399 research outputs found
Passive RF Tomography: Signal Processing and Experimental Validation
Radio frequency (RF) tomography is an imaging technique based upon a set of distributed transmitters and receivers surrounding the area under observation. This method requires prior knowledge of the transmitters\u27 and receivers\u27 locations. In some circumstances the transmitters may be uncooperative, while in other cases extrinsic emitters may be used as source of opportunity. In these scenarios, RF tomography should operate in a passive modality. A previous work postulated the principles and feasibility of passive RF tomography. This research further develops the underlying theory through concise and ad-hoc signal processing. Experimental verification and validation corroborate the effectiveness of passive RF tomography for object detection and imaging
Bistatic SAR along track interferometry with multiple fixed receivers
This paper presents an along-track interferometry (ATI)study for a bistatic or multiestatic SAR configuration with fixed ground receivers. This technique can be useful for sea current estimation or for any problem of Ground Motion Target Indicator (GMTI). The proximity of the ground receivers
to the scene allows to be very sensitivite to velocities with small baselines. This paper also proposes a multibaseline approach for ATI able to diferenciate among different velocity contributions in the same resolution cell. At the end of this paper, some results over real acquired bistatic data will be presented and discussed. The data have been acquired using the C-band SAR Bistatic Receiver for INterferometric
Applications (SABRINA) and ESA’s ENVISAT satellite, as a transmitter of opportunity.Peer ReviewedPostprint (published version
Cooperative Coherent Multistatic Imaging and Phase Synchronization in Networked Sensing
Coherent multistatic radio imaging represents a pivotal opportunity for
forthcoming wireless networks, which involves distributed nodes cooperating to
achieve accurate sensing resolution and robustness. This paper delves into
cooperative coherent imaging for vehicular radar networks. Herein, multiple
radar-equipped vehicles cooperate to improve collective sensing capabilities
and address the fundamental issue of distinguishing weak targets in close
proximity to strong ones, a critical challenge for vulnerable road users
protection. We prove the significant benefits of cooperative coherent imaging
in the considered automotive scenario in terms of both probability of correct
detection, evaluated considering several system parameters, as well as
resolution capabilities, showcased by a dedicated experimental campaign wherein
the collaboration between two vehicles enables the detection of the legs of a
pedestrian close to a parked car. Moreover, as \textit{coherent} processing of
several sensors' data requires very tight accuracy on clock synchronization and
sensor's positioning -- referred to as \textit{phase synchronization} -- (such
that to predict sensor-target distances up to a fraction of the carrier
wavelength), we present a general three-step cooperative multistatic phase
synchronization procedure, detailing the required information exchange among
vehicles in the specific automotive radar context and assessing its feasibility
and performance by hybrid Cram\'er-Rao bound.Comment: 13 page
Implementation and Performance of Factorized Backprojection on Low-cost Commercial-Off-The-Shelf Hardware
Traditional Synthetic Aperture Radar (SAR) systems are large, complex, and expensive platforms that require significant resources to operate. The size and cost of the platforms limits the potential uses of SAR to strategic level intelligence gathering or large budget research efforts. The purpose of this thesis is to implement the factorized backprojection SAR image processing algorithm in the C++ programming language and test the code\u27s performance on a low cost, low size, weight, and power (SWAP) computer: a Raspberry Pi Model B. For a comparison of performance, a baseline implementation of filtered backprojection is adapted to C++ from pre-existing MATLAB® code. The factorized backprojection algorithm shows a computational improvement factor of 2-3 compared to filtered backprojection. Execution on a single Raspberry Pi is too slow for real-time imaging. However, factorized backprojection is easily parallelized, and we include a discussion of parallel implementation across multiple Pis
Passive Multistatic Radar Imaging using an OFDM based Signal of Opportunity
This paper demonstrates a proof of concept in using an OFDM-based signal of opportunity for SAR imaging purposes within a passive, multistatic radar construct. Two signal processing methods have been proposed to create phase history data. The same methods are applied in both a simulated software model and an experimental data collection environment to produce simulated SAR images using the CBP imaging algorithm. The images generated from both the experimental and simulated data were observed to be consistent with each other and with expectations in terms of resolution. Coherent addition of the images results in improved image resolution due to the geometric and frequency diversity of the multistatic scenario compared to the individual bistatic pairs
Multistatic and Multiple Frequency Imaging Resolution Analysis-Application to GPS-Based Multistatic Radar
International audienceThis paper focuses on the computation of the generalized ambiguity function (GAF) of a multiple antennas multiple frequencies radar system (MAMF). This study provides some insights into the definition of resolution parameters of a MAMF radar system. It turns out that the range and azimuth resolutions are not the most suitable criteria to specify the MAMF radar resolution. Therefore a new set of resolution parameters is introduced like the resolution ellipse which expresses the resolution anywhere in the image plane or δ→max, (δ→min) which expresses the highest (lowest) bound of the spatial radar resolution. To point out the pertinence of our study, we illustrate it with a MAMF radar system built around GPS satellites. The effect of the radar system geometry on resolution is investigated. For several scenarios, the GAF and its numerical form, the point spread function (PSF), are computed and their results are compared
DISCUS - The Deep Interior Scanning CubeSat mission to a rubble pile near-Earth asteroid
We have performed an initial stage conceptual design study for the Deep
Interior Scanning CubeSat (DISCUS), a tandem 6U CubeSat carrying a bistatic
radar as main payload. DISCUS will be operated either as an independent mission
or accompanying a larger one. It is designed to determine the internal
macroporosity of a 260-600 m diameter Near Earth Asteroid (NEA) from a few
kilometers distance. The main goal will be to achieve a global penetration with
a low-frequency signal as well as to analyze the scattering strength for
various different penetration depths and measurement positions. Moreover, the
measurements will be inverted through a computed radar tomography (CRT)
approach. The scientific data provided by DISCUS would bring more knowledge of
the internal configuration of rubble pile asteroids and their collisional
evolution in the Solar System. It would also advance the design of future
asteroid deflection concepts. We aim at a single-unit (1U) radar design
equipped with a half-wavelength dipole antenna. The radar will utilize a
stepped-frequency modulation technique the baseline of which was developed for
ESA's technology projects GINGER and PIRA. The radar measurements will be used
for CRT and shape reconstruction. The CubeSat will also be equipped with an
optical camera system and laser altimeter to sup- port navigation and shape
reconstruction. We provide the details of the measurement methods to be applied
along with the requirements derived of the known characteristics of rubble pile
asteroids.Comment: Submitted to Advances in Space Researc
GNSS Reflectometry and Remote Sensing: New Objectives and Results
The Global Navigation Satellite System (GNSS) has been a very powerful and
important contributor to all scientific questions related to precise
positioning on Earth's surface, particularly as a mature technique in geodesy
and geosciences. With the development of GNSS as a satellite microwave (L-band)
technique, more and wider applications and new potentials are explored and
utilized. The versatile and available GNSS signals can image the Earth's
surface environments as a new, highly precise, continuous, all-weather and
near-real-time remote sensing tool. The refracted signals from GNSS Radio
Occultation satellites together with ground GNSS observations can provide the
high-resolution tropospheric water vapor, temperature and pressure, tropopause
parameters and ionospheric total electron content (TEC) and electron density
profile as well. The GNSS reflected signals from the ocean and land surface
could determine the ocean height, wind speed and wind direction of ocean
surface, soil moisture, ice and snow thickness. In this paper, GNSS remote
sensing applications in the atmosphere, oceans, land and hydrology are
presented as well as new objectives and results discussed.Comment: Advances in Space Research, 46(2), 111-117, 201
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