Automatic target recognition using enhanced resolution SAR data

Using advanced technology, a new automatic target recognition (ATR) system has been developed that provides significantly improved target recognition performance compared with ATR systems that use conventional synthetic aperture radar (SAR) image-processing techniques. This significant improvement in target recognition performance is achieved by using a new superresolution image-processing technique that enhances SAR image resolution (and image quality) prior to performing target recognition. A computationally efficient two-level implementation of a template-based classifier is used to perform target recognition. The improvement in target recognition performance achieved using superresolution image processing in this new ATR system is quantified     

Taylor expansion of the differential range for monostatic SAR

The polar format algorithm (PFA) for spotlight synthetic aperture radar (SAR) is based on a linear approximation for the differential range to a scatterer. We derive a second-order Taylor series approximation of the differential range. We provide a simple and concise derivation of both the far-field linear approximation of the differential range, which forms the basis of the PFA, and the corresponding approximation limits based on the second-order terms of the approximation.     

Coherent Doppler tomography-a technique for narrow band SAR

Some concerns regarding a technique of narrowband synthetic aperture radar (N-SAR) imaging called coherent Doppler tomography (CDT), which may be a good candidate for spaceborne applications, are addressed. Using a single-frequency signal, are addressed. Using a single-frequency signal, resolution of two tenths of a wavelength can be achieved in the point spread function if the radar platform circles the ground path to be imaged. However, the high sidelobe level of -8-dB in the point spread function results in an unacceptable dynamic range. To reduce the sidelobe level, two approaches are presented: coherent processing using multiple discrete frequencies and noncoherent subaperture processing. Simulation results demonstrate that the sidelobe level is substantially reduced by both methods. However, the resolution is degraded and the computational overhead is greatly increased for noncoherent subaperture processing. Also presented is a possible satellite geometry configuration that could utilize N-SAR processing to provide high-resolution global mapping capability     

A Raw Signal Simulator for Bistatic SAR

This article proposes a new efficient raw signal simulator for the bistatic synthetic aperture radar (SAR) based on 2D fast Fourier transform (FFT) to deal with cases of both ideal trajectory and trajectory deviation. It begins with analyzing the geometric configuration and the range history of the bistatic SAR in side-looking and squint modes of ideal trajectory as well as trajectory deviation. Then a detailed and mathematical study is conducted on the equivalence relation of bistatic-to-monostatic applications (BTMA) in the case of ideal trajectory and trajectory deviation. Also a set of formulas are derived for the equivalence relation between bistatic SAR and monostatic SAR on some reasonable assumptions. Therefore, the application of the simulation method based on the 2D FFT for the monostatic SAR can be extended to the case of bistatic SAR. Finally, the simulation results prove the validity of this method. By comparing the efficiency of the proposed method with that of the time domain method, it is shown that the former is a few orders of magnitude higher.     

A new fourth-order processing algorithm for spaceborne SAR

A new fourth-order signal aperture radar (SAR) processing algorithm has been developed for a general satellite-Earth relative motion. The two-dimensional exact transfer function (ETF) is calculated and range-variant phase corrections have been calculated in order to process many azimuth lines per block. The ETF together with the phase corrections has been called the fourth-order EETF (extended ETF). It is also shown that a fourth-order EETF is necessary to process high quality images from spaceborne SAR with long integration times with spatial resolution around 1 m. The algorithm is fast and is anticipated to have good phase preservation properties     

ISE: intelligent synthesis environment for future aerospace systems

The Intelligent Synthesis Environment (ISE) being developed by NASA, UVA, and JPL for significantly enhancing the rapid creation of innovative affordable products and missions is described. ISE uses a synergistic combination of leading-edge technologies, including high-performance computing, high-capacity communications and networking, virtual product development, knowledge-based engineering, computational intelligence, human-computer interaction, and product information management. The environment will link scientists, design teams, manufacturers, suppliers, and consultants who participate in the mission synthesis, as well as in the creation and operation of the aerospace system. It will radically advance the process by which complex science missions are synthesized, and high-tech engineering systems are designed, manufactured, and operated. The evolution of engineering design is described along with the shortcomings of current product development techniques. The need for ISE to create high-science payoff missions and aerospace systems at affordable costs is discussed. The five major components critical to ISE and some of their sub-elements are described: namely, human-ISE interaction; infrastructure for distributed collaboration; rapid synthesis and simulation tools; intelligent life-cycle system integration; and cultural change in the creative process. Related government and industry programs are outlined and future impact of ISE on complex missions and aerospace systems is discussed.     

新型机载双通道SAR-GMTI实时算法

提出了一种用于机载双通道SAR的GMTI新算法,将自适应插值算法与多普勒频域DPCA相结合,先分析了新算法的原理,然后以一个距离误差系数不为正整数,并且有加速度存在的载机模型进行仿真.给出了使用新算法后的仿真结果,证明了算法的合理性和可靠性.     

An exact expression for resolution cell area in special case ofbistatic radar systems

An exact expression for the bistatic resolution-cell area (A _B) is developed for the special case in which either the transmit or receive antenna has a broad azimuth beamwidth or is omnidirectional. Quantitative examples are presented to illustrate the variation of A_B with location. A comparison is made with the performance of a commonly used approximation formula     

Using LabVIEW to provide rapid prototyping environment for theteaching of avionics systems

This paper describes a simulation environment which has been used to teach the fundamental principles of Avionics Systems to students of Systems Engineering at Loughborough University of Technology. A versatile model of a Radar System is detailed as an example and its attributes from a teaching perspective are highlighted. The generic nature of the environment is also described, as is its position within the systems life cycle     

A novel visual attention method for target detection from SAR images

Synthetic Aperture Radar(SAR) imaging systems have been widely used in civil and military fields due to their all-weather and all-day abilities and various other advantages. However, due to image data exponentially increasing, there is a need for novel automatic target detection and recognition technologies. In recent years, the visual attention mechanism in the visual system has helped humans effectively deal with complex visual signals. In particular, biologically inspired top-down attention models have garnered much attention recently. This paper presents a visual attention model for SAR target detection, comprising a bottom-up stage and top-down process.In the bottom-up step, the Itti model is improved based on the difference between SAR and optical images. The top-down step fully utilizes prior information to further detect targets. Extensive detection experiments carried out on the benchmark Moving and Stationary Target Acquisition and Recognition(MSTAR) dataset show that, compared with typical visual models and other popular detection methods, our model has increased ability and robustness for SAR target detection, under a range of Signal to Clutter Ratio(SCR) conditions and scenes. In addition, results obtained using only the bottom-up stage are inferior to those of the proposed method, further demonstrating the effectiveness and rationality of a top-down strategy. In summary, our proposed visual attention method can be considered a potential benchmark resource for the SAR research community.     

An environment for the integration and test of the Space Stationdistributed avionics systems

An approach is described to supplying an environment for the integration and test of the Space Station distributed avionics systems. Background is included on the development of this concept including the lessons learned from Space Shuttle experience. The environment's relationship to the process flow of the Space-Station verification, from systems development to on-orbit verification, is presented. The uses of the environment's hardware implementation, called Data Management System (DMS) kits, are covered. It is explained how these DMS kits provide a development version of the Space-Station operational environment and how this environment allows system developers to verify their systems performance, fault detection, and recovery capability. Conclusions on how the use of the DMS kits, in support of this concept, will ensure adequate on-orbit test capability are included     

基于LFMCW的空空导弹弹载SAR子孔径成像方法

线性调频连续波(LFMCW)合成孔径雷达(SAR)具有体积小、功耗低、分辨率高的特点已成为当前轻小型导引头雷达技术研究的热点.本文在详细分析了线性调频连续波信号特点的基础上,针对毫米波雷达应用于空空弹精确制导的需求,对其在高速平台、前斜视条件下成像的应用,建立了精确的去调频连续波信号模型.提出了一种基于FMCW毫米波雷达的子孔径成像算法,并通过仿真实验,验证了模型与算法的正确性     

A non-local vectorial total variational model for multichannel SAR image speckle suppression

This paper aims at the multichannel synthetic aperture radar(SAR)image speckle reduction.This paper proposes a novel energy minimized regularization model for multichannel image denoising,which is an extension of the non-local total variational model for gray-scale image.It contains two terms,namely the vectorial data fidelity term and the non-local vectorial total variation term.The latter is constructed by high-dimensional non-local gradient that contains the structure information of the multichannel image.The existence and the uniqueness of the solution of the model are proved.A fixed point iterative algorithm is designed to acquire the solution of this model.The convergence property of this algorithm is proved as well.This model is applied to the multipolarimetric and multi-temporal RADARSAT-2 images despeckling.The result shows that this model performs better than the original vectorial total variational model on texture preserving.     

A new technique for decoding Loran-C radionavigation signals

A new approach to the extraction of navigation information from Loran-C radionavigation signals is described. A reduced-rate time-reversed sequence is derived from the RF signal and processed by a finite-impulse response (FIR) filter. It is shown that proper design of the FIR filter and proper control of the sampling point guarantee the rejection of skywave contamination, and achieve excellent rejection of continuous-wave interference (CWI). The process is computationally efficient     

A new system identification technique for harmonic decomposition

An extended and unifying system identification technique is presented for a class of systems that include all main signal models that arise in the harmonic decomposition problem. This technique unifies and extends the previously developed system identification techniques which are improvements on the Pisarenko harmonic decomposition (or, its spatial dual, MUSIC) as they arise in arrays of sensors. The advantages of the technique and some of its specializations include having no assumptions of stationarity on the stochastic processes involved. Another contribution of this technique is that it can also be used without any resort to probability theoretic concepts, thus bypassing the approximation of autocorrelations via time averages, yielding the system parameters exactly. This technique can be utilized to determine the dominant modes of vibrations of flexible structures as well. An analogy is established between arrays of sensors for target signal returns and those that can be used for vibrations in flexible structures. This enables the results developed for each one of these problems to be applied to the other     

A multi-aircraft conflict detection and resolution method for 4-dimensional trajectory-based operation

Conflict Detection and Resolution(CDR) is the key to ensure aviation safety based on Trajectory Prediction(TP). Uncertainties that affect aircraft motions cause difficulty in an accurate prediction of the trajectory, especially in the context of four-dimensional(4D) Trajectory-Based Operation(4DTBO), which brings the uncertainty of pilot intent. This study draws on the idea of time geography, and turns the research focus of CDR from TP to an analysis of the aircraft reachable space constrained by 4D waypoint constraints. The concepts of space–time reachability of aircraft and space–time potential conflict space are proposed. A novel pre-CDR scheme for multiple aircraft is established. A key advantage of the scheme is that the uncertainty of pilot intent is accounted for via a Space-Time Prism(STP) for aircraft. Conflict detection is performed by verifying whether the STPs of aircraft intersect or not, and conflict resolution is performed by planning a conflict-free space–time trajectory avoiding intersection. Numerical examples are presented to validate the efficiency of the proposed scheme.     

一种P2P环境下的信任值计算算法

P2P环境下的信任反映的是一个节点对另一个节点信誉以及能力的综合评价。现有的信任模型多采用算术平均的方法来综合计算信誉,易受到不公正评价行为的攻击。为此提出了一种基于信誉的信任值计算算法。该算法考虑了信誉的时间衰减特点,使用内容兴趣相似度衡量节点推荐的信誉,并将信誉与其它相关因素综合得出信任值。仿真实验及分析表明,采用本算法的信任管理模型能抵御恶意评价的攻击,相比已有的信任模型能更为准确地计算信誉值。     

A novel pulse TOA analysis technique for radar identification

A new processing technique is presented for identifying individual pulse trains in a buffer load of pulse time-of-arrival (TOA) data from radar warning receiver sets currently in use for electronic warfare (EW). The method is based on the numerical characteristics of the matrix of the differences of the TOA data points. In particular, for a uniform pulse repetition interval (PRI) emitter, this matrix is a symmetrical harmonic Toeplitz matrix the inverse of which has banded tridiagonal form. This form leads to an estimator for the PRI in terms of the trace of the inverted matrix