Total ionizing radiation effects of 2-T SONOS for 130 nm/4 Mb NOR flash memory technology

In this paper,we have studied the total ionizing dose(TID)radiation response up to 2 Mrad(Si)of silicon-oxide-nitride-oxide-silicon(SONOS)memory cells and memory circuits,fabricated in a 130 nm complimentary metal-oxide-semiconductor(CMOS)SONOS technology.We explored the threshold voltage(VT)degradation mechanism and found that the VT shifts of SONOS cells depend on the charge state;simply programming the cell to a higher VT cannot compensate for the radiation induced VT loss.The off-state current(Ioff)increase in the SONOS cell is also studied in this paper.Both VT and Ioffdegradation would affect the memory system.Read data failures are mainly caused by VT shifts under irradiation,and program and erase failures are mainly caused by increased Ioff,which overloads the charge pumping circuit.By varying the reference current,our 4 Mb NOR flash chip has the potential to survive a radiation dose of 1 Mrad(Si)in read mode.     

An improved OFDM chirp waveform used for MIMO SAR system

Special attention has been devoted to multi-input multi-output(MIMO)synthetic aperture radar(SAR)systems in recent years.The applications of MIMO SAR systems which involve 3D imaging,highresolution wide-swath remote sensing,and multi-baseline interferometry are seriously limited to the orthogonal waveforms.Although orthogonal frequency division multiplexing(OFDM)chirp waveforms can be used for MIMO SAR systems to avoid intra-pulse interferences,there is a small frequency shift between the transmitted OFDM pulses.This vulnerable shift,which can not only affect the waveform orthogonality,but also introduce residual phase error,renders the OFDM waveforms impractical.In this paper,an improved OFDM chirp waveform which works without the mentioned shift is presented,along with the novel modulation and efficient demodulation procedures.Comparison between the improved and the conventional OFDM chirp waveforms is detailed.The influence of random noise,quantization error,and Doppler shift on the orthogonality of OFDM waveform is also investigated in this paper.Theoretical analysis and simulation results illustrate the feasibility of this waveform scheme.     

OFDM wavefroms designed with piecewise nonlinear frequency modulation pulse for MIMO radar

ABSTRACT

Multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) waveform diversity design has drawn extensive attention since it has a great potential in remote sensing. The orthogonal frequency-division multiplexing (OFDM) waveform designing becomes one of the most significant tasks in MIMO SAR system. In this article, a novel piecewise nonlinear frequency modulation (NLFM) waveform is proposed. The OFDM waveform is composed of the piecewise NLFM waveforms as its subpulses, and each subpulse has a different subcarrier beginning frequency. The subpulse is centre symmetrical and can be divided into three segments. The first and third segments of the subpulse are linear frequency modulation waveforms, and the second segment of the subpulse is an NLFM waveform. A few parameters are used to control the duration and bandwidth of each segment in the subpulse. Genetic algorithm is used for the OFDM waveforms to optimize the sidelobes of autocorrelation and cross-correlation function. Compared with other OFDM waveform design methods, the proposed method is more flexible and has higher degrees of freedom and thus can yield waveforms with a better autocorrelation and cross-correlation properties. The performances of ambiguity function and cross ambiguity function are analysed to have low time delay and Doppler correlation peaks. Simulation results demonstrate the validity of the proposed method.     

Design and performance analysis of orthogonal coding signal in MIMO-SAR

Multi-input multi-output (MIMO) radar which has evident advantages in many applications is a new radar system.Applying the MIMO technique to the earth observing synthetic aperture radar (SAR) system offers effective ways for the improvement of high resolution and wide swath imaging and ground moving target indication (GMTI) systems.Designing the optimal orthogonal waveform is a crucial problem in the research on MIMO radar.First,the index definition of synthetic integrated side-lobe level ratio (ISLR) is pr...     

多发多收SAR编码正交信号设计及性能分析

多发多收(MIMO)雷达是一种新的雷达体制,具有许多突出的优点.将MIMO技术应用于对地观测的SAR系统,将为高性能地完成高分辨率、宽测绘带成像和GMTI等功能提供有效途径.正交波形优化设计是MIMO雷达研究中的基础性关键问题.首先针对SAR应用的特点,考虑同频编码正交信号之间互相关能量影响,提出了综合积分旁瓣比指标定义.然后通过理论分析和一维数值仿真论证了同频编码正交信号综合积分旁瓣比性能无法满足SAR成像的要求;再通过数值仿真验证了失配滤波处理仍然无法改善同频编码正交信号的综合积分旁瓣比性能.最后优化设计了一组相位编码正交信号作为MIMO-SAR发射信号,通过MIMO-SAR成像和InSAR仿真试验,进一步验证了分析结论的有效性.     

Clutter suppression and ground moving target imaging approach for hypersonic vehicle borne multichannel radar based on two-step focusing method

In this paper, a novel clutter suppression and ground moving target imaging approach is proposed for hypersonic vehicle (HSV) borne multichannel (MC) synthetic aperture radar (SAR) system. Compared with the traditional MC SAR ground moving target indication (GMTI) methods, the proposed algorithm can suppress clutter and decrease the moving target energy loss based on the improved MC clutter suppression method in the chirp Fourier transform (CFT) domain. Moreover, the moving target can be accurately focused by compensating the range curvature and the third order phase item. In addition, the motion parameters can be estimated precisely and the moving target can be focused accurately. Finally, the effectiveness of the proposed method is validated by the simulation examples.     

基于自聚焦的变门限SAR/GMTI动目标检测方法

高分辨率合成孔径雷达（Synthetic aperture radar,SAR）合成孔径时间长导致动目标散焦严重、信杂噪比（Signal clutter noise ratio,SCNR）降低,增加了对动目标的检测难度。针对这种情况,本文提出了一种基于自聚焦的变门限SAR/(Ground moving target indication,GMTI)动目标检测算法。该算法利用距离相位误差和方位相位误差之间存在的固定关系实现对动目标的两维相位误差的估计与补偿,达到提高SCNR的目的。通过两级不同门限的恒虚警率（Constant false alarm rate,CFAR）检测分别实现动目标检测和排除虚警。实测数据结果表明,本文算法能有效地检测动目标,降低虚警概率。     

基于背景图像集与稀疏分析的运动目标检测

组视频序列中得到系列背景图像,组合这些背景图像为背景集合。以图像块为基本单元,基于稀疏表示方法对图像块分析处理,提取运动目标。实验仿真表明该方法能够在环境光照突变时,有效消除噪声对目标检测的影响,降低目标检测的误检率,达到较为鲁棒的检测效果。     

一种鲁棒的三通道SAR慢动目标检测、定位算法研究

该文研究三通道合成孔径雷达(SAR)在通道不平衡条件下的慢动目标检测、定位问题。实际系统中,由于雷达系统存在通道幅相不一致等误差,干涉SAR/GMTI技术的杂波抑制性能急剧下降,无法检测慢动目标并进行定位。本文提出了一种分块SAR图像通道误差校正算法,进而采用空域自适应处理对慢动目标进行检测及定位。仿真实验表明该方案对系统误差的敏感度显著下降,具有很好的鲁棒性,非常适合实际工程实施。     

匀速运动目标的聚束SAR成像特征分析

运动目标的合成孔径雷达(SAR)成像特征是SAR/GMTI系统中进行运动目标检测和成像的基础.以往研究都是在两维可分离条带SAR成像算法条件下讨论目标运动对成像的影响,而很少考虑高分辨聚束SAR成像算法处理后运动目标的成像特征.本文推导了两种典型高分辨聚束SAR成像算法(RMA和PFA)处理后的动目标误差谱表达式,并在此基础上从目标几何定位误差、残留距离徙动和散焦等方面给出了完整的聚束SAR运动目标响应特征分析.最后通过仿真数据处理验证了分析结果.     

分布式星载SAR-GMTI系统仿真

仿真是进行分布式星载SAR地面动目标检测(GMTI)研究的重要方式。对分布式星载SAR-GMTI的系统仿真进行了全面讨论,内容包括地杂波建模\,动目标建模\,回波仿真方法、信号处理流程和方法,搭建了一个完整的仿真系统,用实验结果验证了该系统的可靠性。     

一种机载双通道SAR/GMTI自适应-通道均衡方法的研究

基于DPCA的机载SAR/GMTI系统中，通道幅相误差导致DPCA条件不满足，系统性能下降。在深入分析基于DPCA的双通道SAR/GMTI信号模型的基础上，给出了一种自适应通道均衡方法，给出了通道均衡的流程，分析了该均衡方法的性能。该方法使通道幅相特性在最小二乘意义下准确匹配，取消了系统对DPCA条件的严格要求。该均衡方法不需要天线参数平台运动参数等先验知识。     

炉膛声波飞行时间测量中声源信号的选取研究

炉膛内声波飞行时间的精确测量是实现声学法炉膛温度场分布测量技术的关键,而选取一种具有较强抗噪声干扰能力的声源信号是精确测量飞行时间的前提.针对适合于互相关函数法测量声波飞行时间的几种典型的声源信号,在不同信噪比下进行仿真实验比较,结果表明,线性扫频信号在相关法声波飞行时间测量中具有更强的抗噪声干扰能力;通过对不同声源信号进行功率谱分析得出,在采用互相关函数测量炉膛内声波飞行时间时,信号的抗噪声干扰能力不仅与信号的频率范围有关,而且还取决于其相对于噪声的有效频带.     

ISAR imaging via sparse frequency-stepped chirp signal

Frequency-stepped chirp signal can simplify the designation of radar system.However,it has a shortcoming of Doppler ambiguity for high-speed moving targets.Therefore,it is of great significance to study how to increase its equivalent pulse repeat frequency.The back scattering field of the ISAR target has strong sparsity;that is to say,most energy is contributed merely by a few scattering centers.Hence,based on the theory of the sparse signal representation,a novel method for ISAR imaging via sparse frequency-stepped chirp signals is proposed by analyzing the signal model of the target.In the proposed method,part of sub-pulses of the frequency-stepped chirp signal is randomly selected to transmit,and then the 2D high-resolution image of the target can be constructed by sparse signal decomposition.At the cost of computational resources,the method can effectively resolve the problem of Doppler ambiguity,decrease the sidelobes and obtain a super-resolution image.Furthermore,the validity of the proposed approach is confirmed by the results of numerical simulations and real data.     

MIMO雷达正交多相编码信号优化

为获得较好的波形分集增益与避免波形间串扰,MIMO（Multi-Input Multi-Output）雷达一般要求发射正交信号。已有的正交相位编码信号对多普勒偏移敏感,制约了其在MIMO雷达中的应用。提出一种具有较好多普勒容限的正交多相编码信号优化设计方法,联合考虑目标静止、匀速运动和匀加速运动场景下MIMO雷达脉压输出,并将其转化为一个多目标优化问题,基于自适应克隆选择算法进行求解。最后,进行仿真实验。结果表明,相比典型的Deng编码和Khan编码,设计的多相编码信号具有更好的正交性能、更大的速度、加速度容限,更适合MIMO雷达系统应用。     

An approach for refocusing of ground fast-moving target and high-order motion parameter estimation using Radon-high-order time-chirp rate transform

Long synthetic aperture time can improve the imaging quality of a ground moving target, whereas a moving target may be severely smeared in the cross-range image due to the range migration and the Doppler frequency migration. In this paper, the effects of the third-order Doppler broadening and Doppler ambiguity of a fast-moving target are considered. To address these issues, a novel motion parameter estimation method named high-order time-chirp rate transform (HTRT) is proposed, and then a new synthetic aperture radar (SAR) imaging method based on Radon-HTRT (RHTRT) for a ground moving target is developed. The major contributions are as follows: 1) The proposed SAR imaging method can eliminate the Doppler ambiguity effect. 2) The proposed method can realize longer time coherent integration than Radon–Fourier transform (RFT) and Radon–fractional Fourier transform (RFRFT) methods. 3) The proposed method is computationally efficient since HTRT can obtain the motion parameters of a moving target via performing the 2-dimensional (2-D) fast Fourier transform (FFT). Both the simulated and real data processing results show that the proposed method can finely image a ground moving target in a high signal-to-clutter and noise ratio (SCNR) environment.     

基于稀疏线性调频步进信号的ISAR成像

线性调频步进信号在简化雷达系统设计的同时,也存在对高速运动目标易出现Doppler模糊的问题,因此研究如何提高其等效的重复频率具有重要意义.由于ISAR目标的后向散射场具有较强的稀疏性,即大部分能量仅由少数散射中心贡献,所以本文基于稀疏信号表示理论,通过对目标回波模型的分析,提出了一种基于稀疏步进频率信号的逆合成孔径雷达成像方法.该方法通过随机地选择线性调频步进信号的部分子脉冲进行发射,然后使用稀疏信号分解的方法对目标图像进行重建以得到目标的二维高分辨图像.该方法以计算资源为代价,能够有效地去除方位Doppler模糊,同时还能够压低旁瓣并得到超分辨的图像.仿真和实测数据处理结果验证了本文方法的有效性.     

基于分数傅立叶变换的机载SAR多运动目标检测

机载合成孔径雷达（SAR）运动目标回波本质上为chirp信号,基于分数阶傅里叶变换（FRFT）的chirp基分解特性及分数阶傅立叶变换与时频分布的关系,给出了一种基于FRFT的针对强度相差较大的多运动目标检测方法。与传统的WVD方法相比,FRFT是一个线性变换,因此对于多个动目标就没有交叉项的干扰,简化了处理过程降低了处理复杂度。仿真结果验证了其有效性。     

Target models and waveform design for detection in MIMO radar

In this paper,we propose a general target model for multiple-input multiple-output(MIMO)radar.Two types of targets are presented.For each type of target,we develop a corresponding optimum waveform designing method to optimize detection performance.Based on Chernof-Stein lemma,we use relative entropy as the performance measure.We show that the optimum waveform designing method can obtain better detection performance than traditional orthogonal waveform designing method.     

Dual tree complex wavelet transform approach to copy-rotate-move forgery detection

As a common scheme of image tampering,copy-move forgery plays an important role in image forgery committee.Although several blind methods aimed at detecting replicated regions have been proposed,these methods cannot detect the rotation changes in the duplicated areas efciently.In this paper,a new forensic method is presented to detect the replicated areas rotated by arbitrary angles,even by JPEG compression.To achieve this,overlapping blocks of pixels are decomposed using dual tree complex wavelet transform(DTCWT),and then channel energies are extracted from each subband at each decomposition level using the L1norm.Finally,the anisotropic rotationally invariant features are extracted using magnitudes of discrete Fourier transform for these channel energies.The implementation procedure of the proposed method is described in detail.Extensive experimental results,including a comparative evaluation with existing methods and the special applications in practice,are also presented to demonstrate the robustness and efectiveness of the proposed method.