati agli elementi radianti, quali i vantaggi di una configurazione del sistema radiante di tipo ad array ed il tempo di scansione, in quanto parametri da considerare in fasi più avanzate del progetto. Tutti i capitoli, ad eccezione del primo che introduce i sistemi multibanda, sono strutturati in modo concettualmente uguale: la prima parte contiene le basi scientifiche per inquadrare rigorosamente il problema, la parte finale contiene invece le simulazioni e le misurazioni svolte, con riferimento ai software e alle strumentazioni utilizzate, alle loro potenzialità ed ai loro limiti. Da un lato, con le simulazioni si sono analizzati contemporaneamente una varietà di parametri del sistema, potendoli far variare in un intervallo ampio di valori, permettendo l’impostazione efficace di una misura reale. Dall’altro, la misura ha permesso tanto di validare le simulazioni, quanto di evidenziare problemi reali di cui non si era tenuto conto, alimentando la sinergia fra i due diversi approcci al problema. La risposta alla possibile fattibilità del sistema proposto, è stata data in termini di probabilità di rivelazione al variare della distanza, fissati una serie di vincoli progettuali che assicurerebbero un impiego efficace a bordo, utilizzando trasmettitori commerciali con prestazioni di basso profilo. Lo studio del dimensionamento di massima del sistema rappresenta uno studio di prefattibilità e come tale deve essere considerato: una goccia nel mare della ricerca nel campo dei radar multibanda. Tuttavia, i risultati dello studio inerente la portata radar, risultano essere promettenti al fine di una realizzazione fisica del sistema: con potenze di picco massime di 3 KW è possibile rivelare piccoli bersagli, lunghi meno di 20 m, a distanze comprese fra i 20 e i 60 Km. Tali risultati preliminari sullo studio dei criteri di progetto di un radar bibanda navale danno fiducia/credito/valide basi per iniziare uno studio di prefattibilità per un progetto unico Difesa – Enti di Ricerca. Gli sviluppi futuri necessari, tracciati da questo lavoro, sono l’impostazione di uno studio congiunto e approfondito delle due bande di interesse dal punto di vista delle tecnologie avanzate di elaborazione del segnale e data fusion, e l’analisi elettromagnetica del sistema per evidenziarne le Radiation Hazard. ENGLISH VERSION: In this thesis work, under the guidance of the Radar Laboratory of CNIT (National Inter-University Consortium for Telecommunications) in Pisa and the Institute for Telecommunications and Electronics (ITE) of the Italian Navy "G. Vallauri " in Livorno, I’ve addressed various issues related to the design of a shipborne dual-band radar system. In fact, the newly developed shipborne radar systems for surveillance and air defense must be able to operate in a operational scenario takes on more and more articulate characteristics and complexities. Over the last decade it has appeared on the international market target with stealth property and supersonic speeds, combining sea-skimmer and high-diving flight profiles, which at the moment are not effectively detectable by conventional microwave radar on board. The above-mentioned problems have been subject of NATO measurement trials, tank to the working group SET (Sensors and Electronics Technology) 152, and a series of related studies of ITE, which showed that in terms of discovery and tracking can be taken benefit from the use of joint distinct frequency bands (Multiband Exploitation). From an analysis of the data collected by ITE, it has been chosen to exploit VHF band and S-band. On one hand, we'll use the Surface Wave propagation around 30\,MHz for targets in BHOs area (Below Horizontal Search), together with the S-band to improve the resolutions of the system in 3 dimensions, and on the other hand we'll use frequencies around 150MHz for the VHES area (Very High Elevation Search). Compared to existing solutions, the innovative aspects are mainly the use as gap-filler of operational systems, and the compact nature of the system, focusing on naval use. The ultimate goal is to provide an analysis of the design criteria for a dual band (VHF+S) shipborne system, outlining the benefits from the use of distinct bands. This work also provides a study of detection ranges obtainable with such a system, a necessary study for continuing a possible project. It gives even greater credit to its physical implementation on board, because is carried out a power balance with values taken by COTS (Commercial Off-The-Shelf) components. The study has been realized by an analysis of the radar equation, carefully considering factors specific to the multi-band system. Among the issues addressed, some differ substantially from the classic design of microwave radar, such as the surface wave propagation, the study on RCS of targets (UAV, stealth aircraft, low altitude targets at supersonic speed) and environmental noise in the two bands. Studies related to signal processing, data fusion and peculiarities of radiating elements, were not considered. All of them are parameters to consider in more advanced stages of the project. The answer to the possible continuation of the study of the proposed system is given in terms of probability of detection as a function of range, set a number of design constraints that would allow the use on board. The results obtained appear to be promising in terms of carry on the system design: with a peak power up to 3 kW is possible to detect targets long less than 20 m, and operating at altitudes between 10 m and 14 km, at distances between 20 and 60 Km. These preliminary results make us confident to start a research project. Future necessary development, drawn in this work, is the set up of a joint and depth study of the two bands of interest, from the point of view of advanced technologies for signal processing and data fusion. In addiction, an analysis of electromagnetic system to highlight the Radiation Hazard is needed

Interoperability Among Unmanned Maritime Vehicles: Review and First In-field Experimentation

Complex maritime missions, both above and below the surface, have traditionally been carried out by manned surface ships and submarines equipped with advanced sensor systems. Unmanned Maritime Vehicles (UMVs) are increasingly demonstrating their potential for improving existing naval capabilities due to their rapid deployability, easy scalability, and high reconfigurability, offering a reduction in both operational time and cost. In addition, they mitigate the risk to personnel by leaving the man far-from-the-risk but in-the-loop of decision making. In the long-term, a clear interoperability framework between unmanned systems, human operators, and legacy platforms will be crucial for effective joint operations planning and execution. However, the present multi-vendor multi-protocol solutions in multi-domain UMVs activities are hard to interoperate without common mission control interfaces and communication protocol schemes. Furthermore, the underwater domain presents significant challenges that cannot be satisfied with the solutions developed for terrestrial networks. In this paper, the interoperability topic is discussed blending a review of the technological growth from 2000 onwards with recent authors' in-field experience; finally, important research directions for the future are given. Within the broad framework of interoperability in general, the paper focuses on the aspect of interoperability among UMVs not neglecting the role of the human operator in the loop. The picture emerging from the review demonstrates that interoperability is currently receiving a high level of attention with a great and diverse deal of effort. Besides, the manuscript describes the experience from a sea trial exercise, where interoperability has been demonstrated by integrating heterogeneous autonomous UMVs into the NATO Centre for Maritime Research and Experimentation (CMRE) network, using different robotic middlewares and acoustic modem technologies to implement a multistatic active sonar system. A perspective for the interoperability in marine robotics missions emerges in the paper, through a discussion of current capabilities, in-field experience and future advanced technologies unique to UMVs. Nonetheless, their application spread is slowed down by the lack of human confidence. In fact, an interoperable system-of-systems of autonomous UMVs will require operators involved only at a supervisory level. As trust develops, endorsed by stable and mature interoperability, human monitoring will be diminished to exploit the tremendous potential of fully autonomous UMVs

Marine Robots for Underwater Surveillance

Abstract Purpose of Review The paper reviews the role of marine robots, in particular unmanned vehicles, in underwater surveillance, i.e. the control and monitoring of an area of competence aimed at identifying potential threats in support of homeland defence, antiterrorism, force protection and Explosive Ordnance Disposal (EOD). Recent Findings The paper explores separately robotic missions for identification and classification of threats lying on the seabed (e.g. EOD) and anti-intrusion robotic systems. The current main scientific challenge is identified in terms of enhancing autonomy and team/swarm mission capabilities by improving interoperability among robotic vehicles and providing communication networking capabilities, a non-trivial task, giving the severe limitations in bandwidth and latency of acoustic underwater messaging. Summary The work is intended to be a critical guide to the recent prolific bibliography on the topic, providing pointers to the main recent advancements in the field, and to give also a set of references in terms of mission and stakeholders' requirements (port authorities, coastal guards, navies)

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages