1,723,039 research outputs found
100 years of radar
No full textThis book offers fascinating insights into the key technical and scientific developments in the history of radar, from the first patent, taken out by Hülsmeyer in 1904, through to the present day. Landmark events are highlighted and fascinating insights provided into the exceptional people who made possible the progress in the field, including the scientists and technologists who worked independently and under strict secrecy in various countries across the world in the 1930s and the big businessmen who played an important role after World War II. The book encourages multiple levels of reading. The author is a leading radar researcher who is ideally placed to offer a technical/scientific perspective as well as a historical one. He has taken care to structure and write the book in such a way as to appeal to both non-specialists and experts. The book is not sponsored by any company or body, either formally or informally, and is therefore entirely unbiased. The text is enriched by approximately three hundred images, most of which are original and have been accessed by detailed searches in the archives
Final results of the OPERA experiment on ντ appearance and the OPERA legacy
Full text linkOPERA (Oscillation Project with Emulsion tRacking Apparatus) was a long-baseline experiment at the INFN Gran Sasso laboratory (LNGS) designed to search for νμ → ντ oscillations in appearance mode. It took data from 2008 to 2012 with the CNGS neutrino beam from CERN. In 2015, after the detection of five ντ candidates with a signal-to-background ratio of ∼ 10, the discovery of ντ appearance in the CNGS beam was announced with 5.1σ significance. After having reached the experiment main goal, the selection of ντ candidates has been extended by loosening the selection criteria and applying a multivariate approach for events identification, in order to improve the statistical uncertainty in the measurement of the oscillation parameters and of ντ properties. Future experiments that will take advantage of the improvements done by OPERA in the use of nuclear emulsions will also be described
Directional dark matter search with nuclear emulsion
Full text linkThe NEWSdm experiment, based on nuclear emulsions, is proposed to measure the direction of WIMP-induced nuclear recoils. We discuss the potentiality, both in terms of exclusion limits and potential discovery, of a directional experiment based on the use of a solid target made by newly developed nuclear emulsions and read-out systems reaching sub-micrometric resolution
High precision surveillance system by means of multilateration of secondary surveillance radar (SSR) signals
No full textA system able to locate and identify aircraft and vehicles based on the reception and processing, with novel means and methods, of signals emitted by the trasponder of the secondary surveillance radar, shortly SSR. The system has a number of fixed stations distributed in the area of interest, e.g. in the airport area; any signal (the well known SSR reply/squitter) transmitted by the on-board transponder is received by four or more stations and the measurement of three or more differences of times of arrival (TOA) permits the reconstruction of the position of the transponder in spite of the fact that the transmission time is unknown. Suitable algorithms based on optimal estimation enhance both the accuracy of TOA measurements and the accuracy of the reconstructed position. The effects of possible overlapping of signal in time are avoided or mitigated by multiple source separation techniques based on least squares algebraic processing
High Resolution Measurements and Characterization of Urban, Suburban and Country Clutter at X-Band and Related Radar Calibration
No full textAt Tor Vergata University we are working on measurements and phenomenological characterization of urban, suburban and country radar clutter at X-band (3 cm wavelength, range resolution 8 to 10 m, azimuth resolution @ 1 km about 23.5 m) and on the related radar calibration problems. Measurements are “high resolution” when compared to most surveillance radars, and the related applications are in the frame of clutter maps for cognitive radar, drones detection, radar ornithology, and more. After calibration, done using opportunity targets with known radar cross section and a clutter fence, we carry on an analysis and a comparison of land clutter, considering different weather conditions: dry and wet soil, as well as the rare event of snow. Using fixed opportunity targets, such as lamppost and/or a large cylindrical steel tanker, we describe the attenuation effects due to the natural clutter fence (in this case due to cane thicket near to the target position) and its mitigation when the natural fence is gradually removed. Finally, but importantly, we analyze the multipath phenomenon due to reflection/scattering on ground, and propose a procedure to estimate the multipath factor and to correct for it
Radar environment experimental analysis for optimal siting
No full textSite selection for a new surveillance radar for various purposes as the surveillance of the airports and of urban and suburban areas, includes the optimal choice for minimization of clutter due to land, vegetation and man-made infrastructures. In the frame of measurement and modelling of clutter echoes, this paper is aimed to contribute with a practical procedure using lightweight, cheap and small radar after its calibration. Real-world Radar Cross Section measurements in a typical suburban area are shown and analyzed. Buildings, streets, highways, car parking areas with different coatings, large and medium size lampposts, bare soil, soil with vegetation of various types, trees, all in a radius of a very few kilometres, makes the Tor Vergata area interesting as far as land clutter characterization is concerned, as a test-bed for optimal siting procedures
Computer simulation of weather radar signals
No full textComputer simulation is largely used in radar signal analysis. The present work treats the simulation of precipitation echoes in weather radar applications. Such simulated signals are very useful when different processing techniques have to be tested and compared. Modern weather radar has both Doppler and polarimetric capabilities; from the simulation point of view, this implies the generation of two pseudorandom sequences with an assigned autocorrelation function (ACF) and an assigned cross correlation. A new generator of pseudorandom sequences is proposed and compared with an old one. The results show that the novel technique represents correctly both the ACF and the cross correlation, even when a limited number of samples (e.g. 8 or 16 typical of Air Traffic Control applications) is considered. Finally, the computer time needed to generate one sequence is evaluated and compared for both generators
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