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Realization of a flexible technological demonstrator for hf sky-wave data links
No full textRadio frequency range between 3–30 MHz is called high frequency or shortwave
radio. For a long time, the high frequency band has been considered as the most important
means for communications over long distance. The advent of new technologies, such as satellite
and terrestrial communications, made the high frequency systems obsolete. Despite that, a new
interest for these systems is growing due to the need of having a relatively cheap and simple system
for data and voice exchange, which could be a real alternative to existing system in case of their
failure. This paper aims to present an effective and flexible HF digital transceiver demonstrator
based on the software defined radio paradigma. The purpose of this demonstrator is to maintain
the “essential” information among the authorities in case of the failure of both satellite and
Internet communications for critical scenarios (e.g., terroristic attacks, natural disasters)
Software-defined multiband array passive radar (SMARP) project: An overview
No full textThis paper presents the results of the Software-defined Multiband Array Passive Radar (SMARP) project. The objective of the project was to design and realize a multiband passive radar demonstrator based on a software-defined solution and oriented to coastal surveillance applications. This work has been conceived in the framework of the Italian National Plan for Military Research. The project overall duration was 36 months and it was composed by three phases. The system concept and the results of each phase are presented in this paper
HF-OTH Skywave Radar for Missile Detection
No full textIn this paper missile detection capabilities of an HF-OTH skywave will be analysed and assessed.
Specifically we focus on a challenging scenarios that is the detection of ballistic missiles in their boost
phase for early activation of defence systems. Missile Radar Cross Section (RCS) is calculated during
target flight taking into account of frequency and viewing angle. Detection capabilities are assessed in
terms of peak power estimation and discrimination in the range-Doppler domain
Polarimetrically Persistent Scatterer Based Automatic Target Recognition
No full textReliable automatic target recognition (ATR) systems based on inverse synthetic aperture radar (ISAR) images require a robust feature selection. An ATR system based on polarimetric ISAR images has been recently proposed that extracts bright scatterers and uses their polarimetric signatures to define classification features. Since bright scatterers could be the results of multiple scattering, the concept of polarimetrically persistent scatterers (PPSs) has been introduced in a recent work. PPS is usually associated with single scattering mechanism and, therefore, may prove to be more robust for classification purposes. In this paper, an ATR system is defined that makes use of PPS. Furthermore, a detailed analysis is carried out to emphasize the meaning of PPSs when used for ATR
A Contrast Based Algorithm For Synthetic Range Profile Motion Compensation
No full textIn stepped-frequency radar, target motions produce range-profile distortions. Range shift, signal-to-noise ratio loss, and symmetric spreading are produced by target radial velocity, whereas target radial acceleration is mainly responsible for asymmetric smearing. Acceleration-distortion effects are usually negligible when a high Pulse Repetition Frequency (PRF) is used, although this is not the case for low-PRF radars. In this paper, a new motion-compensation technique based on contrast optimization is proposed. The innovative contributions of this paper are as follows: (1) A theoretical analysis of the distortions produced by target motions on the reconstruction of synthetic aperture radar is provided; (2) the proposed technique compensates both phase terms, which are due to target radial velocity and acceleration; therefore, synthetic range profiles can be focused by processing low-PRF radar returns; (3) a new cost function for the synthetic range profiles (namely, contrast) is defined and used for motion compensation; (4) the proposed technique can be applied to any kind of stepped-frequency waveforms; and (5) an estimation error analysis is performed, first theoretically and then by means of both simulations and real data
Contrast optimisation based range profile autofocus for polarimetric stepped frequency radar
No full textOne of the main benefits brought by the use of fully polarimetric radars is the ability to identify scattering mecha- nisms, which are related to the target physical properties. One of the most critical problems in synthetic range-profile recon- struction is the distortion induced by the target motion. Radial target velocity and acceleration generate second- and third-order phase terms in the received signal, which produce range shift and point-spread-function smearing. The distortions induced by the target motion produce, as a consequence, a signal-to-noise ratio loss. Recently, a method based on contrast maximization has been proposed in order to compensate target radial motions using single-polarization data. In this paper, an extension of such an algorithm is proposed that exploits fully polarimetric data in order to improve the target radial motion compensation
Signal Spectral Modelling for Airborne Radar in Presence of Windshear Phenomena
No full textA number of significant airplane accidents have resulted from windshear encounters during takeoff or landing. In these situations the radar signal received may be affected by a strong ground clutter that may make the conventional windshear detection algorithms implemented on ground-based systems unusable. Typically, the solution to this problem is to employ a clutter rejection filter and then process the filter output to derive weather information. In this study, a parametric bimodal spectral model of the raw radar signal from an airborne Doppler weather radar is proposed. The bimodal shape of the model has been defined as a superposition of clutter and windshear. The model can be used to define a windshear detection algorithm that can also directly estimate the physical weather parameters by using the estimated model parameters without using a clutter rejection pre-filter. Owing to the impossibility of testing a windshear detection system in a realistic environment, a simulated windshear data base has been developed by National Aeronautics and Space Administration (NASA) and Federal Aviation Administration (FAA) during their windshear research programme. The purpose of this study is to define a parametric bimodal spectral model and demonstrate its validity on the NASA-FAA windshear certification data set
An Integrated Space-Based Passive System for Maritime Operational Traffic Surveillance
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An integrated solution for the improvement of maritime traffic safety is proposed in this paper. Satellite and terrestrial-based data sources are fused to achieve a common operational picture for situational awareness. In particular, the system is composed of: 1)passive radars making use of DVB-T, DAB, and satellite broadcast transmitters for off-shore and coastal surveillance; 2) COSMO-SkyMedsatellites for large scale traffic monitoring; 3) Galileo positioning system for search and rescue services. Local and national authorities are the main potential users of such an integrated service
Passive ISAR for harbor protection and surveillance
No full textThis chapter presents the application of the PB-ISAR (passive bistatic-ISAR) technique to data collected in a harbor area. The results show the effectiveness of PB-ISAR algorithm for the purposes of harbor protection and surveillance. In Chapter 5, the theory behind PB-ISAR imaging has been detailed. The PB-ISAR algorithm is based on two main concepts. The first concerns the bistatic ISAR theory. Owing to the fact that a passive radar is intrinsically bistatic, since the transmitter and the receiver are not co-located, the bistatic ISAR theory can be applied [4]
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