Tecniche di progetto di sistemi radar per la rivelazione di detriti spaziali

L’obiettivo di questo lavoro sarà quindi quello di inquadrare il problema relativo agli scenari attuali e alle proiezioni future degli space debris individuando quindi quelli scenari considerati di maggior interesse. Successivamente verranno presentate una serie di simulazioni, adottando un software della NASA, che forniranno dati concreti sulla popolazione dei detriti relativamente alle ipotesi fatte in precedenza. La chiave di questa tesi sarà però la simulazione della RCS (Radar Cross Section) dei detriti orbitanti descritta nel terzo capitolo e che ci fornirà un possibile ventaglio di tali valori espressi in dBsm. Tali simulazioni verranno fatte per semplici strutture al variare della frequenza e dell’angolo di vista; molta importanza verrà data alla simulazione della sfera che permetterà di valutare la correttezza di tali simulazioni. Poi, anche mediante lo studio di alcuni sensori esistenti, si andranno a ricercare le caratteristiche ottimali per la loro rivelazione. Verranno infine individuate alcune frequenze ottime per la rivelazione degli space debris e che verranno usate in seguito come base per la stima dei parametri del radar. Come appena accennato si studieranno le caratteristiche di alcuni elementi radianti di possibile utilizzo valutandone geometrie e guadagni e verranno quindi esaminati tutti i parametri del radar alle frequenze scelte. Questo ci porterà alla fase del lavoro che prevede l’inserimento di tutti i dati fin qui collezionati nell’equazione del radar per stilare una tabella sulle potenze di picco necessarie per effettuare la rivelazione di detriti di determinata taglia, ad una data frequenza, in regioni di spazio ben precise e con caratteristiche altrettanto precise sul tipo di sensore. La fase conclusiva del lavoro prevede uno studio sulle caratteristiche dei sistemi radar di tipo bistatici (con estensione al caso multistatico) per la rivelazione dei detriti spaziali. Tale trattazione risulterà necessaria per comprendere come poter applicare le caratteristiche di questi sistemi in un contesto nazionale per la realizzazione di una “Network” in grado di coadiuvare lo studio di questo fenomeno

Photonic Technologies for Radar and Telecomunications Systems

The growing interest in flexible architectures radio and the recent progress in the high speed digital signal processor make a software defined radio system an enabling technology for several digital signals processing architecture and for the flexible signal generation. In this direction wireless radar\telecommunications receiver with digital backend as close as possible to the antenna, as well as the software defined signal generation, reaches several benefits in term of reconfigurabilty, reliability and cost with respect to the analogical front-ends. Unfortunately the present scenario ensures direct sampling and digital downconversion only at the intermediate frequency. Therefore these kinds of systems are quite vulnerable to mismatches and hardware non-idealities in particular due to the mixers stages and filtering process. Furthermore, since the limited input bandwidth, speed and precision of the analog to digital converters represent the main digital system‘s bottleneck, today‘s direct radio frequency sampling is only possible at low frequency. On the other hand software defined signals can be generated exploiting direct digital synthesizers followed by an up-conversion to the desired carrier frequency. State-of-the-art synthesizers (limited to few GHz) introduce quantization errors due to digital-to-analog conversion, and phase errors depending on the phase stability of their internal clock. In addition the high phase stability required in modern wireless systems (such as radar systems) is becoming challenging for the electronic RF signal generation, since at high carrier frequency the frequency multiplication processes that are usually exploited reduce the phase stability of the original RF oscillators. Over the past 30 years microwave photonics (MWP) has been defined as the field that study the interactions between microwave and optical waves and their applications in radar and communications system as well as in hybrid sensor‘s instrumentation. As said before software defined radio applications drive the technological development trough high speed\bandwidth and high dynamic range systems operating directly in the radio frequency domain. Nowadays, while digital electronics represent a limit on system performances, photonic technologies perfectly engages the today‘s system needs and offers promising solution thanks to its inherent high frequency and ultrawide bandwidth. Moreover photonic components with very high phase coherence guarantees highly stable microwave carriers; while strong immunity to the electromagnetic interference, low loss and high tunability make a MWP system robust, flexible and reliable. Historical research and development of MWP finds space in a wide range of applications including the generation, distribution and processing of radio frequency signals such as, for example, analog microwave photonic link, antenna remoting, high frequency and low noise photonic microwave signal generation, photonic microwave signal processing (true time delay for phased array systems, tunable high Q microwave photonic filter and high speed analog to digital converters) and broadband wireless access networks. Performances improvement of photonic and hybrid devices represents a key factor to improve the development of microwave photonic systems in many other applications such as Terahertz generation, optical packet switching and so on. Furthermore, advanced in silicon photonics and integration, makes the low cost complete microwave photonic system on chip just around the corner. In the last years the use of photonics has been suggested as an effective way for generating low phase-noise radio frequency carriers even at high frequency. However while a lot of efforts have been spent in the photonic generation of RF carriers, only few works have been presented on reconfigurable phase coding in the photonics-based signal generators. In this direction two innovative schemes for optically generate multifrequency direct RF phase modulated signals have been presented. Then we propose a wideband ADC with high precision and a photonic wireless receiver for sparse sensing. This dissertation focuses on microwave photonics for radar and telecommunications systems. In particular applications in the field of photonic RF signal generation, photonic analog to digital converters and photonic ultrawideband radio will be presented with the main objective to overcome the limitations of pure electrical systems. Schemes and results will be further detailed and discussed. The dissertation is organized as follows. In the first chapter an overview of the MWP technologies is presented, focusing the attention of the limits overcame by using hybrid optoelectronic systems in particular field of applications. Then optoelectronic devices are introduced in the second chapter to better understand their role in a MWP system. Chapters 3,4, and 5 present results on photonic microwave signal generation, photonic wideband analog to digital converters and photonic ultrawideband up\down converter for both radar and telecommunications applications. Finally in the chapter 6 an overview of the photonic radar prototype is given

A fully photonics-based coherent radar system

The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion. Until now, the photonics-based generation and detection of radio-frequency signals have been studied separately and have not been tested in a radar system. Here we present the development and the field trial results of a fully photonics-based coherent radar demonstrator carried out within the project PHODIR. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system

Molecular characterization of Babesia and Theileria species in ticks collected in the outskirt of Monte Romano, Lazio Region, Central Italy

In 2012-2013, an investigation was carried out in the Viterbo province, Lazio region, on ticks and tick-borne Apicomplexan protozoa of the Babesia and Theileria genera. This followed the reporting of high density of ticks by soldiers operating in a military shooting range, and the signaling by owners and local veterinary authorities of several cases of babesiosis among cattle. A total of 422 ticks were collected from 35 heads, whereas 96 ticks were collected by dragging. Ticks were identified as Rhipicephalus (Boophilus) annulatus Say (n=373), Rhipicephalus bursa Canestrini & Fanzago (n=63), Rhipicephalus sanguineus/turanicus (n=32), Hyalomma marginatum Koch (n=49) and Dermacentor marginatus Sulzer, 1776 (n=1). A randomly selected sample of ticks (235 from animals and 36 by dragging) was analyzed using molecular methods to detect species of Babesia and Theileria. In total, 11 ticks collected from animals (4.7%) and two ticks (5.5%) collected by dragging were positive. Sequencing of PCR products of the small subunit ribosomal RNA gene revealed Babesia caballi (n=2), Babesia bigemina (n=3), Theileria sergenti/buffeli/orientalis (n=7) and Theileria equi (n=1). None of the detected species has been associated with human infection

Detection of tick-borne pathogens in ticks collected in the suburban area of Monte Romano, Lazio Region, Central Italy

Background. A study on tick species characterization and tick borne pathogens detection was performed within a survey conducted during 2012 and 2013 in the Viterbo province (Lazio Region, Central Italy). Seven sites were selected for the study investigation, including two farms and a military zone. Methods. A total of 255 ticks, Rhipicephalus (Boophilus) annulatus (n =215), Rhipicephalus bursa (n = 28), and Hyalomma marginatum (n = 12) were screened individually by molecular methods for the tick borne bacterial agents: Borrelia burgdorferi sensu lato group, Bartonella spp., Coxiella burnetii, Ehrlichia spp., Francisella spp., and Rickettsia spp. Results and Conclusion. Overall, 182 ticks (71%) were infected with one pathogen but co-infections were also found. Tick borne pathogens identified were C. burnetii, B. burgdorferi s.l.., Bartonella spp., Rickettsia spp., Francisella spp., and Ehrlichia spp. In R. bursa and H. marginatum, the presence of B. burgdorferi s.l. was positively correlated with that of C. burnetii, Rickettsia spp., and Bartonella spp. and their coinfection probabilities were 29.8%, 22.7% and 11.7%, respectively. The Probability of coinfection for Francisella spp. and Rickettsia spp. and for Francisella spp. and Bartonella spp. was 14.9% and 17.9%, respectively. In R. (Boophilus) annulatus, the probability of coinfection between C. burnetii and B. burgdorferi s.l. was 11.3%, while those between C. burnetii and Bartonella and between B. burgdorferi s.l. and Bartonella were 0.8%. Further studies are needed in order to assess the risk associated with these tick-borne pathogens, somewhat unusual in Central Italy

Insights into the Complex Formed by Matrix Metalloproteinase-2 and Alloxan Inhibitors: Molecular Dynamics Simulations and Free Energy Calculations

Matrix metalloproteinases (MMP) are well-known biological targets implicated in tumour progression, homeostatic regulation, innate immunity, impaired delivery of pro-apoptotic ligands, and the release and cleavage of cell-surface receptors. Hence, the development of potent and selective inhibitors targeting these enzymes continues to be eagerly sought. In this paper, a number of alloxan-based compounds, initially conceived to bias other therapeutically relevant enzymes, were rationally modified and successfully repurposed to inhibit MMP-2 (also named gelatinase A) in the nanomolar range. Importantly, the alloxan core makes its debut as zinc binding group since it ensures a stable tetrahedral coordination of the catalytic zinc ion in concert with the three histidines of the HExxHxxGxxH metzincin signature motif, further stabilized by a hydrogen bond with the glutamate residue belonging to the same motif. The molecular decoration of the alloxan core with a biphenyl privileged structure allowed to sample the deep S1′ specificity pocket of MMP-2 and to relate the high affinity towards this enzyme with the chance of forming a hydrogen bond network with the backbone of Leu116 and Asn147 and the side chains of Tyr144, Thr145 and Arg149 at the bottom of the pocket. The effect of even slight structural changes in determining the interaction at the S1′ subsite of MMP-2 as well as the nature and strength of the binding is elucidated via molecular dynamics simulations and free energy calculations. Among the herein presented compounds, the highest affinity (pIC50 = 7.06) is found for BAM, a compound exhibiting also selectivity (>20) towards MMP-2, as compared to MMP-9, the other member of the gelatinases

Photonics for radar networks and electronic warfare systems

This book outlines the potential for microwave photonics in radar and electronic warfare systems, covering basic concepts and functions, comparing performance with conventional systems, describing its impact on digital signal processing, and exploring integration issues

Pandora: Single unit fully coherent S and X band software defined radar

A photonic-based coherent dual band radar system demonstrator, tested in an operative aerial scenario, is presented. Photonic technologies have been used for simultaneous generation and detection of radar signals in the S- and X-band. The sharing of a single transceiver for both the frequency bands allows for a perfect coherence among the generated waveforms