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Showing papers on "Moving target indication published in 1998"


Proceedings ArticleDOI
TL;DR: In this article, the main features of airborne clutter are summarised and the potential of slow target detection before a Doppler coloured clutter background through space-time adaptive processing is demonstrated.
Abstract: Space-time adaptive processing (STAP) is an innovative tool for use with coherent phased array radar systems which is useful whenever the received signals (target and interference) are functions of both space and time. A prominent example is the clutter suppression in air and spaceborne MTI radar. In this tutorial paper the main features of airborne clutter are summarised. The platform motion causes clutter returns to be Doppler shifted so that the total of clutter arrivals exhibits a motion induced Doppler bandwidth. Airborne clutter is either characterised by the eigenspectra of the space-time covariance matrix or by the azimuth-Doppler spectra. These spectra demonstrate the potential of slow target detection before a Doppler coloured clutter background through space-time adaptive processing. Eigenspectra give an indication of the potential of subspace processing techniques which may lead to solutions for real-time on-board operation. Certain effects such as multiple-time-around clutter, clutter fluctuations, and system bandwidth, may degrade the detectability of slow targets.

242 citations


Proceedings ArticleDOI
TL;DR: In this paper, a variable structure interacting multiple model estimator for tracking groups of ground targets on constrained paths using moving target indicator reports obtained from an airborne sensor is presented, where the targets are moving along a highway, with varying inter- visibility due to changing terrain conditions.
Abstract: In this paper we present the development of a variable structure interacting multiple model estimator for tracking groups of ground targets on constrained paths using moving target indicator reports obtained from an airborne sensor. The targets are moving along a highway, with varying inter- visibility due to changing terrain conditions. In addition,the roads can branch, merge or cross. Some of the targets may also move in an open field. This constrained motion estimation problem is handled using an IMM estimator with varying mode sets depending on the topography. The number of models in the IMM estimator, their types and their parameters are modified adaptively, in real-time, based on the estimated position of the target and the corresponding road/visibility conditions. This topography-based variable structure mechanism eliminates the need for carrying all the possible models throughout the entire tracking period as in the standard IMM estimator, improving performance and reducing computational load.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

60 citations


Proceedings ArticleDOI
21 Mar 1998
TL;DR: In this paper, the authors present the development of a tracker based on the Interacting Multiple Model (IMM) estimation algorithm for tracking groups of ground targets using Moving Target Indicator (MTI) reports obtained from an airborne sensor.
Abstract: This paper presents the development of a tracker based on the Interacting Multiple Model (IMM) estimation algorithm for tracking groups of ground targets using Moving Target Indicator (MTI) reports obtained from an airborne sensor. The targets are moving along a constrained path, for example, a highway, with varying obscuration due to changing terrain conditions. In addition, the roads on which the targets travel can branch, merge, or cross. This constrained motion estimation problem is handled using an IMM estimator with varying mode sets depending on the topography. The design and implementation of the topography based Variable Structure IMM (VS-IMM) estimator is described. Simulation results are also presented.

36 citations


Proceedings ArticleDOI
12 May 1998
TL;DR: New subarray-subpulse schemes using forward and backward data vectors are introduced to overcome the data deficiency problem and it is shown that a multiplicative improvement in data samples can be obtained at the expense of negligible loss in space-time aperture of the steering vector.
Abstract: A major issue in space-time adaptive processing (STAP) for airborne moving target indicator (MTI) radar is the so-called sample support problem. Often, the available sample support for estimating the interference covariance matrix leads to severe rank deficiency, thereby precluding STAP beamforming based on the direct sample matrix inversion (SMI) method. The intrinsic interference subspace removal (ISR) technique, which is a computationally useful form of diagonally loaded SMI method, can handle this case, although the performance is poor in low sample situations. In this context, new subarray-subpulse schemes using forward and backward data vectors are introduced to overcome the data deficiency problem. It is shown that a multiplicative improvement in data samples can be obtained at the expense of negligible loss in space-time aperture of the steering vector.

33 citations


Journal ArticleDOI
TL;DR: In this article, a modified high order correlation (HOC) process and a track scoring mechanism were used to perform data association and track identification in the presence of heavy clutter, and the applicability of the method for continuous detection of target tracks that can originate and terminate at any scan is demonstrated.
Abstract: This work is concerned with the problem of multiple target track detection in heavy clutter. Using the "modified high order correlation" (HOC) process and a track scoring mechanism a new method is developed to perform data association and track identification in the presence of heavy clutter. Using this new scheme any number of very close, crossing or splitting target tracks can be resolved without increasing the computational complexity of the algorithm. The applicability of the method for continuous detection of target tracks that can originate and terminate at any scan is also demonstrated, In addition, the operating characteristics as a function of the clutter density are also provided. Simulation results on all the cases are presented.

31 citations


Proceedings ArticleDOI
01 Dec 1998
TL;DR: In this article, the theoretical performance analysis of a class of STAP detection algorithms under ideal and non-ideal conditions including target steering vector mismatch, sidelobe targets and inhomogeneities, and the impact two of the training strategies (i) sliding window with de-emphasis and (ii) power selected training.
Abstract: First generation airborne radar systems were non-adaptive, performing such operations as moving target indication (MTI), synthetic aperture radar (SAR) imaging, and displaced phased center array (DPCA) data processing. In most cases the processing was separate in space and time (Doppler). Optimal joint space-time adaptive processing (STAP) methods for target detection and parameter estimation have been known for years but were computationally infeasible. Promising hardware technologies, however, have encouraged a revisitation of these optimal methods. The efforts of the DARPA sponsored Mountaintop Program brought to the surface some of the weaknesses of these algorithms (which were derived and therefore only optimal under rather ideal assumptions rarely satisfied in the real world). We consider the theoretical performance analysis of a class of STAP detection algorithms under ideal and non-ideal conditions including target steering vector mismatch, sidelobe targets and inhomogeneities, and the impact two of the training strategies (i) sliding window with de-emphasis and (ii) power selected training. The detection algorithms considered include the classical adaptive matched filter (AMF), the generalized likelihood ratio test (GLRT), and the more contemporary adaptive cosine estimator (ACE), and the 2-D adaptive sidelobe blanker (ASB).

22 citations


Patent
19 Jun 1998
TL;DR: In this article, an MTI radar system is applied as an airport traffic control in which aircraft are detected as targets, and a lattice filter is used to process return signals to identify targets while substantially rejecting static and moving clutter.
Abstract: An MTI radar system transmits pulses with variable interpulse time periods and is structured with a lattice filter to process return signals to identify targets while substantially rejecting static and moving clutter. The MTI radar system also operates to reject adverse effects of transmitter instability in the processing of return signals. The MTI radar system is applied as an airport traffic control in which aircraft are detected as targets.

18 citations


Proceedings ArticleDOI
11 May 1998
TL;DR: In this article, the design and performance of GMTI radars for the general, non-SLAR case, where the array is oriented away from the side, the extreme case being a forward-looking airborne radar (FLAR).
Abstract: It is well known that detection of moving targets using an airborne radar is complicated by platform-induced spectral spreading of clutter returns. As a result, conventional pulse Doppler radars require a target to have a minimum detectable velocity (MDV) to be clear of mainbeam (and sidelobe) clutter. Extensive research into side-looking, multi-channel (i.e. multi-aperture) radars employing space-time adaptive processing (STAP) and displaced phase centre antenna (DPCA) processing techniques has been conducted, in order to reduce the requirement on MDV for airborne early warning (AEW) radar applications. GMTI (ground moving target indication) radars like JSTARS also employ similar techniques to detect slow ground moving targets such as tanks and jeeps. Most of the literature deals with side-looking airborne radars (SLAR), which is the case when the aperture phase centres lie along a line parallel to the flight path. This paper considers the design and performance of GMTI radars for the general, non-SLAR case, where the array is oriented away from the side, the extreme case being a forward-looking airborne radar (FLAR). A non-SLAR GMTI radar is attractive because it is applicable to mechanically rotated antenna arrays, often used for wide-angle surveillance; and, as a result, can be considered as an upgrade to existing surveillance radars.

17 citations


Proceedings ArticleDOI
TL;DR: In this article, the effects of platform manoeuvre on STAP clutter and jamming rejection performance for a forward-facing array (i.e., where the array is orientated transversally to the direction of travel) are examined.
Abstract: Space-time adaptive processing (STAP) techniques provide simultaneous rejection of jamming and clutter in airborne radar. The greatest benefits over conventional MTI (moving target indication) approaches are in terms of a capability to detect slow-moving targets which possess the same Doppler frequency as mainlobe clutter returns. This paper examines the effects of platform manoeuvre on STAP clutter and jamming rejection performance for a forward-facing array (i.e. where the array is orientated transversally to the direction of travel). It is shown that STAP slow-target detection performance is not sensitive to the radar platform orientation. It is also demonstrated that, under conditions of manoeuvre, STAP can provide better jammer rejection performance than architectures which cascade conventional clutter filtering and spatial adaptive beamforming.

15 citations


Journal ArticleDOI
TL;DR: In this article, the L-band radar backscatter from a small inland freshwater reservoir in central Massachusetts was used to investigate the effect of strong Bragg spikes in the clutter Doppler spectra from the reservoir at low (3 to 4 Hz) but non-zero doppler frequencies.
Abstract: Although radar surface-clutter reflectivities from terrain are generally much greater than those from water, strong Bragg resonances at low but non-zero Doppler frequencies in backscatter from small inland bodies of water might potentially cause false alarms for moving target indicator (MTI) or other Doppler signal-processing techniques designed for target detection in ground clutter. To provide data for investigating this concern, measurements of L-band radar backscatter were recorded from the surface of a small inland freshwater reservoir in central Massachusetts. These measurements were of unusually high system stability and spectral purity so as to provide up to 80 dB of available spectral dynamic range. Strong Bragg spikes occurred in the clutter Doppler spectra from the reservoir at low (3 to 4 Hz) but non-zero Doppler frequencies. This strong Bragg resonance was persistent in time and space throughout the measurements. Spectral results are presented for all four combinations of linear polarization. Comparison with tree clutter spectral results indicates that, when an occasional water body comes under surveillance at vertical polarization in otherwise generally forested terrain, water clutter spectral density is expected to exceed surrounding-terrain tree clutter spectral densities in the Bragg-offset Doppler vicinity by large amounts.

11 citations


Patent
27 Mar 1998
TL;DR: In this paper, a method and system for detecting moving objects using azimuth streaks in synthetic aperture radar (SAR) image data is presented. But the system is not suitable for the detection of moving objects.
Abstract: A method and system for detecting moving objects using azimuth streaks in synthetic aperture radar (SAR) image data are disclosed. The method and system of the present invention are directed to processing amplitude data relating to a SAR image, the first amplitude data having at least first and second indications corresponding to at least a first object moving at a substantially constant linear velocity and clutter, respectively, to separate or filter at least the first indication from the second indication, reducing/altering a spatial frequency power of the clutter corresponding to the second indication relative to a first azimuth streak power of a first azimuth streak corresponding to the first indication, and thresholding a first amplitude of the first azimuth streak to detect the first azimuth streak.

Proceedings ArticleDOI
11 May 1998
TL;DR: The secondary data for estimation of the clutter covariance matrix in space-time adaptive processing (STAP) is normally obtained from range rings in the vicinity of the test range ring, but this is not always true.
Abstract: The secondary data for estimation of the clutter covariance matrix in space-time adaptive processing (STAP) is normally obtained from range rings in the vicinity of the test range ring. The assumption is that near-by range rings are representative. However, this is not always true. A clutter model is developed and the condition necessary for obtaining a good estimate of the clutter covariance matrix are discussed. A theoretical basis for choosing reference rings which contain clutter patches that are equivalent to one or two patches within the test range ring is provided. A proposal for using a priori map data to classify clutter patches based upon the type of features contained within them is presented. It is conjectured that patches with equivalent classifications will have representative radar returns. An application to post Doppler radar processing is presented.

Proceedings ArticleDOI
11 May 1998
TL;DR: In this article, the Neyman-Pearson discrete-time detector for phase/amplitude coded radar signals in the presence of spatially-white distributed Rayleigh clutter is derived and a measure of the optimum detector's performance gain over that of a standard correlator is derived.
Abstract: This paper derives the Neyman-Pearson discrete-time detector for phase/amplitude coded radar signals in the presence of spatially-white distributed Rayleigh clutter. We consider processing of data records which are long relative to the pulse duration. A measure of the optimum detector's performance gain over that of a standard correlator is derived and calculated for several waveforms of practical interest. It is also shown that for the clutter-limited case that the detection performance in spatially-distributed Rayleigh clutter is virtually independent of waveform coding. This last result allows one to use this detector with a non-coded pulse radar and achieve similar detection performance to that of a pulse coded radar when all other parameters are held constant provided as the clutter dominates the noise.

Journal ArticleDOI
TL;DR: Curves for the detectability loss required thresholds, false alarm rate performance in clutter boundaries and detection performance in multiple target situations are presented with special emphasis on the important Swerling II target fluctuation model.

01 Jan 1998
TL;DR: In this paper, a Variable Structure Interacting Multiple Model (VS-IMM) estimator for tracking groups of ground targets on constrained paths using Moving Target Indicator (MTI) reports obtained from an airborne sensor is presented.
Abstract: In this paper we present the development of a Variable Structure Interacting Multiple Model (VS-IMM) estimator for tracking groups of ground targets on constrained paths using Moving Target Indicator (MTI) reports obtained from an airborne sensor. The targets are moving along a highway, with varying inter-visibility (obscuration) due to changing terrain conditions. In addition, the roads can branch, merge or cross. Some of the targets may also move in an open field. This constrained motion estimation problem is handled using an IMM estimator with varying mode sets depending on the topography. The number of models in the IMM estimator, their types and their parameters are modified adaptively, in real-time, based on the estimated position of the target and the corresponding road/visibility conditions. This topography-based variable structure mechanism eliminates the need for carrying all the possible models throughout the entire tracking period as in the standard IMM estimator, improving performance and reducing computational load.

Proceedings ArticleDOI
21 Mar 1998
TL;DR: Research was conducted to develop optimal orbital constellations for a representative space based radar (SBR) concept based on a representative phased array antenna design, enabling the sensor to look generally to the left and right of its flight path, but neither ahead nor behind.
Abstract: Research was conducted to develop optimal orbital constellations for a representative space based radar (SBR) concept. Many recent SBR designs are based on a multi-mode radar capable of a variety of missions such as airborne moving target indication (AMTI), ground moving target indication (GMTI), and synthetic aperture radar (SAR) imagery. This broad surveillance scope provides greater flexibility to the theater commander while providing and maintaining global access. The analysis was conducted on circular low earth orbits, at 926 km altitude, in order to avoid the Earth's radiation belts. Coverage computations were based solely on geometrical configurations and thus did not include processing effects such as weather, terrain features, or stealthy targets. Based on a representative phased array antenna design, the ground sensor pattern approximates a butterfly shape, enabling the sensor to look generally to the left and right of its flight path, but neither ahead nor behind. In addition, the radar is not able to see in a small area below itself. The unusual shape of the sensor footprint, combined with widely varying constraints for the separate missions, created challenging optimization problems. Coverage computations were conducted using both standard commercial software packages and custom software.

Proceedings ArticleDOI
TL;DR: The Moving Target Exploitation program is working to mitigate deficiencies by developing, integrating, and evaluating a suite of automated and semi-automated technologies to classify moving targets and units, and to provide indications of their activities.
Abstract: The understanding of maneuvering forces is invaluable to the warfighter, as it enhances understanding of enemy force structure and disposition, provides cues to potential enemy actions, and expedites targeting of time critical targets. Airborne ground moving target indicator (GMTI) radars are a class of highly-effective, all-weather, wide-area senors that aid in the surveillance of these moving ground vehicles. Unfortunately conventional GMTI radars are incapable of identifying individual vehicles, and techniques for exploiting information imbedded within GMTI radar reports are limited. The Defense Advanced Research Projects Agency (DARPA) Moving Target Exploitation (MTE) program is working to mitigate these deficiencies by developing, integrating, and evaluating a suite of automated and semi-automated technologies to classify moving targets and units, and to provide indications of their activities. These techniques include: aid in the interpretation of GMTI data to provide moving force structure analysis, automatic tracking of thousands of moving ground vehicles, 1-D target classification based upon high-range- resolution (HRR) radar profiles, and 2-D target classification based upon moving target imaging (MTIm) synthetic aperture radar (SAR). This paper shall present the MTE concept and motivation and provide an overview of results to date.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings ArticleDOI
F. Fukushima1, T. Fujisaka
31 Aug 1998
TL;DR: This paper proposes a new method, scanning PDI, which performs the PDI while compensating the Doppler shift which is caused by the target acceleration, and estimates the performance by deriving the relationship between thetarget acceleration and the detection probability of the target.
Abstract: In radar signal processing, PDI (post-detection integration) is widely used to improve the target detection performance). In the conventional PDI, it is assumed that the target is stationary and the Doppler frequency is constant. If the target is accelerated, the target detection performance degrades. To resolve the above problem, in this paper, we propose a new method, scanning PDI, which performs the PDI while compensating the Doppler shift which is caused by the target acceleration. Moreover, we estimate the performance of the scanning PDI by deriving the relationship between the target acceleration and the detection probability of the target.

Patent
31 Jul 1998
TL;DR: In this article, a moving target indicator (MTI) was proposed to detect a moving object at high accuracy by suppressing a Doppler frequency caused by clutter in a target information memory circuit.
Abstract: PROBLEM TO BE SOLVED: To provide a moving target indicator which can detects a moving target at high accuracy by suppressing a Doppler frequency caused by clutter. SOLUTION: The MTI(moving target indicator) 11 calculates a Doppler frequency fd and a speed standard deviation σ from digital I signal and Q signal subjected to MTI processing. Calculation results are recorded in a target information memory circuit 12 while being related to the antenna angle AZ at the time of reception and a distance RNG to a target. A target information processing circuit 10 reads out a Doppler frequency fd and a speed standard deviation σ corresponding to current antenna angle AZ and target distance RNG and averages the data thus read out and the Doppler frequency fd0 and speed standard deviation σ0 obtained from a pulse pair processing circuit 8. Based on the averaged results, a filter coefficient generating circuit 13 sets the filter coefficient of an MTI circuit 9 at such a value as the Doppler frequency caused by clutter is eliminated.

Journal ArticleDOI
TL;DR: In this article, a weight-magnitude-constrained adaptive moving target indicator (AMTI) is proposed, where only the phase of the filter weight is adjusted in real-time as a parameter in order to improve clutter suppression performance.
Abstract: An adaptive moving target indicator, AMTI, is a filter that automatically suppresses the moving clutter contained in a received radar signal. In AMTI based on an adaptive filter, the amplitude and the phase of the filter weight are simultaneously adjusted and this enhances the effect of the adaptation error. For this problem, this paper proposes weight-magnitude-constrained AMTI, where only the phase of the filter weight is adjusted in real-time as a parameter in order to improve clutter suppression performance. We then consider an environment in which the power of the desired signal is not negligible compared to the clutter power. In order to reduce the estimation error for the clutter center frequency, weight-magnitude-constrained AMTI introducing a median filter is proposed. The effectiveness of this approach is demonstrated by computer simulation. A situation is considered, where the received noise is modulated by a moving target indicator (MTI) that suppresses the static clutter in AMTI pre-processing; an algorithm for clutter center frequency estimation is presented for which the estimation accuracy is guaranteed. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(5): 41–50, 1998

Proceedings ArticleDOI
TL;DR: MITRE has developed a ModSAF-driven model for a UAV equipped with a moving target indicator (MTI) radar for wide-area surveillance, and a battlefield combat identification system for positive identification of friendly forces.
Abstract: The common ground station (CGS) receives data from the joint surveillance and target attack radar system aircraft and from other airborne platforms. High-resolution imagery such as that provided by an unmanned airborne vehicle (UAV) carrying an IR and/or synthetic aperture radar (SAR) sensor will be incorporated into an advanced imagery CGS operation. While this level of integration provides a wealth of valuable information, it also increase the complexity of planning, assessment and exploitation which in turn dictates flexible simulation tools for mission rehearsal and operator training. MITRE has developed a ModSAF-driven model for a UAV equipped with a moving target indicator (MTI) radar for wide-area surveillance, and a battlefield combat identification system for positive identification of friendly forces. The imaging functions are performed by integrating the UAV model with visualization software in order to render the sensor's view in real-time. This model forms the basis for a multisensor CGS simulation controls imaging task assignments which taken place when an MTI track is selected for imaging by means of a mouse click entry on an active MTI display. At that time, the UAV is commanded to fly an automatically determined trajectory in order to align MTI display. At that time, the UAV is commanded to fly an automatically determined trajectory in order to align itself for the imaging task. A beam footprint whose position, size and shape is determined by the sensor position, attitude, and field-of-view appears on the display as an indication of the relationship of the image display to the terrain in the operational scenario. A 3D visualization of the designated target area then takes place on a separate display.

Patent
27 Oct 1998
TL;DR: In this article, a radar video signal processing device for suppressing the remainder of cluttering without affecting the traveling target of an MTI (moving target indication) video signal that is outputted from a radar device by utilizing the cluttering characteristics.
Abstract: PROBLEM TO BE SOLVED: To provide a radar video signal processing device for suppressing the remainder of cluttering without affecting the traveling target of, for example, aircraft from an MTI(moving target indication) video signal that is outputted from a radar device by utilizing the cluttering characteristics. SOLUTION: A sweep-dividing means 1 divides a radar signal into sweep units (an assembly of signals from 0nM to the maximum detection distance being generated from one transmission pulse) and then outputs them. A scan integration means 3 gathers and integrates radar signals (MTI videos) in the same azimuth in sweep units for the number of scannings and outputs a scan integration signal. A differential means 4 subtracts the scan integration signal from the scan integration means 3 from the radar signal from the sweepdividing means 1, thus obtaining a differential signal where only the clutter extinction remainder constituent is eliminated while retaining the target signal constituent of traveling targets such as aircraft in the radar signal (MTI video).

Journal Article
TL;DR: In this paper, an optimal space-time moving target indication (MTI) processor for the airborne radar is proposed. The optimization is based on a stochastic target model, rather than deterministic target models adopted in most space-Time MTI processor designs.
Abstract: This paper presents an optimum space-time moving target indication (MTI) processor for the airborne radar. The optimization is based on a stochastic target model, rather than deterministic target models adopted in most space-time MTI processor designs. The optimum solution that maximize the improvement factor yielded by the processor is shown to be the generalized eigenvector corresponding to the smallest generalized eigenvalue of the signal and clutter covariance matrices. A suboptimal, but computationally simpler solution to this problem is also derived. This approach requires the solution of a linearly constrained minimum variance (LCMV) problem. Unlike typical LCMV problems, our solution also calculates the response vector specifying the frequency response along the look direction. Computer simulation results demonstrating the usefulness of our methods are included in the paper. The results indicate that the suboptimal solution does not suffer from significant performance loss.

Patent
28 Jan 1998
TL;DR: In this article, a target detection device uses a first target recognition system with a target camera and a second one with a directional beam transmitter, supplying a pulsed beam (80) to the target detection region and a cooperating receiver for the reflected beam (88).
Abstract: The target detection device uses a first target recognition system with a target camera and a second target recognition system (64) with a directional beam transmitter, supplying a pulsed beam (80) to the target detection region and a cooperating receiver for the reflected beam (88). The beam propagation time data is evaluated for imaging the target detection region.

Proceedings ArticleDOI
12 May 1998
TL;DR: The optimization is based on a stochastic target model, rather than deterministic target models adopted in most space-time MTI processor designs, and results indicate that the suboptimal solution does not suffer from significant performance loss.
Abstract: This paper presents an optimum space-time moving target indication (MTI) processor for the airborne radar. The optimization is based on a stochastic target model, rather than deterministic target models adopted in most space-time MTI processor designs. The optimum solution that maximizes the improvement factor yielded by the processor is shown to be the generalized eigenvector corresponding to the smallest generalized eigenvalue of the signal and clutter covariance matrices. A suboptimal, but computationally simpler solution to this problem is also derived. This approach requires the solution of a linearly constrained minimum variance (LCMV) problem. Unlike typical LCMV problems, our solution also calculates the response vector specifying the frequency response along the look direction. Experimental results demonstrating the usefulness of our methods are included in the paper. The results indicate that the suboptimal solution does not suffer from significant performance loss.

Proceedings ArticleDOI
11 May 1998
TL;DR: In this article, the removal of ground clutter from a Doppler shifted radar echo is examined from a non-traditional point of view that is particularly apt for an agile beam radar and digital signal processing.
Abstract: The removal of ground clutter from a Doppler shifted radar echo is examined from a non-traditional point of view that is particularly apt for an agile beam radar and digital signal processing. The observation in such a radar is, for each range sample, a finite duration sequence of complex envelope values. Thus, the observation is a complex vector. Clutter removal is the act of operating upon the observation vector to produce another vector that has its clutter component eliminated or substantially reduced. The operation is a matrix transformation that is, essentially, the inverse of the covariance matrix of the interference-noise plus clutter. The resulting vector is then applied to a bank of Doppler processes to produce: (a) test statistics for target detection; (b) spectral analysis to get the spectral moments of meteorological echo. The matrix processing approach removes the necessity for such things as initialization of the clutter filter. Spectral analysis is emphasized. The frequency response, clutter attenuation, and clutter improvement factor are defined in view of the matrix processing approach. In addition, the bias to be expected because of the clutter and its removal are analyzed and graphs are presented showing the bias to be expected for various spectral widths of clutter versus the frequency "notch" width of the matrix processor.

Patent
13 Aug 1998
TL;DR: In this paper, a method and system process amplitude data relating to a SAR image is presented, where first amplitude data has at least first and second indications corresponding to at least a first object moving at a substantially constant linear velocity and clutter.
Abstract: A method and system process amplitude data relating to a SAR image. First amplitude data has at least first and second indications corresponding to at least a first object moving at a substantially constant linear velocity and clutter, respectively. The first indication is separate or filtered from the second indication. A spatial frequency power of the clutter corresponding to the second indication is reduced/altered relative to a first azimuth streak power of a first azimuth streak corresponding to the first indication. A first amplitude of the first azimuth streak is thresholded to detect the first azimuth streak.