Adaptive UWB-OFDM Synthetic Aperture Radar (original) (raw)
Related papers
Applied Computational Electromagnetics Society Journal
A novel approach for jamming-resistant and high-resolution synthetic aperture radar (SAR) imaging technique is explored based on ultrawideband orthogonal frequency division multiplexing (UWB-OFDM) waveform. Suitable waveforms for both friendly and hostile environment are proposed based on various random sequences and tested for SAR imaging in presence of a digital radio frequency memory (DRFM) repeat jammer. Adaptivity factor is introduced to make the system consistent in both environments. Wide-band ambiguity function (WAF) has been derived and the effect of subcarrier composition in UWB-OFDM waveform as SAR signal is analyzed to avoid ambiguity in image reconstruction. Appropriate UWB-OFDM pulse shaping is introduced for SAR imaging in jamming scenarios and in hostile environments to solve the susceptibility of conventional linear frequency modulated (LFM) chirp signal, Gaussian pulses and any other constant pulse shape to avoid the possibility of false target introduced by jammer and to achieve secured imaging in jamming scenarios. The peak side-lobe performance is examined in terms of number of OFDM sub-carriers and sub-carrier orientation. Index Terms ─ Orthogonal frequency division multiplexing (OFDM), synthetic aperture radar (SAR), SAR jamming and anti-jamming, and ultra-wideband (UWB).
Investigations on OFDM Signal for Range Ambiguity Suppression in SAR Configuration
IEEE Transactions on Geoscience and Remote Sensing, 2014
This paper presents an opportunity to cancel range ambiguities in synthetic aperture radar (SAR) configuration. One of the limitations of SAR systems is the range ambiguity phenomenon that appears with long delayed echoes. The reflected signal corresponding to one pulse is detected when the radar has already transmitted the next pulse. Thus, this signal is considered as an echo from the next pulse. This paper investigates the opportunity of coding the transmitted pulses using an orthogonal frequency-division multiplexing pulse. The results show that coded-OFDM signals outperform conventional chirp signal and make it possible to relax constraints placed upon the pulse repetition frequency.
A Novel OFDM Chirp Waveform Scheme for Use of Multiple Transmitters in SAR
IEEE Geoscience and Remote Sensing Letters, 2013
In this letter, we present a new waveform technique for the use of multiple transmitters in synthetic aperture radar (SAR) data acquisition. This approach is based on the principle of the orthogonal-frequency-division-multiplexing technique. Unlike multiple subband approaches, the proposed scheme allows the generation of multiple orthogonal waveforms on common spectral support and thereby enables to exploit the full bandwidth for each waveform. This letter introduces the modulation and the demodulation processing in regard to typical spaceborne SAR receive signals. The proposed processing techniques are verified by a simulation for the case of pointlike targets. Index Terms-Digital beamforming (DBF), multiple-input multiple-output (MIMO) synthetic aperture radar (SAR), orthogonal frequency division multiplexing (OFDM), orthogonal waveform, SAR.
Detection of Moving Targets by Focusing in UWB SAR—Theory and Experimental Results
IEEE Transactions on Geoscience and Remote Sensing, 2010
Moving-target detection in ultrawideband (UWB) synthetic aperture radar (SAR) is associated with long integration time and must accommodate azimuth focusing for reliable detection. This paper presents the theory on detection of moving targets by focusing and experimental results on single-channel SAR data aimed at evaluating the detection performance. The results with respect to both simulated and real data show that the ability to detect moving targets increases significantly when applying the proposed detection technique. The improvement in signal-to-clutter noise ratio, which is a basic requisite for evaluating the performance, reaches approximately 20 dB, using only single-channel SAR data. This gain will be preserved for the case of multichannel SAR data. The reference system for this study is the airborne UWB low-frequency SAR Coherent All RAdio BAnd Sensing II. Index Terms-Coherent All RAdio BAnd Sensing (CARABAS)-II, detection, fast backprojection, fast factorized backprojection (FFBP), moving target, multichannel, single channel, synthetic aperture radar (SAR), ultrawideband (UWB), UWB chirp scaling (UCS). I. INTRODUCTION O VER the last decades, synthetic aperture radar (SAR) has attracted considerable interest as the number of applications in geoscience, remote sensing, surveillance, and reconnaissance increases. The ability to effectively collect data in severe conditions, such as rain, clouds, and/or darkness, is considered to be the main advantage of SAR systems as compared to other imaging sensors. Ultrawideband (UWB) SAR is understood as SAR systems utilizing either a large absolute bandwidth or a large fractional bandwidth signal and a wide antenna beamwidth. Examples of experimental UWB SAR systems are Coherent All RAdio BAnd Sensing (CARABAS)-II operating in the lower very high frequency (VHF) band from 20 to 90 MHz [1], LORA in the VHF and UHF bands from 200 to 800 MHz [2], P-3 with a bandwidth of 515 MHz in the VHF/UHF bands at 215-900 MHz [3], ground-based BoomSAR with a spectral response extending from 50 to
SAR imaging with a hand-held UWB radar system
2012
Synthetic aperture radar (SAR) systems are used extensively for imaging vast areas using electromagnetic radiation. Radar systems have the benefit of being able to image areas which optical light cannot pass through, which makes them suitable for surveillance and weather monitoring, or monitoring through difficult atmospheric conditions. This thesis investigates, based on simulation and real data, whether a hand-held radar utilizing gaussian monopulses can function as a synthetic aperture radar device, by employing standard SAR focusing and filtering algorithms. The implementation of SAR algorithms was verified by a simulation and processing program written in the C programming language, and includes a novel algorithm for simulating raw SAR data. The novel algorithm was verified by inspecting the pulse-compressed and Global Backprojection (GBP)-focused image and its two-dimensional spectrum, and compared and contrasted to images generated in standard fashion. Handheld radar measurem...
Sensors, 2008
Synthetic wideband waveforms (SWW) combine a stepped frequency CW waveform and a chirp signal waveform to achieve high range resolution without requiring a large bandwidth or the consequent very high sampling rate. If an efficient algorithm like the range-Doppler algorithm (RDA) is used to acquire the SAR images for synthetic wideband signals, errors occur due to approximations, so the images may not show the best possible result. This paper proposes a modified subpulse SAR processing algorithm for synthetic wideband signals which is based on RDA. An experiment with an automobilebased SAR system showed that the proposed algorithm is quite accurate with a considerable improvement in resolution and quality of the obtained SAR image.
Real-Time Implementation of UWB-OFDM SAR Imaging System Using Shared Memory Based FPGA
2014
─ This paper presents a novel technique for FPGA based implementation of highresolution SAR system using UWB-OFDM architecture. Greater computation time and larger memory requirement are the main difficulties in processing large amount of raw data in real-time SAR imaging. Significant part of the computation time is related to range and azmuth compression of raw SAR data which in turns heavily depends on computing FFT, IFFT and complex multiplication. A shared memory based FPGA model is developed using Xilinx block-set that provides real-time SAR imaging with higher accuracy and less computation time. The design procedures are straightforward and can be applied to practical SAR system for real-time imaging. The model is designed as hardware co-simulation using Xilinx system generator and implemented on Xilinx Virtex-6 ML605 FPGA. Index Terms ─ Field Programmable Gate Araay (FPGA), Orthogonal Frequency Division Multiplexing (OFDM), Synthetic Aperture Radar (SAR), Ultra-Wideband (UWB).
OFDM Based UWB Synthetic Aperture Through-wall Imaging Radar
2008 Third International Conference on Broadband Communications, Information Technology & Biomedical Applications, 2008
... 6). 4. Simulation and results On the basis of the simplistic model of specific targets described above and the IEEE.15.3a UWB channel model, we led under Matlab/Simulink, a performance evaluation of an OFDM based 3 GHz bandwidth UWB radar for through the wall imaging. ...
Anti-jamming techniques for multichannel SAR imaging
IEE Proceedings - Radar, Sonar and Navigation, 2006
An airborne broadband jammer present in the mainbeam of a synthetic aperture radar (SAR) can potentially destroy a large region of the SAR image. In addition to this, multipath reflections from the ground, known as hot-clutter or terrain scattered interference will add a non-stationary interference component to the image. The goal of interference suppression for SAR is to successfully suppress these interferences while not significantly effecting the image quality by blurring, reducing the resolution or raising the sidelobe level. The paper provides an analysis of the degradation from hot-clutter, the limited restoration that multichannel imaging and slow-time space time adaptive processing (STAP) can provide and how fast-time STAP can improve the final image quality.