基于投影矩阵法的阵列天线波束形成方法

该文介绍一种阵列天线波束形成的新算法投影矩阵法,包括复系数、仅相位、仅幅度的波束形成技术,并推广应用到多目标波束综合设计中。文中首先给出采用投影矩阵法进行阵列天线复系数和仅相位波束形成的计算方法,然后提出仅幅度控制下的投影矩阵法,并进一步应用到多目标波束同时优化设计中。该文计算了多种工程应用例子,特别是满足全口径和多子孔径波束优化的仅幅度控制技术、满足多波束优化的仅相位控制及共用幅度优化技术,对算例的设计达到了采用优化激励系数控制波束指向、波束赋形、旁瓣电平等性能要求,实现了阵列天线的波束形成。仿真结果说明了投影矩阵法的有效性,适用范围广泛。      

基于波束优化赋形方法的斜视星载SAR模糊抑制研究

距离模糊和方位模糊会严重影响星载合成孔径雷达（Synthetic Aperture Radar,SAR）的成像质量。现有的利用天线波束赋形来抑制模糊的方法在雷达正侧视成像时取得了优异的效果,但并不适用于雷达斜视的情况。针对这一问题,提出了一种基于平面阵列天线波束赋形的星载SAR二维模糊（距离和方位模糊）抑制方法。使用距离-方位模糊综合的模糊比（Ambiguity to Signal Ratio,ASR）指标来替代距离模糊比及方位模糊比,结合对不同斜视情形下天线波束变化的分析,充分考虑包含镜像模糊区在内的所有模糊区,建立了模糊比-天线权重优化模型。以模糊能量为目标函数、天线方向图掩模作为约束确立二次锥（Quadratic Cone Programming,QCP）优化问题,求解得到阵元幅度相位分布。仿真结果表明,所提方法可以通过调节模糊区对应的旁瓣幅值,灵活地抑制SAR斜视成像的距离和方位模糊,进而提高星载SAR的成像质量。     

Optimization of SAR distributions in liver and lung regionsirradiated by the H-horn annular phased array hyperthermiasystem

The author discusses a type of annular phased array (APA) system-the H-horn APA. The phase and amplitude control of power deposition patterns for this system have been theoretically analyzed at a frequency of 200 MHz. The formulas for calculating the electric field (E-field) and specific absorption rate (SAR) for this APA system have been derived and can be applied to other types of APA systems. Models on computerized tomography (CT) scans from liver and lung regions have been used for predicting optimization of the E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the phase and amplitude control of SAR patterns results in a more selective and effective heating of tumors situated eccentrically and deeply within the body. The numerical results indicate that it is possible to shift the absorbed power patterns by electrically varying the phase and/or the amplitude of the sources and manually moving the positions of the horns     

Synthetic bandwidth method and experimental research based on a wideband multi-channel SAR

Synthetic bandwidth technique is used to increase frequency bandwidth of the system and provides an effective way to achieve the ultra high resolution in the field of Synthetic Aperture Radar (SAR). But in the actual SAR system, the synthesis result will be seriously deteriorated by the inner-channel and inter-channel phase error. A frequency domain synthetic bandwidth method based on transfer function extracting technique is proposed in an actual SAR system which consists of single wideband transmit channel and 8-way down-conversion receive sub-channels. The method can accurately get the amplitude and phase characteristics of the sub-channel and compensate the amplitude-phase errors. The final experimental results demonstrate the validity and feasibility of the method and the range resolution down to 0.1 m is obtained.     

Ka波段高精度模拟预失真线性化器

模拟预失真技术是改善行波管放大器非线性失真的一种有效方法,但补偿精度较低的缺点是制约其进一步发展的关键因素。增益相位独立调节技术和补偿曲线形状调节技术是提升模拟预失真补偿精度的重要技术。提出了一种适用于Ka波段行波管放大器的高精度模拟预失真器,该预失真器采用双路矢量合成式结构,在29~31 GHz 范围内,通过调节二极管偏置电压可以同时实现补偿曲线形状调节和增益相位扩张量独立调节,有效提升了补偿精度。与行波管放大器的联合测试结果表明,在30 GHz 时,该预失真器可以将行波管放大器的增益压缩从5.3 dB 减小到1.2 dB,相位偏移从62°减小到6.5°。线性化后的行波管放大器的非线性失真明显降低,在输出功率回退5 dB 时,三阶互调系数提高了9.3 dB。     

一种改进的机载前斜视SAR二次距离压缩成像算法

该文基于斜视距离模型,直接推导了适用于大斜视合成孔径雷达(SAR)成像的二次距离压缩(SRC)算法,在此基础上提出了一种改进的机载前斜视SAR的SRC成像算法。通过补偿距离频率的三次相位项,有效改善了大斜视SAR成像距离压缩旁瓣非对称畸变的问题,通过补偿波束前视引入的平动相位项,解决了图像位置在方位向发生偏移的问题。给出了实现步骤和算法流程,对比了不同斜视角情况下算法改进前后的成像效果。仿真表明,该算法能有效改善大斜视SAR的成像质量,适合于大斜视机载SAR成像。     

Theoretical Analysis and Clinical Demonstration of the Effect of Power Pattern Control Using the Annular Phased-Array Hyperthermia System

The phase and amplitude control of power deposition patterns for the BSD Annnlar Phased Array (APA) has been theoretically analyzed at a frequency of 60 MHz. Absorbed power patterns in simple circular cross-sectional cylindrical dielectric structures were studied first to compare with published experimental results. Models based on computerized tomography (CT) scans from the pelvic region have been used for predicting the specific absorption rate (SAR) patterns in patients. Significant changes were observed with phase changes of 30° and relative amplitude changes of 20 percent. The theoretical predictions qualitatively agree with the experimental results reported for simple phantoms. It is also shown that these techniques result in a better control of the SAR patterns and thus more effective heating of tumors situated eccentrically within the pelvis, which we have confirmed in clinical treatments.     

Key technology of D-InSAR at X-band for monitoring land subsidence in mining area and its application

In theory, land subsidence measurement results with high accuracy can be obtained by using the Differential Interferometry Synthetic Aperture Radar （D-InSAR） at X-band. In practice, however, the measuring accuracy of D-InSAR at X-band has been seriously affected by some factors, e.g., decorrelation and high deformation gradient. In this work, the monitoring capability of D-InSAR for coal-mining subsidence is evaluated by using SAR data acquired by TerrraSAR-X system. The SAR image registration method for low coherence image pairs, the denoising phase filter for high noise level interferogram and atmospheric effects mitigation method are the key technical aspects which directly influence the measurement results of D-InSAR at X-band. Thus, a robust image registration method, an improved phase filter method and an atmospheric effects mitigation method are proposed in this paper. The proposed image registration method successfully achieves InSAR coregistration, while the amplitude cross-correlation cannot properly coregister low coherence SAR image pairs. Moreover, the time complexity of the proposed image registration method is obviously slighter than that of the Singular Value Decomposition （SVD） method. The comparing experiment results and the unwrapping phase results show that the improved Goldstein filter is more effective than the original Goldstein filter in noise elimination. The atmospheric influence correction experiment results show that the land subsidence areas with atmospheric influence correction are more clarified than that of without at- mospheric influence correction. In summary, the presented methods directly improved the measurement results of D-InSAR at X-band.     

SAR图像幅度域增强的正则化方法

正则化方法通过增加先验信息约束,达到增强SAR图像特征的目的。在分析现有先验信息约束条件的基础上,提出SAR图像幅度域上的正则化增强方法,从理论上证明了SAR图像复数域上正则化方法和幅度域上正则化方法的等价性,进一步解释了正则化方法的相位保持特性,提高了计算效率。通过参数变换,结合先验信息,给出正则化参数的选取方法,该方法操作简单,能有效地抑制噪声,保护目标。最后利用仿真图像和MSTAR图像验证了该方法的有效性。     

CS算法结合COAA算法提高机载合成孔径雷达成像质量

该文将对比度最优自聚焦算法(COAA)与基本Chirp Scaling算法(CSA)相结合,对CS算法方位处理过程做适当变化,把COAA算法融入其中,一方面进行精确的无插值距离徙动校正,一方面进行准确的二次相位误差估计和校正,从而提高机载合成孔径雷达的成像质量。通过对COAA算法采用变步长迭代提高二次相位误差估计的精度和速度,增强算法的实用性。文中给出两种算法相结合进行雷达数据成像处理的流程图,并用条带正侧视SAR模式实际雷达数据验证研究结果的有效性。     

数字波束形成在雷达中的应用与分析

本文对数字波束形成技术在雷达系统中的应用进行深入讨论,介绍了数字波束形成的电路设计和波束设计。对于多通道幅相差异的检测和校正,即接收校正和发射校正,给出了详细的工程设计方法和推导公式。试验表明,数字波束形成技术的应用,提高了三坐标雷达的测高精度和系统可靠性。文中的内容在某三坐标雷达产品中已获得成功应用,技术可靠有效。     

几种数字波束零点形成方法的比较

在概述数字波束零点形成加权结构的基础上,给出了幅度相位加权、仅相位加权和混合控制加权三种算法,并进行了比较：幅度相位加权方法形成零点的效果最好,但算法比较复杂;仅相位加权算法运算简单、有利于硬件实现,但只在零点处于特定位置时效果较好;混合控制加权算法实现灵活,但对受控阵元位置要求较高,具有较强的发展潜力。文中最后采用计算机仿真验证了理论分析结果。     

用于机载SAR的距离向波束赋形微带天线阵的研究

通过对宽测绘带的机载合成孔径雷达距离向回波特性的分析,推导出了天线距离向辐射赋形方向图表达式。利用Schelkunoff单位圆结合零限填充对天线阵进行综合,得到了天线各单元激励幅度和相位,并利用微带贴片天线阵列实现赋形波束方向图。该文用两种介质配置分别加工了实验样阵列,实验结果、仿真结果与理论综合结果三者吻合较好,从而证明了赋形方法正确,技术路线可行。     

基于随机并行梯度下降算法光纤放大器相干合成的动态模拟与控制带宽分析

对随机并行梯度下降(SPGD)算法校正时变相位噪声的动态过程进行数值模拟,计算不同强度和频率的相位噪声对控制带宽的影响程度,分析控制带宽与光束数目以及算法执行速度之间的关系.计算结果表明,随着相位噪声强度和频率的增加,算法的控制带宽随之减小,带宽大小与参与合成的光束数目N的-4/3次方成正比,与算法执行速度成线性关系.计算结果可为SPGD算法应用至多路高功率光纤放大器相干合成提供参考.     

基于内定标信号的合成孔径雷达系统幅相误差的提取和校正

该文根据合成孔径雷达的三路定标设计,提出了基于内定标信号的收发系统幅相误差的提取和校正方案。与从雷达回波数据中提取系统相位误差的方法相比,该方案具有两方面的优越性:提取误差不受地物特性的限制,使用方便;不但可以提取相位误差,还可以提取系统幅度误差。经验证该方案能大大改善图像质量。     

超宽带SAR虚假图像干扰技术

为了对低频超宽带合成孔径雷达(SAR)实施有效的图像欺骗干扰,提出基于卷积技术的欺骗干扰方法。基于SAR目标回波特性,推导了干扰调制函数解析式。在产生干扰信号时,需要对解析式进行近似处理,针对低频超宽带SAR二维强耦合特性以及超宽带SAR成像处理算法,将干扰调制函数精确到三次相位项,并对各级系数进行分析和简化处理。最后通过仿真实例验证了对干扰产生函数改进的必要性及干扰的有效性。理论分析和仿真结果均表明,改进后的干扰方法可以对超宽带SAR实施有效的图像欺骗干扰。     

Phase and amplitude phase restoration in synthetic aperture radarimaging

Methods for addressing two types of multiplicative noise in synthetic aperture radar (SAR) imaging are presented. The authors consider a multiplicative noise with a real phase (i.e. the SAR signal's phase is contaminated but its amplitude is uncorrupted) that possesses unknown functional characteristics with respect to the radar signal's temporal frequencies. A perturbation solution for phase reconstruction from amplitude is developed from a wave equation governing the SAR signal and a Riccati equation that relates the amplitude and phase functions of the SAR signal. This solution is converted into a noniterative analytical solution in terms of the moments and powers of the log amplitude function. Next, the authors consider a multiplicative noise with a complex phase (i.e. both the amplitude and phase of the SAR signal are contaminated) that varies linearly with respect to the radar signal's temporal frequencies. The two wave equations governing the SAR signal at two temporal frequencies of the radar signal are combined to derive a method to reconstruct the complex phase error function.     

一种归一化QPLL的未知时变谐波噪声主动控制算法

针对船舶机械未知时变谐波噪声的主动控制问题,基于正交锁相环原理,提出了一种归一化QPLL（Quadrature Phase Locked Loop）的未知时变谐波噪声主动控制方法.通过在相位/频率更新结构中引入参数调整因子,形成一种改进的QPLL结构;引入次级通道,设计并提出了基于QPLL的未知时变谐波噪声控制算法.首先,通过平均化理论和线性化方法,分析该算法的稳定性,指出了次级通道特性和谐波信号幅值对该算法收敛性能的影响;其次,基于分析结果,引入次级通道、幅值归一化措施,形成一种归一化的未知时变谐波噪声主动控制算法,提升稳定性能和收敛速度;最后,通过仿真验证了归一化改进措施对未知时变谐波噪声主动控制算法综合性能的改善效果.     

光寻址液晶空间光调制器用于激光光束整形的可控系统和设计算法

提出了一种利用光寻址液晶空间光调制器(LC-SLM)来实现实时可控的激光光束整形的系统和算法.用几何变换法和盖师贝格-撒克斯通(G-S)算法对有振幅调制和位相畸变光束进行均匀分布的平顶光束整形及数值模拟,用几何变换法可以得到非常好的小尺度的均匀性输出光束,而G-S算法能够有效地改善入射光束的大尺度不均匀性.为了减少输出光束的均方根误差和顶部不均匀度,提出结合几何变换方法和G-S算法,由几何变换方法得到的相位分布为G-S算法的初始相位分布.计算机设计的仿真结果表明:利用这种算法可以有效减少大尺度的不均匀度值,并得到合适的输出光束.     

Theoretical analysis of H-Horn annular phased array system for heating deep-seated tumors

This paper discusses a type of annular phased array system--H-Horn APA. The phase and amplitude control of power deposition patterns for this system are theoretically analyzed at a frequency of 200 MHz. The formulas for calculating E-field and SAR for this APA system are derived, and can be applied to other type APA systems. Models of computerized tomography (CT) scans from liver and lung regions have been used, respectively, for predicting optimization of E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the techniques of the phase and amplitude control of SAR patterns result in more selectively and effectively heating of tumors situated eccentrically and deeply within bodies of patients. The APA hyperthermia described in this paper shows great promise, and it looks very useful for developing clinical applications.