Showing papers on "Moving target indication published in 1995"

Reconnaissance with ultra wideband UHF synthetic aperture radar

Abstract: The author addresses the problem of detecting and identifying stationary and moving targets with foliage penetrating UHF synthetic aperture radar (SAR). The role of a target's coherent SAR signature, which varies with the radar's frequency and aspect angle, in forming the Fourier space of the SAR signal is analyzed. The resultant relationship is the basis of an algorithm which, after extracting (digital spotlighting) the target's coherent SAR signature in the reconstruction domain, could be used to differentiate man-made structures from foliage. Methods for blind-velocity moving target indication are discussed. The main tool of the work is a signal theory based analysis of SAR signal via Fourier transform. However, the theory is at most as good as the collected SAR data. >

Image-based detection and tracking system and processing method employing clutter measurements and signal-to-clutter ratios

Abstract: A method for measuring and quantifying clutter, and target detection and tracking systems that employs wavelet-based clutter quantification to generate a clutter number and a signal-to-clutter ratio derived therefrom to achieve improved target detection performance. The method processes video signals representative of an image scene containing a target and background clutter to provide for more accurate tracking of the target by a tracker(s). The method comprises processing the video signals to compute a wavelet clutter number, processing the video signals to compute a signal-to clutter ratio using the wavelet clutter number, and generating a pointer to a lookup table that sets parameters and selects the tracker that is to be used to track the target based upon the computed signal-to clutter ratio.

Cramer-Rao bounds for target angle and Doppler estimation with space-time adaptive processing radar

Abstract: Space-time adaptive processing (STAP) can substantially improve airborne radar performance in environments with interference (clutter and/or jamming). This paper considers target parameter estimation with the STAP radar. The maximum-likelihood estimator for target angle and Doppler is reviewed. Cramer-Rao bounds for target angle and Doppler estimation accuracy are derived for an arbitrary interference scenario. These bounds show that in clutter, angle accuracy depends on the target Doppler and vice-versa. They are useful for quantifying the best-case degradation in estimator accuracy due to interference, and for determining the fractions of the Doppler space and coverage sector over which a specified level of accuracy can be achieved.

Step frequency waveform design and processing for detection of moving targets in clutter

Abstract: Step frequency waveforms have been used in measurement radars in anechoic chambers for high resolution imaging of stationary or rotating targets in one or two dimensions. However in operational scenarios such as detection of moving targets, frequency step waveform spreads the target return and shifts the target range resulting in a loss of target magnitude, range accuracy and range resolution. This paper models target return, brings out the problems associated with step frequency waveform and then describes a method for detection of moving target in the presence of clutter. Also discussed are step frequency waveform design considerations.

Moving target detection in SAR imagery: experimental results

Abstract: The detection of moving targets in SAR imagery has long been recognised as being of considerable utility adding much to the value of the derived information. A major obstacle to the detection of moving targets, however, is the broadening of the clutter spectrum as a result of air or spacecraft motion. This restricts the region of clutter free spectral space in which moving targets may be detected and in some cases (for example space based radar) this region becomes negligible. One potential solution is to use more than one spatial channel of information and examples include the use of displaced phase centre antennas (DPCA) and space-time adaptive processing (STAP). We present an overview of the background theory to dual channel DPCA and demonstrate the potential for clutter cancellation under ideal conditions. We then present results from an experimental dual channel C-band SAR. This allows the detected moving target to be overlaid on the background SAR image and the actual clutter improvement obtained can be compared with that predicted.

Comparison of DPCA and STAP for space-based radar

Abstract: Researchers have developed and examined adaptive moving target indicator (MTI) techniques that are able to cope with significant clutter spectral spreading that occurs for a radar mounted on a moving platform. In particular, displaced phase centre antenna (DPCA) techniques and space-time adaptive processing (STAP) techniques have been applied to airborne and space-based radars (SBR). Much work has been applied to the airborne MTI (AMTI) problem, where the literature seems to favour the use of STAP techniques over DPCA. The paper focuses on the SBR problem and examines some of the key differences between the airborne and space-based environments. In addition, the presence of targets is discussed with respect to the effect they have on target improvement factor. These discussions suggest that DPCA, rather than STAP, may well provide the better cost/performance trade-off for SBR.

Target detection in post-STAP undernulled clutter

Abstract: We describe a new detection algorithm for use with adaptively beamformed radar data. It is designed to take advantage of the a priori knowledge of the location of the ground clutter azimuth-Doppler ridge. In real data, the clutter is likely to be non-homogeneous, leading to the possibility of undernulled clutter discretes appearing in the adaptive beamformer output, the magnitude and frequency of which depend directly on the choice of training set for the adaptive nulling algorithm. The new detection algorithm estimates the magnitude of such undernulled clutter, and adjusts its threshold to account for the amount of residual clutter appearing in the adaptive beam. The advantage of such a detector lies in reducing the number of false alarms due to clutter discretes while maintaining detector sensitivity in areas in which the clutter discretes are well-nulled by the adaptive nulling algorithm.

Method for the detection, localization and velocity determination of moving targets from raw radar data from a coherent, single- or multi-channel image system carried along in a vehicle

Abstract: In a method for the detection, localization and velocity determination of moving targets from raw radar data from a coherent, single- or multi-channel image system (SAR), for representing the surface of the earth with different backscatter ratios, chronologically successive azimuth spectra are continuously formed during a defined period of time and a frequency shift of the backscatter ratio portion is obtained by determining the position of the maximum of the correlations between respectively two azimuth spectra formed chronologically directly in succession. Then the frequency shifts of the entire raw radar data set are evaluated for producing a frequency shift map. By searching for values deviating from the nominal Doppler rate in the Doppler rate map, a respective moving target is detected and the center of an image of the detected moving target is formed from this. By neglecting its radial acceleration, the tangential velocity of the moving target is determined by means of a Doppler rate taken from the Doppler rate map, and finally the radial velocity of the moving target is determined from the ratio of a length of the moving target in the range direction on the Doppler rate map and the duration of a scanning time by the antenna.

Space-time clutter covariance matrix computation and interference subspace tracking

Abstract: A fast method of computing ideal space-time clutter covariance matrices is described and the method's application to the study of clutter interference subspaces is considered. These areas are of principal importance in the study of space-time adaptive processing (STAP) for airborne pulse Doppler radar arrays. Formulae for clutter covariance matrices assuming various stochastic models are first derived, then a fast algorithm is developed in the case of uncorrelated patch-to-patch clutter with arbitrary illumination and reflectance. Finally, the clutter interference subspace as a function of scan angle for the case of a rotating sensor array is studied.

Ultra-wideband/short-pulse radar for target identification and detection-laboratory study

Abstract: A laboratory study was conducted to investigate the schemes of radar target identification and detection using an ultra-wideband/short-pulse (UWB/SP) radar. In target identification, a correlation/wavelet transform scheme, a neural network technique and a time-domain imaging scheme were studied. To detect a target in a sea clutter environment, the E-pulse technique was utilized to minimize the sea clutter while enhancing the target response, thus facilitating its detection. It appears that a UWB/SP radar may provide higher resolution for target ID and more effective clutter suppression for target detection compared with conventional radars.

Detecting moving targets in SAR imagery by using a phase-error correction algorithm

Abstract: Motion of a target induces phase errors in a synthetic-aperture (SAR) signal (phase) history that cause the image of the moving target to be smeared in azimuth. We can detect the presence of a moving target by sensing the smearing, as follows. We divide the complex image of a scene that includes a moving target into a grid of patches, and apply a phase-error correction algorithm to each patch. We have used the shear averaging phase-error correction algorithm. Patches that have large phase errors are likely to contain the image of a moving target. We also compute the sharpness of the image in the patch before and after phase-error correction; an increase in sharpness indicates the presence of a moving target, and it is a better indicator than the magnitude of the phase error. This approach requires just a single-antenna conventional SAR system. It is highly sensitive to the azimuth component of target velocity and to radial acceleration.

Time-frequency analysis of radar target backscatter

Abstract: Studies of two orbiting spheres demonstrate the usefulness of time-frequency distributions for the analysis of radar signals. The spheres served as a simplified model for moving blades of an engine propeller or helicopter rotor. Illuminating the moving spheres with a continuous wave radar generated a backscatter signal which was difficult to interpret in either the time or the frequency domains. By applying the binomial distribution (a discrete time-frequency distribution) we could clearly associate each sphere with its corresponding doppler return. The binomial distribution provided a detailed view of the target dynamics, opening the way for target classification and identification. The structures and details available in the time- frequency domain were not readily exploited in the original signal representation.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Mti radar system

Abstract: PURPOSE:To provide an MTI (moving target indication) radar system in which the size of a coherent MTI pulse Doppler radar is reduced by preventing the circulation of signals. CONSTITUTION:Coherent MTI radar equipment generates transmitting signals by mixing oscillated signals outputted from a highly-stabilized oscillator 1 and local signals transmitted from a local signal generator 2 and IF frequency signals having the same frequency as the local signals have by mixing the reflected signals of the transmitting signals from a target and the oscillated signals from the oscillator 1 and extracts the movement information of the target by detecting the phase of signals obtained by converting the frequency of the IF frequency signals by using the receiving local signals from the local signal generator 2. The radar equipment is provided with a variable frequency divider 23 which divides the frequency of the oscillated signals outputted from the oscillator 21 at a variable dividing ratio so that the radar equipment can generate the transmitting and receiving local signals.

Integrated GPS/lNS/SAR/GMTI Radar Precision Targeting Flight Test Results

Abstract: This paper summarizes the results of a series of flight tests flown to evaluate the precision targeting performance improvements obtainable with a modem tactical coherent airborne radar when operating with an integrated Global Positioning System/Inertial Navigation System (GPS/INS). The radar used in these experiments was the AN/APG-76 which has both synthetic aperture radar and ground moving target indication (GMTI) modes. Performance was evaluated with two integrated GPS/INS systems, a Honeywell H-764G and a Litton LN-1 OOG both of which are state- of-the-art systems. Each system is implemented in a tightly coupled GPS/INS configuration with P/Y code GPS receivers. The testbed for these flight tests was a Gulfstream II aircraft that was instrumented to record all radar and GPS/INS data. Testing was done with both fixed and moving targets. The fixed target tests were performed using an array of surveyed comer reflectors; the moving target tests used a van moving along the edge of a runway. In both cases, the test results show that an order of magnitude improvement in targeting performance is obtained with use of GPS.

Radar signal processing device

Abstract: PURPOSE:To obtain a radar signal processing device for improving the detection rate of a target by effectively utilizing a filter where the number is limited in terms of the relationship with the number of bits. CONSTITUTION:An MTI map is set by an MTI (Moving Target Indicator) map generator 1, an automatic clutter map is set by an automatic clutter map generator 2, a trigger pulse for stagger synchronization is generated by a synchronizer 4, and a specific filter coefficient which is different for each trigger pulse is output from a filter coefficient controller 3. By this filter coefficient, the filter characteristics of filters 8-11 are switched over and by a selection switch 5 and a switch 7 the transfer path of an input video signal is switched over. By switching over the filter characteristics of the filters 8-11 for each trigger pulse, filter characteristics are set to be compensated each other and the maximum signal of each filter is detected by a maximum value detector 16 as an output video signal.

Adaptive clutter map detector with a band-selective velocity filter in the multimode radar signal processor using array processing technique

Abstract: A new clutter map detector is designed and implemented using an array signal processor (ASP)-high performance multi-DSP board used for the multimode radar signal processor (MRSP)-for regulating the false alarm due to the strong discrete clutter as well as detecting the slowly moving strong target over the clutter zone This allows the map parameters to be updated such as input velocity filter coefficients, scale factor, and weighting factor The band-selective clutter map is available by adapting input velocity filter depending on the various types of clutter and/or target environments This approach can give high target detectability through on-site adaptation

Doppler Compensation of Range Profiles And Moving Target Discrimination In FMCW Radar

Abstract: In our work summarized in this paper, the response equation of moving target stimulated by a high-frequency wide-band LFMCW is firstly established. Then the method of estimating the radial velocities of both clutter center and moving target is studied. Moving target can be discriminated by the time-integrated Doppler spectrum obtained from sampled data of multiple frequency sweep periods. Finally the approaches of Doppler compensation of range profile are studied. It is shown that Doppler compensation is essential for time integrating in each range resolution cell to enhance target. The compensated range profiles are more applicable for both detection and identification -3 of radar target INTRODUCTlON For ground target identification, wide-band wave form technology is used in missile-borne or airborne radar to reach high range resolmon(HRR). Under HRR circumstance, stationary or slow-moving target can be discriminated and identified by using geometrical shape and structure features of range profile.ln missile-bome or airbome application, the position and density of each scatter in target range profile are rapidly glinting due to high speed of the platform, which leads to insbbilty for both stationary and moving target Considering Doppler movement, the obtained range profiles for target identification and discrimination are not easily to be integrated for enhancement of detection performance and not adaptive to be rule-based model for target classification. In order to detect, discriminate and identify moving target in a strong moving clutter background, the processing of Doppler compensation and integration wrth range profiles is to be done. DOPPLER EFFECTS OF RANGE PROFILE Provided that the incident wave is a linear frequency modulated continuous wave(LFMCW), the parameterr of which is shown in Fig. 1, where t = nT, itn (0 5 t , 5 I",) (1 1 Let Y, denote the radial velocity of the m-th (m c [ l , M ] ) scattering center, then its time delay can be given by The demodulated signal after removing the phase item that can be neglected is M

Estimating target velocity from pulse echoes

Abstract: A transducer (10) emits an ultrasonic RF pulse. This pulse interacts with a reflector or scatterer from the moving target where a part of the wave is reflected. The ultrasonic RF pulses are generated in a transmitter (12). The output from the transducer is an electrical RF pulse signal which is applied to a receiver (14). The echo signals from the receiver are applied to a pre-processor (20) which includes moving target indicator rejection circuits thereby reducing clutter and noise in the signals. Separate samplers (26), (28) and (30)-(32) are used for each butterfly line. Each butterfly line corresponds to a distinct linear velocity. The criterion that a signal corresponding to the returns should be equal in amplitude at all points along the correct trajectory may be used for envelope and RF signals.

Radar signal processing device

Abstract: PURPOSE:To improve the speed response characteristics and in-clutter target- detecting ability of a radar signal processing device so as to effectively detect a target. CONSTITUTION:An MTI(moving target indicator) eraser 1 processes video signals from inputted I/Q coherent video signals Sa to video signals S2a, S2b,... against which ground clutters distributed near zero-Doppler are suppressed by inputting the video signals to MDFs (multi-Doppler filters) 2a, 2b,... having multiple kinds of frequency characteristics. A clutter detection circuit 3 outputs an area signal Sc detected by comparing the amplitude of ground clutters contained in normal video signals Sb with threshold levels internally set in steps to an MDF selection circuit 4. The circuit 4 selects the video signals from the MDF 2a in the weak- clutter area and the video signals Sob from the MSD 2b in a strong-clutter area and outputs the selected video signals. Thus the degree of suppression of clutters is limited as necessary.

Neural network based moving target indicator for radar applications

Abstract: Although techniques of radar signal processing, including the moving target indicator (MTI), have been vastly improved by the availability of digital computers in recent years, these methods are generally based on complex mathematical procedures which make the engineering and design of radar receivers rather costly and vulnerable to electronic faults. On the other hand, biological systems (e.g., insects, birds) have capabilities far beyond those of the conventional MTI processors. This paper provides some evidence that Doppler shifts can easily be extracted with neural networks even in situations where only a limited number of noisy pulses are available for processing. Furthermore, it is easier to shape the frequency response of the neural network-based MTI (NN-MTI) as desired without needing the complex process of pole placement, which is traditionally required in both digital and analog filter design procedures. The nonlinear processing capability of a neural network is utilized to efficiently combine the Doppler processing and integration performed by conventional MTI and its coprocessor (i.e., integrator). The MTI implementation with neural networks reduces the number of required independent pulses for Doppler shift extraction in the presence of clutter. There are several other conflicting requirements for the optimum MTI design where the algorithmic procedures may not be as efficient. Therefore, shaping the magnitude frequency response of MTI filters demands the flexibilities offered by neural networks.

The analysis of compatible system of AMTI and SAR

Abstract: Based on the analysis of Adaptive Moving Target Indication (AMTI) and the signal processing of Synthetic Aperture Radar(SAR), a complete compatible system of AMTI and SAR is put forward. The compatibility and effectiveness of this system is proved in theory. The results of simulation show that this system not only has good ability in stationary targets imaging but also has ability in detecting moving targets under the background of strong clutter.

Probability density function of image tails interference in the detection of moving objects: generalized Rice's representation

Abstract: Passive radio wave remote sensing of a moving object by multiple individual sensors has been studied. A time-varying matched (TVM) filter bank has been suggested for the target reconstruction and detection. The TVM filter tuned to the target velocity compensates the target motion, maximizes SNR, and enhances the target image. In contrast, mis-tuned TVM filters yield blurred target images. In the multi-target case overlapped blurred image tails may interfere with the target recognition process, and cause target detection false alarm. In this work we study the statistics of the interference due to the randomly overlapped target image tails. Inspired by S. O. Rice's early work on shot noise statistics, assuming a uniform-Poisson distribution of target velocity-position, we present the probability density function (PDF), a generalized representation of Rice's integral, of the image tail interference. We evaluate this generalized Rice's integral. In an example we present the numerical results of the integral for the intermediate target density case.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.