Information Diversity in Coherent MIMO Radars

In this paper, the concept of information diversity in both the space and frequency domains is investigated for multiple-input multiple-output (MIMO) radars with widely separated antennas. Compared to phased-antenna arrays and multistatic radars, they can exploit more degrees of freedom, allowing them to maximize the information content upon centralized data fusion, thus granting unprecedented target detection and localization capabilities.This analysis proceeds in parallel with the running progresses of microwave photonics (MWP), which could represent, in the near future, a new paradigm for the development of centralized MIMO radar architectures.Thus, understanding the implications of information diversity becomes essential to foretell the system effectiveness in detecting and resolving closely spaced targets, as well as in suppressing sidelobes which may lead to false alarms. Performance metrics are proposed and evaluated to characterize the effects that information diversity has on centralized MIMO radars with widely separated antennas. On the other hand, the proposed methodology could reveal precious for designing the optimum system configuration

Photonic generation of phase-modulated RF signals for pulse compression techniques in coherent radars

A novel and flexible photonics-based scheme is proposed for generating phase-coded RF pulses suitable for coherent radar systems with pulse compression techniques. After selecting two modes from a mode-locked laser (MLL), the technique exploits an optical in-phase/quadrature modulator driven by a low-sample rate and low-noise direct digital synthesizer to modulate the phase of only one mode. The two laser modes are then heterodyned in a photodiode, and the RF pulse is properly filtered out. The scheme is experimentally validated implementing a 4-bit Barker code and a linear chirp on radar pulses with a carrier frequency of about 25 GHz, starting from an MLL at about 10 GHz. The measures of phase noise, amplitude- and phase-transients, and autocorrelation functions confirm the effectiveness of the scheme in producing compressed radar pulses without affecting the phase stability of the optically generated high-frequency carriers. An increase in the radar resolution from 150 to 37.5 m is calculated. The proposed scheme is capable of flexibly generating software-defined phase-modulated RF pulses with high stability, even at very high carrier frequency, using only a single commercial device with potentials for wideband modulation. It can therefore allow a new generation of high-resolution coherent radars with reduced complexity and cost. © 1983-2012 IEEE

Phase coding of RF pulses in photonics-aided frequency-agile coherent radar systems

An innovative optical scheme to generate software-defined phase-modulated radio frequency (RF) pulses with carrier frequency agility from a mode-locked laser (MLL) is proposed. The technique exploits a direct digital synthesizer and a Mach-Zehnder modulator to apply an intermediate frequency modulation to the MLL's modes. The heterodyne detection of the optical signal allows the generation of amplitude- and phase-modulated RF carriers with very high phase stability, suitable for coherent radar applications. Further, a single MLL can be used to generate carriers simultaneously at different frequencies, enabling frequency hopping or multifunctional radars, with no need to increase the complexity of the transmitter. Results show chirped and Barker-coded pulses at around 10 or 40 GHz in a single setup, without any performance degradation while increasing the carrier frequency. The proposed technique allows the practical realization of compressed pulses for coherent radars over a wide carrier frequency range, allowing the development of software-defined radar systems with improved functionalities. © 1965-2012 IEEE

Assessment of COVID-19 pandemic impact on guaranteeing food security in local school catering

Background. The Italian National Institute of Statistics (ISTAT) highlights that in 2020 10% of the Italian population could not afford an adequate meal every 2 days. Families with several children were more affected, for these children school meals represented the only access to a healthy diet. The European Commission Farm to Fork Strategy, concerning the COVID-19 pandemic (CP), underlines the need to act to ensure access to a sufficient supply of affordable food for all. In the Province of Trieste (PT) over 90% of pupils eat in school canteens (12,000 meals per day). The aims of the project were to verify the impact of CP on the food security of public school canteens (PSC) and determine any Nutritional Critical Points (NCPs) - Corrective Actions (CAs) to guarantee healthy equity meals for all pupils. Methods. The content of Public food procurement and service polices for a healthy diet (PFP) published by the WHO and the Nutrient Analysis Critical Control Points (NACCP) process as indicated by the Ministry of Health were applied. In the first quarter of 2021, all food procurement contracts (n = 6) and all of the school kitchens (n = 45) of PT PSC were verified, the University of Trieste analysed the composition of fresh desserts administered in 7 consecutive weeks. Results. The NACCP process showed NCPs on the low quality of afternoon snacks and on the quantitative/qualitative fat profile of fresh desserts, with a content of 69 to 72% of saturated fat, of 5 to 7% of trans fat and of 8 to 12% oxidized fat as a “dual quality” food. CAs were activated to support all PT PSC in reformulating fresh desserts, as well as in aiding the assessment of the food procurement landscape, activating regular monitoring of compliance and designing procurements adherent to PFP. Conclusions. Project outcomes highlight the importance of taking action to continuously support PSC in order to ensure healthy and equitable food environments for all and to contribute to building a resilient food system. Key messages. Guarantee healthy equity school meals for all pupils by developing on going processes to address the pandemic challenge. Ensure technical assistance to school catering to overcome the impact of COVID–19

Via-Less Microstrip to Rectangular Waveguide Transition on InP

Indium-Phosphide (InP) is one of the most common materials used for realizing active devices working in the millimeter frequency range. The isotropic etching profile of InP substrates limits the realization of passive devices, thus requiring an expensive and lossy hybrid platform. This paper presents a via-less, cost-effective and efficient solution for InP substrate. By using the proposed planar solution, it is demonstrated that rectangular waveguides can be realized on InP by fabricating a bed of nails structure which acts as a reflecting boundary for an impinging millimeter wave. As a proof of concept, a transition from microstrip to rectangular waveguide structure is realized within H-band (220-320 GHz) with a return loss of -18dB over a bandwidth of 30 GHz

Phase noise mitigation in photonics-based radio frequency multiplication

Two photonics-based radio frequency multiplication schemes for the generation of high-frequency carriers with low phase noise are proposed and experimentally demonstrated. With respect to conventional frequency multiplication schemes, the first scheme induces a selective cancelation of phase noise at periodic frequency-offset values, whereas the second scheme provides a uniform 3-dB mitigation of phase noise. The two schemes are experimentally demonstrated for the generation of a 110-GHz carrier by sixfold multiplication of an 18.3-GHz carrier. In both cases, the experimental results confirm the phase noise reduction predicted by theory

UWB FastlyTunable 0.550 GHz RF Transmitter based on Integrated Photonics

Currently, due to the 6G revolution, applications ranging from communication to sensing are experiencing an increasing and urgent need of software-defined ultra-wideband (UWB) and tunable radio frequency (RF) apparatuses with low size, weight, and power consumption (SWaP). Unfortunately, the coexistence of ultra-wideband and software-defined operation, tunability and low SWaP represents a big issue in the current RF technologies. Recently, photonic techniques have been demonstrated to support achieving the desired features when applied in RF UWB transmitters, introducing extremely wide operation and instantaneous bandwidth, tunable filtering, tunable photonics-based microwave mixing with very high port-to-port isolation, and intrinsic immunity to electromagnetic interferences. Moreover, the recent advances in photonics integration also allow to obtain very compact devices. In this article, to the best of our knowledge, the first example of a complete tunable software-defined RF transmitter with low footprint (i.e. on photonic chip) is presented exceeding the state-of-the-art for the extremely large tunability range of 0.5-50 GHz without any parallelization of narrower-band components and with fast tuning (< 200 s). This first implementation represents a breakthrough in microwave photonics

Quantum Radar: State of the Art and Potential of a Newly-Born Remote Sensing Technology

Quantum technology has already been introduced in many fields, like information processing and communications, and it can potentially change our approach to remote sensing in the microwave and millimeter-wave domain, leading to systems known as Quantum Radars. This new generation of systems does not leverage directly on quantum entanglement, since the latter is too “fragile” to preserve in a noisy and lossy environment,as a radar scenario,but rather on thehigh level of coherence derived from quantum entanglement. Quantum Illuminationisaprocess that exploitsquantum coherence of non-classical states of lightfor remote sensing. It allows for the generation and reception of highly correlatedsignals in the form of optical ormicrowave photons. By correlating the received signal photons with photons entangled with the transmitted ones,it is possible toclearly distinguish, among all the received photons, the echoes from background noise and interferences, boosting to an unprecedented level the sensitivity of remote sensing. Therefore, in principle,it is possible to detect very lowcross-radar section objets, such as stealth targets. Nowadays, very few experiments on Quantum Radar transceivers have been reported. This work aims at summarizing the state of the art of Quantum Radar, introducing its basic working principles, though raising the possible issues of such a technology; secondly, it will point out the possibilitiesof photonics-assisted Quantum Radars, proposing photonics as the ideal field where quantum science and remote sensing can meet for an effective cross-fertilizatio

Modeling meander morphodynamics over self-formed heterogeneous floodplains

This work addresses the signatures embedded in the planform geometry of meandering rivers consequent to the formation of floodplain heterogeneities as the river bends migrate. Two geomorphic features are specifically considered: scroll bars produced by lateral accretion of point bars at convex banks and oxbow lake fills consequent to neck cutoffs. The sedimentary architecture of these geomorphic units depends on the type and amount of sediment, and controls bank erodibility as the river impinges on them, favoring or contrasting the river migration. The geometry of numerically generated planforms obtained for different scenarios of floodplain heterogeneity is compared to that of natural meandering paths. Half meander metrics and spatial distribution of channel curvatures are used to disclose the complexity embedded in meandering geometry. Fourier Analysis, Principal Component Analysis, Singular Spectrum Analysis and Multivariate Singular Spectrum Analysis are used to emphasize the subtle but crucial differences which may emerge between apparently similar configurations. A closer similarity between observed and simulated planforms is attained when fully coupling flow and sediment dynamics (fully-coupled models) and when considering self-formed heterogeneities that are less erodible than the surrounding floodplain