65 research outputs found
Wide-Angle Multistatic Synthetic Aperture Radar: Focused Image Formation and Aliasing Artifact Mitigation
Traditional monostatic Synthetic Aperture Radar (SAR) platforms force the user to choose between two image types: larger, low resolution images or smaller, high resolution images. Switching to a Wide-Angle Multistatic Synthetic Aperture Radar (WAM-SAR) approach allows formation of large high-resolution images. Unfortunately, WAM-SAR suffers from two significant implementation problems. First, wavefront curvature effects, non-linear flight paths, and warped ground planes lead to image defocusing with traditional SAR processing methods. A new 3-D monostatic/bistatic image formation routine solves the defocusing problem, correcting for all relevant wide-angle effects. Inverse SAR (ISAR) imagery from a Radar Cross Section (RCS) chamber validates this approach. The second implementation problem stems from the large Doppler spread in the wide-angle scene, leading to severe aliasing problems. This research effort develops a new anti-aliasing technique using randomized Stepped-Frequency (SF) waveforms to form Doppler filter nulls coinciding with aliasing artifact locations. Both simulation and laboratory results demonstrate effective performance, eliminating more than 99% of the aliased energy
Radar Imaging Based on IEEE 802.11ad Waveform in V2I Communications
Since most of vehicular radar systems are already exploiting millimeter-wave
(mmWave) spectra, it would become much more feasible to implement a joint radar
and communication system by extending communication frequencies into the mmWave
band. In this paper, an IEEE 802.11ad waveform-based radar imaging technique is
proposed for vehicular settings. A roadside unit (RSU) transmits the IEEE
802.11ad waveform to a vehicle for communications while the RSU also listens to
the echoes of transmitted waveform to perform inverse synthetic aperture radar
(ISAR) imaging. To obtain high-resolution images of the vehicle, the RSU needs
to accurately estimate round-trip delays, Doppler shifts, and velocity of
vehicle. The proposed ISAR imaging first estimates the round-trip delays using
a good correlation property of Golay complementary sequences in the IEEE
802.11ad preamble. The Doppler shifts are then obtained using least square
estimation from the echo signals and refined to compensate phase wrapping
caused by phase rotation. The velocity of vehicle is determined using an
equation of motion and the estimated Doppler shifts. Simulation results verify
that the proposed technique is able to form high-resolution ISAR images from
point scatterer models of realistic vehicular settings with different
viewpoints. The proposed ISAR imaging technique can be used for various
vehicular applications, e.g., traffic condition analyses or advanced collision
warning systems
Compressive sensing for interferometric inverse synthetic aperture radar applications
The applicability of interferometric inverse synthetic aperture radar (InISAR) techniques to images reconstructed via
compressive sensing (CS)-based algorithms is investigated. Specifically, the three-dimensional (3D) reconstruction algorithm is
applied after exploiting CS for data compression and image reconstruction. The InISAR signal model is derived and formalised
in a CS framework. A comparison between conventional CS reconstruction and global sparsity constrained reconstruction
techniques is performed for different compression rates and different signal-to-noise ratio conditions. Performances on the 2D
and 3D reconstructions are evaluated. Results obtained on real data acquired during the NATO-SET 196 trial are shown
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