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Radar Conference, 2001. Proceedings of the 2001 IEEE

Date 3-3 May 2001

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Displaying Results 1 - 25 of 85
  • Proceedings of the 2001 IEEE Radar Conference (Cat. No.01CH37200)

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    Freely Available from IEEE
  • Conference Author Index

    Page(s): 463 - 464
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    Freely Available from IEEE
  • Ambiguity analysis for pulse compression radar using Gold code sequences

    Page(s): 111 - 116
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    This paper presents analytic, simulation, and measured results of using Gold sequences for radar pulse compression coding. Gold-coded waveform performance is characterized using the ambiguity function diagram, synonymous with matched filtering performance. Results indicate Gold-coded waveforms offer significant improvement in radar clutter suppression, resolution, and unambiguous range properties View full abstract»

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  • A multi-step selection procedure for estimating the number of signal components

    Page(s): 129 - 134
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    This paper considers a multi-step selection procedure to estimate the multiplicity of the smallest eigenvalue of a covariance matrix. The unknown number of signals present in radar data can be formulated as the difference between the total number of components in the observed multivariate data vector and the multiplicity of the smallest eigenvalue. We propose a selection procedure R, to estimate the multiplicity of the smallest common eigenvalue, which is significantly smaller that the other eigenvalues. We derive the probability of correct estimation, P(CE|R), and the least favorable configuration (LFC) for our procedure. Under the LFC, the P(CE|R) attains its minimum value over the parameter space of all eigenvalues. Therefore, a minimum sample size can be determined from the probability of CE under LFC, P(CE|LFC), in order to implement our new procedure while meeting a guaranteed probability requirement. Numerical examples are presented in order to illustrate our proposed procedure View full abstract»

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  • Dual frequency measurements of ocean forward scatter with an ultrawideband radar

    Page(s): 376 - 381
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    This paper presents an experiment description, along with data examples, for ultrawideband radar measurements of low grazing angle forward scatter associated with a test target mounted above a wind-disturbed sea surface. The measurement radar used sub-nanosecond transmit pulses (0.15 ns and 0.25 ns 3 dB pulse widths) at center frequencies of 9 and 4 GHz to achieve resolutions finer than 3 cm in the range dimension. This resolution was sufficient to fully resolve direct and multipath (both single and double bounce) contributions to the signal reflecting from a tower-mounted retro reflector. The geometry produced a nominal 3 degree grazing angle for forward scatter. Dual frequency measurements for a wind-disturbed ocean surface highlight changes in the magnitude and the location of the scatter components with time View full abstract»

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  • Adaptive detection in dense target environments

    Page(s): 187 - 192
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    We consider the impact of target signals corrupting the covariance estimate when implementing STAP in ground moving target indication (GMTI) scenarios. Herein, we propose a model for seeding the radar data cube with target signals and calculate both asymptotic and finite training data detection losses. In general, both the location and strength of the corruptive target signals influence performance: under practical conditions, SINR loss can exceed 10 dB. Measured MCARM data confirms the presence of ample ground moving target signals in the radar field of regard under typical operating conditions. We conclude by briefly considering several mitigating strategies as well View full abstract»

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  • Preliminary interferometric images of moving targets obtained using a time-modulated ultra-wide band through-wall penetration radar

    Page(s): 64 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB) |  | HTML iconHTML  

    A time modulated ultra-wide band (TM-UWB) wall penetrating impulse radar currently being developed at Time Domain Corporation, Huntsville, AL, is used to generate two-dimensional (2D) interferometric images (II) of moving targets. The goal is to determine the location of moving people behind walls or non-metallic visually opaque boundaries in real time using such a handheld wall penetrating radar operating under FCC Part 15, Class B limits. Interferometric images of an adult male person walking and crawling on the floor are presented for different types of common walls in front of the radar View full abstract»

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  • Full spatial and polarimetric characterization of a UHF antenna for ultrawide SAR

    Page(s): 382 - 386
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    This paper describes the analysis performed on a developmental ultra-high-frequency (UHF) antenna intended to support ultrawide synthetic aperture radar (SAR) on a Global Hawk platform. Both full-scale and ¼-scale test articles were fabricated. The patterns of the ¼-scale articles were measured over a full 4π steradians. Full-scale articles were measured over reduced angular regions sufficient to validate scaling. All measurements were fully polarimetric View full abstract»

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  • Radar imaging of ground moving targets

    Page(s): 426 - 431
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB) |  | HTML iconHTML  

    We analyze the effect of target motion on synthetic aperture radar images and discuss how a multi-aperture radar can detect, focus and relocate moving targets in clutter. AN/APY-6 radar data is used for analyzing the radar imaging of ground moving targets. Some applications of the time-frequency transform to detect and focus moving targets are also discussed View full abstract»

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  • An adaptive algorithm for enhanced target detection for bistatic space-based radar

    Page(s): 70 - 74
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB) |  | HTML iconHTML  

    The use of space-based bistatic radar has many attractive features (particularly related to covert observation and survivability) over that of conventional monostatic systems. However (if detection performance is to approach the monostatic case) these advantages come at the price of inherently more complex hardware and processing algorithms. In particular, when considering a bistatic system that utilizes a space-based transmitter/ground-based receiver architecture, obtaining detection ranges of practical value is problematic without having unrealistic requirements for space-based transmitter ERP or ground-based receiver antenna size. A predetection signal processing scheme is postulated which adapts to the nature of the bistatic signal, thus allowing for longer coherent integration times and correspondingly larger signal processing gain View full abstract»

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  • Bistatic reflectivity measurements at X, Ku, Ka and W-band frequencies

    Page(s): 404 - 409
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    Data that realistically represents the phenomenology of bistatic reflectivity is essential to the design of radar systems intended to sense land based targets and low flying aircraft. A large database exists describing the response of X-band monostatic reflectivity, and limited data is available for X-band bistatic reflectivity. However, there is little data in the literature describing bistatic reflectivity at Ku-band or at millimeter wave bands. Radar designers often resort to either scaling, or using directly, the bistatic reflectivity of X-band to model this environment at the other frequencies. A need exists to further characterize clutter phenomenology in order to design and project the performance of current and future systems. This paper provides an overview of X, Ku, Ka and W-Band bistatic measurements made at the Research Development and Engineering Center at Redstone Arsenal. The data collection includes both on-axis (zero degrees) and off-axis (10 and 30 degrees) measurements of the bistatic reflectivity response. The radar instrumentation design for the data collection is briefly described. A summary of the reflectivity results from smooth sand terrain is presented, along with preliminary modeling and statistical analysis. This work has application to tactical missile systems that must complete their engagements at low altitudes in a clutter environment View full abstract»

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  • Mitigation of digital array nonlinearities

    Page(s): 175 - 180
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    In a digital array, each receiver performs analog-to-digital-conversion (ADC), with the resulting digital data later combined via digital beamforming techniques. Since ADC is performed prior to beamforming, it is thus possible to enhance the dynamic range of each digital receiver through post-ADC array integration gain. Unfortunately, receiver correlation nonlinearities, such as spurious signals (spurs) or intermodulation distortion (intermods), across receivers can severely limit the achievable dynamic range enhancement. This paper proposes a methodology for mitigating the impact of receiver nonlinearities. In our approach the receiver input signals are carefully modified in a way that varies from channel to channel. The resulting signals are then processed by each digital receiver, introducing nonlinearities. Finally, the digital signals are corrected to restore the desired linear signal components. Examples are given of how this methodology can be applied to ADC, direct digital synthesizers (DDS), digital-to-analog converters (DAC), amplifiers, and mixers. In some cases, distortion is effectively reduced by a factor of N to N2, where N is the number of receivers View full abstract»

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  • On CFAR detection of oil slicks on the ocean surface by a multifrequency and/or multipolarization SAR

    Page(s): 351 - 356
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB) |  | HTML iconHTML  

    This paper addresses detection of oil spills on the sea surface as viewed by multifrequency and/or multipolarimetric synthetic aperture radars. We propose a two-stage processor: the first stage is a conventional detector designed to operate in a Gaussian environment; its detections are fed to a second stage designed to discriminate between candidate oil spills and templates of dark areas due to different phenomena, based upon different multifrequency and/or polarimetric signatures. Remarkably, the second stage possesses the constant false alarm rate property with respect to all of the unknown statistics of slick-free returns View full abstract»

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  • A novel threshold optimization for distributed OS-CFAR of multistatic radar systems by using the genetic algorithm

    Page(s): 275 - 278
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB) |  | HTML iconHTML  

    Distributed order statistics constant false alarm rate (OS-CFAR) detection techniques are important for nonstationary observation with varying weak narrowband random signals. However, it is very difficult to choose system parameters to obtain optimal threshold values because of the nonlinear property of the distributed OS-CFAR detection system. This paper provides a novel solution based on an effective and flexible genetic algorithm. Using this approach, all system parameters are directly coded in decimal chromosomes and they can be optimized simultaneously. The simulation results show that using the proposed approach one can achieve better performances than the reported methods and results. Furthermore, our method can also be used for more general nonhomogeneous situations with different fusion rules View full abstract»

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  • Texture modeling and validation using recorded high resolution sea clutter data

    Page(s): 387 - 392
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB) |  | HTML iconHTML  

    We consider modeling and estimating the texture in high-resolution non-Gaussian sea clutter. The cyclostationarity of sea clutter is investigated and validated by processing measured high-resolution data. The clutter is modeled as a compound Gaussian process and the texture as the superposition of real cosines with unknown frequencies, amplitudes, and phases. We propose a method for estimating the model parameters and retrieving the texture component from the intensity data in the presence of multiplicative noise (the speckle) with unknown power spectral density. The method exploits the clutter cyclostationarity and is based on a relaxation optimization approach. The ability of the proposed method to retrieve texture information is investigated by processing simulated and measured sea clutter data View full abstract»

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  • Filters for polarimetric calibration of UWB SAR imagery

    Page(s): 432 - 437
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    Polarimetric synthetic aperture radar (SAR) imagery is susceptible to degradation due to non-ideal responses in antennas and other hardware. Image corruption is especially serious in SAR operating over ultra-wide bandwidths (UWB) and imaging over wide angles, as the system response becomes a complicated function of angle and frequency. The usual approach to removing the system response from measured UWB SAR images involves operations in the two-dimensional spatial frequency domain of the imagery. We show that correction can also be performed by convolving the polarimetric images with two-dimensional polarimetric calibration filters (PCF). When compared to the frequency domain procedure, filtering offers improved calibration on extended-area targets, lower sidelobe noise, and computational savings. PCF can be synthesized from knowledge of the system response, or by an adaptive equalization technique that uses clutter returns to generate filters to correct for leakage, or crosstalk, between channels View full abstract»

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  • Shadow-feature-enhanced ML-CFAR detection for a Swerling 1 target in Weibull clutter

    Page(s): 444 - 447
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    This paper describes a shadow-feature-enhanced technique for the maximum-likelihood CFAR (ML-CFAR) detector, which is known to have a low CFAR loss. A general 15 dB signal-to-clutter ratio detection enhancement for a shadow length of 5 bins is obtained for a Swerling 1 target in Weibull clutter across a wide range of detection rates View full abstract»

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  • Superdirectivity and SNR constraints in wideband array-pattern design

    Page(s): 181 - 186
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    Wide instantaneous and tunable-bandwidth arrays pose a challenging design problem. Since the elements are usually spaced close to one-half wavelength at the highest frequency of operation, at lower frequencies the array may be considerably oversampled spatially. In a conventional time-delay-steered array the result is a beamwidth that is proportional to frequency. With a FIR filter at each element, however, superdirectivity can be achieved at lower frequencies, improving the beam characteristics. Constraints on efficiency, sensitivity, and SNR are derived to limit the undesirable effects of superdirectivity View full abstract»

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  • Selection of the radar waveform from tracking considerations

    Page(s): 246 - 251
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB) |  | HTML iconHTML  

    The conventional approach for tracking system design is to treat the sensor and tracking subsystems as completely independent units. However, the two subsystems can be designed jointly to improve system (tracking) performance. It is known that different radar signal waveforms result in very different resolution cell shapes (for example, a rectangle versus an eccentric parallelogram) in the range/range-rate space, and that there are corresponding differences in overall tracking performance. We develop a framework for the analysis of this performance. An imperfect detection process, false alarms, target dynamics and the matched filter sampling grid are all accounted for, using the Markov chain approach of Li and Bar-Shalom (1991). The role of the grid is stressed, and it is seen that the measurement-extraction process from contiguous radar “hits” is very important. A number of conclusions are given, perhaps the most interesting of which is the corroboration in the new measurement space of Fitzgerald's (1974) result for delay-only (i.e., range) measurements, that a linear FM upsweep offers very good tracking performance View full abstract»

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  • Space-time processing for airborne high range resolution phased array radar

    Page(s): 264 - 269
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    This paper considers the clutter suppression and feature extraction of multiple moving targets for airborne high range resolution (HRR) phased array radar. We show how to use a vector autoregressive (VAR) filtering technique to suppress the clutter for HRR radar data, then a relaxation-based multiple moving target to demonstrate the effectiveness of the algorithm View full abstract»

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  • MSAG based MAE-UAV active array antenna

    Page(s): 393 - 397
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    This paper summarizes the key enabling technologies developed during a three-year effort to design and demonstrate the advanced performance of a multi-function self-aligned gate (MSAG) MMIC-based MAE-UAV active array antenna. The antenna system was developed as prototype for future SATCOM and SAR antennas to be used aboard unmanned autonomous vehicles (UAV). This effort culminated in 1998 with a highly successful field demonstration at the CIRPAS facility (Center for Interdisciplinary Remotely Piloted Aircraft studies) in Marina, California View full abstract»

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  • Chaotic phase code for radar pulse compression

    Page(s): 279 - 283
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    This paper presents a novel binary phase coding scheme for radar pulse compression, which is derived from the logistic-map equation in the chaotic theory. The proposed logistic-map-based binary phase code (LMBPC) makes it feasible to achieve superior performance in detection range. The logistic-map equation in the chaotic theory is range resolution and Doppler tolerance simultaneously. The properties of LMBPC, including autocorrelation function, ambiguity diagram, performance under various noisy backgrounds, and the maximum Doppler tolerance, have been analyzed and compared to those of the conventional schemes, such as linear FM. The properties of LMBPC are very similar to those of the random binary codes. However, the generation of LMBPC is much simpler, and the available LMBPC is virtually infinite and not limited by the length of code. A parallel correlator structure for the pulse compression filter has also been introduced, which serves to improve the Doppler tolerance View full abstract»

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  • SAR prescreening using both target and shadow information

    Page(s): 147 - 152
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB) |  | HTML iconHTML  

    The utility of fusing shadow and intensity detections in a SAR prescreener is evaluated over the MSTAR database. We use either power ratio, GLRT or two-parameter CFAR tests to extract the two detections. For any testing strategy, the addition of shadow information improves performance View full abstract»

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  • Integration of Bayes detection and target tracking in real clutter image sequences

    Page(s): 234 - 238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB) |  | HTML iconHTML  

    We present an optimal Bayesian algorithm for integrated, multiframe detection and tracking of dim targets that move randomly in spatially correlated, cluttered image sequences. The algorithm consists of a multiframe minimum probability of error Bayes detector integrated with a multiframe maximum a posteriori (MAP) position estimator. The design of the detector/tracker incorporates the models for target signature, target motion, and clutter; it uses recursive spatio-temporal processing across all available frames to make detection decisions and to generate position estimates. A simulation with an artificial target template added to a real clutter background shows that the proposed algorithm outperforms the association of a standard single frame image correlator and a linearized Kalman-Bucy filter in a scenario of heavy clutter View full abstract»

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  • Development of a complete radar system model

    Page(s): 35 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB) |  | HTML iconHTML  

    This paper describes an approach to modelling synthetic aperture radar (SAR) and ground moving target identification (GMTI) modes that is applicable to both monostatic and bistatic operation. We describe an extensible method for modelling large complex radar systems that can be used to model platform and target motion, analogue and digital electronic components and complex signal processing algorithms. The key to this approach is a common data file format that allows the user to exchange simulated datasets for real flight trials data or combine the two without any recompilation of the modelling View full abstract»

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