A neural network approach to pulse radar detection

A multilayer feedforward neural network is applied to pulse compression. The 13-element Barker code and the maximum-length sequences (m-sequences) with lengths 15, 31, and 63 b were used as the signal codes, and four networks were implemented, respectively. In each of these networks, the number of input units was the same as the signal length while the number of hidden units was three and the number of output units was one. In training each of these networks, backpropagation learning was used and the number of training epochs was 500. Using this approach, a more than 40 dB output peak signal-to-sidelobe ratio can be achieved. These fault-tolerant neural networks can provide a robust means for pulse radar detection     

Multimode adaptive signal processing: a new approach to GMTI radar

We show how a single reflector antenna with a multimode feed horn can be used in a ground moving target indication (GMTI) radar. In particular, we demonstrate the simultaneous detection and estimation of angular location of a ground moving target via adaptive cancellation of ground clutter     

Receiver antenna scan rate requirements needed to implement pulsechasing in a bistatic radar receiver

Pulse chasing is a technique implemented by a bistatic or multistatic radar system that allows rapid and efficient search of a desired volume of space whereby the receiving antenna is made to follow or “chase” the transmitted pulse as it travels radially outward from the transmitter antenna. An expression for receiver antenna scan rate requirements is derived that corrects an error in the prior literature. The results give significantly reduced scan rates in the forward scatter region near the baseline showing that pulse chasing is more easily implemented using conventional analog beamformer phased array technology than was suggested by prior work     

A modular approach to digital networks for fourth-generationavionics

To support the Joint Advanced Strike Technology (JAST) baseline architecture, advanced avionic systems will need to be modular in nature and support open commercial standards. System issues affecting these modules are discussed and the performance of existing and planned demonstration hardware is described     

Noncoherent approach to through-the-wall radar localization

A noncoherent through-the-wall radar system approach, based on stepped-frequency signal synthesis and trilateration technique, is presented. This approach involves multiple independent monostatic radar units and as such, provides flexibility in positioning the units with various standoff distances and inter-element spacing. The performance of the proposed noncoherent localization system was demonstrated using simulated and real data. The results show that the radar is able to detect and locate multiple targets behind walls     

A flexible processor for a digital adaptive array radar

A digital beamforming processor for an adaptive array radar is described. The functionality and the architecture of the processor are strongly driven by a goal of achieving adaptive null depths in the 60-dB to 70-dB range, which necessitates substantial preprocessing of each channel. In particular, conversion to baseband quadrature channels is accomplished digitally using a single A/D converter per channel, and FIR (finite impulse response) equalizing filters are employed in each channel to match channel transfer functions. The processor is highly modular, and this not only distributes the total processing load, but also the I/O (input/output) bandwidth requirement. This is accomplished by distributing the adaptive beamforming algorithm systolically across a linear array of processing nodes. The processor is expandable to a different number of channels and sufficiently flexible to be applied to other problems of an array signal processing nature. Experimental data presented demonstrate that the processor is capable of supporting channel-to-channel cancellation of interfering signals to the level of -65 dB     

A new approach to automatic target recognition

The fundamental problems of automatic target recognition (ATR) are discussed. A new approach to ATR is suggested that includes: a new method of scoring ATR performance, a new concept of artificial images, a new method called probing for extracting target signature knowledge from image experts, and suggestions for coping with the problem of insufficient test data and algorithm obsolescence     

Bayesian gamma mixture model approach to radar target recognition

This paper develops a Bayesian gamma mixture model approach to automatic target recognition (ATR). The specific problem considered is the classification of radar range profiles (RRPs) of military ships. However, the approach developed is relevant to the generic discrimination problem. We model the radar returns (data measurements) from each target as a gamma mixture distribution. Several different motivations for the use of mixture models are put forward, with gamma components being chosen through a physical consideration of radar returns. Bayesian formalism is adopted and we obtain posterior distributions for the parameters of our mixture models. The distributions obtained are too complicated for direct analytical use in a classifier, so Markov chain Monte Carlo (MCMC) techniques are used to provide samples from the distributions. The classification results on the ship data compare favorably with those obtained from two previously published techniques, namely a self-organizing map and a maximum likelihood gamma mixture model classifier.     

Comments on "Receiver antenna scan rate requirements needed to implement pulse chasing in a bistatic radar receiver"

For original paper see D.S.Purdy, ibid., vol.37, no.1, pp.285-7 (2001). It is shown that by selecting a different time variable, the approximations the author claims to be in error are indeed accurate. A reply by D.S.Purdy to these comments is included.     

A new approach to on-board stationkeeping of GEO-satellites

This paper proposes a new autonomous stationkeeping system suitable for geostationary satellite operation and presents the results of the computer simulations conducted to verify the proposed system. The proposed on-board stationkeeping system receives pseudo-range signal from the ground equipments located at two different positions with a long baseline, determines the orbit error in real-time, and generates the orbit control command. To minimize the complexity of the on-board stationkeeping logic and to improve reliability, a simple orbit controller has been designed, which generates a series of control signal making the orbit roughly follow the predetermined reference range data. The reference range data are assumed to be generated through a ground based computer simulation and embedded or uploaded with time tag. Finally, the performance of the proposed system has been verified through computer simulations.     

A new CFAR sidelobe canceler algorithm for radar

Signal or target detection is sometimes complicated by the presence of strong interference. When this interference occurs mainly in the sidelobes of the antenna pattern, a solution to this problem is realized through a sidelobe canceler (SLC) implementation. Since the false-alarm probability is a system parameter of special importance in radar, an interference-canceling technique for radar application should maintain the false-alarm probability constant over a wide range of incident interference power. With the requirements of sidelobe interference cancellation and constant false alarm rate (CFAR), a new algorithm for radar detection in the presence of sidelobe interference is developed from the generalized likelihood ratio test of Neyman-Pearson. In this development, the received interference is modeled as a nonstationary but slowly varying Gaussian random process. Cancellation of the sidelobe interference is based upon a `synchronous' estimate of the spatial covariance of the interference for the range gate being tested. This algorithm provides a fixed false-alarm rate and a fixed threshold which depend only upon the parameters of the algorithm     

A new approach to robust fault detection and identification

A methodology for instrument fault detection and identification (FDI) in linear dynamical systems subject to plant parameter variations or uncertainties is presented. At the heart of this approach is a robust estimator for which the necessary and sufficient conditions to its existence are outlined. The robust estimator can simultaneously estimate the unmeasurable state variables of the system for the purpose of control and provide necessary information for FDI purposes. A novel feature of this approach is that it can actually identify the shape and magnitude of the failures. The scheme allows for fast and accurate FDI, and can account for structural uncertainties and variations in the parameters of the dynamical model of the system. The overall fault tolerant control system strategy proposed is verified through simulation studies performed on the control of a vertical takeoff and landing (VTOL) aircraft in the vertical plane     

A new look at nonseparable synthetic aperture radar processing

The author examines the nonseparable, template correlation approach to digital-strip-mode synthetic-aperture radar (SAR) phase history processing and concludes that it can now outperform the traditional separable approaches in the areas of speed, image quality, control simplicity, and flexibility. A working nonseparable frequency-domain SAR processor is described and evaluated. The image quality is seen to be superior to that resulting from the separable approaches. Based on the working intermediate hardware implementation, the author strongly suggests that future VHSIC and other advanced implementation will provide extremely fast (real time), high-quality, small, flexible SAR processors     

A novel target detection approach based on adaptive radar waveform design

To resolve problems of complicated clutter, fast-varying scenes, and low signal-clutterratio (SCR) in application of target detection on sea for space-based radar (SBR), a target detection approach based on adaptive waveform design is proposed in this paper. Firstly, complicated sea clutter is modeled as compound Gaussian process, and a target is modeled as some scatterers with Gaussian reflectivity. Secondly, every dwell duration of radar is divided into several sub-dwells. Regular linear frequency modulated pulses are transmitted at Sub-dwell 1, and the received signal at this sub-dwell is used to estimate clutter covariance matrices and pre-detection. Estimated matrices are updated at every following sub-dwell by multiple particle filtering to cope with fast-varying clutter scenes of SBR. Furthermore, waveform of every following sub-dwell is designed adaptively according to mean square optimization technique. Finally, principal component analysis and generalized likelihood ratio test is used for mitigation of colored interference and property of constant false alarm rate, respectively. Simulation results show that, considering configuration of SBR and condition of complicated clutter, 9 dB is reduced for SCR which reliable detection requires by this target detection approach. Therefore, the work in this paper can markedly improve radar detection performance for weak targets.     

Advances in bistatic radar (Willis, N.J. and Griffiths, H.D., Eds.; 2007) [Book Review]

The editors have collected a comprehensive set of monographs that provide insight into the more recent history of bistatic radar design and implementation. This volume combines improved details of the environment along with novel system applications. Each chapter is authored by radar experts who had the vision and motivation to tackle a daunting development problem, and share their view of the successes and remaining implementation challenges. The book is divided into two parts: Bistatic/Multistatic Systems and Bistatic Clutter and Signal Processing. The book is an essential addition to the modern radar engineer's library.     

一种新的数字资源使用控制方法

分析典型数字版权管理框架中资源使用权限管理和权限转让存在的问题,提出一种新的数字资源使用控制方案.新方案给出了数字资源发放和使用中许可证书的产生、更新和防复制方法,简化了授权过程,加强了数字资源使用权限管理,保证了权限转让的安全性和可控性.     

New approach to a multistatic passive radar sensor for air/spacedefense

A method to apply the latest technology in Global Navigation Satellite Systems (GNSS), in particular the U.S. NAVSTAR GPS (NAVigation System for Timing And Ranging Global Positioning System) and the Russian GLONASS (GLObal'naya Nqvigatsionnaya Sputnikovaya Sistema), as a silent multistatic or parasitic radar for air defense is described. These satellite systems serving as navigational aids are well suited for low power radar applications due to the similarity and compatibility of the transmitted satellite signals with modern radar signals, such as spread spectrum modulation and Pseudo Random Noise (PRN) codes. Preliminary flight tests with airships, jet and propeller aircraft, helicopter, anti tank missiles and spaceborne targets (MIR) to study effects have been conducted     

A robust exponential mixture detector applied to radar

Exponential mixture probability density functions (pdfs) are shown to be useful models of radar sea clutter. The variability of certain parameters leads to estimation error and degradation in the performance of detection algorithms derived from this model. Robust implementations are introduced by assuming that parameters are known within certain intervals and selecting values to prevent an excessive number of false alarms. An empirical study demonstrates an average 6-9 dB gain in comparison with a constant false-alarm rate (CFAR) processor     

A new quadrature sampling and processing approach

A quadrature sampling and array signal processing technique that differs from earlier approaches in that is processes the data before the Hilbert transformation is presented. A fast Fourier transformation (FFT) technique that performs the discrete Fourier transformation (DFT) on the sampled data directly without Hilbert transformation is proposed for frequency-domain signal processing. For array signal processing, the proposed approach does not perform Hilbert transformation prior to signal combining. It features high processing speed, low distortion, and hardware simplicity. Error analyses, performance evaluation, and computer simulation results are included