STUDY ON THE SIGNATURE OF GROUND MOVING TARGET FOR AIRBORNE SQUINT SAR IMAGING

Compared with the side-looking Synthetic Aperture Radar (SAR), the flexible beampointing of squint SAR makes great application value. This paper derives the image signature of the ground moving target after the processing of Range-Doppler (RD) algorithm, the SAR signatures of ground moving targets are analyzed, including the geometry correction, the offsets and defocusing in both range and azimuth direction. Finally, computer simulation results validate its effectiveness. The research results are especially significant for moving targets detection and parameters estimation in squint mode SAR.

An approach to wide-field imaging of linear rail ground-based SAR in high squint multi-angle mode

Ground-based synthetic aperture radar(GB-SAR) has been successfully applied to the ground deformation monitoring.However, due to the short length of the GB-SAR platform, the scope of observation is largely limited. The practical applications drive us to make improvements on the conventional linear rail GB-SAR system in order to achieve larger field imaging. First, a turntable is utilized to support the rotational movement of the radar.Next, a series of high-squint scanning is performed with multiple squint angles. Further, the high squint modulation phase of the echo data is eliminated. Then, a new multi-angle imaging method is performed in the wave number domain to expand the field of view. Simulation and real experiments verify the effectiveness of this method.

Compact wideband microstrip array antenna with beam squint

A compact wideband microstrip array antenna with a squint beam is introduced without the matched load. Its measured beam is at 10° offset to the broadside with a measured gain of 12 dB at 10 GHz. The measured impedance bandwidth （voltage standing wave ratio （VSWR）≤2） is over 16%, which agrees well with the simulated one. It is a low-cost wideband design with compact simple structure, suited for military and commercial application.

NOVEL APPROACH BASED ON DERAMPING TECHNIQUE FOR SQUINTED SLIDING SPOTLIGHT SAR IMAGING

This paper investigates a novel approach based on the deramping technique for squinted sliding spotlight Synthetic Aperture Radar (SAR) imaging to resolve the azimuth spectrum aliasing problem. First of all, the properties of the azimuth spectrum and the squint angle impacts on the azimuth spectrum aliasing problem are analyzed. Based on the analysis result, an operation of filtering is added to the azimuth preprocessing step of traditional Two-Step Focusing Approach (TSPA) to resolve the azimuth folding problem and remove the influence of the squint angle on the azimuth spectrum aliasing problem. Then, a modified Range Migration Algorithm (RMA) is performed to obtain the precise focused image. Furthermore, the focused SAR image folding problem of traditional TSPA is illuminated in this paper. An azimuth post-processing step is proposed to unfold the aliased SAR image. Simulation experiment results prove that the proposed approach can solve the spectrum aliasing problem and process squinted sliding spotlight data efficiently.

Study of a millimeter-wave squint indirect holographic algorithm suitable for imaging with large field-of-view

In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the background and twin- image interferences, which achieves a similar effect to off-axis holography but leaves out the large-aperture quasi-optical component. The translational scanning manner enables a large field of view and ensures the image uniformity, which is difficult to realize in off-axis holography. In addition, a corresponding imaging algorithm for the presented scheme is developed to reconstruct the image from the recorded hologram. Some imaging results on typical objects, obtained with electromagnetic simulation, demonstrate good performance of the imaging scheme and validate the effectiveness of the image reconstruction algorithm.

THE STRIP IMAGING OF AIRBORNE SQUINT SIDELOOKING MODE SAR

Airborne squint side-looking strip imaging mode SAR has the advantages of better flexibility and larger field in applications than the classic side-looking mode SAR. Because of the large range migration and serious range-azimuth coupling terms, the imaging processing of squint mode SAR is a full two-dimensional (2-D) phenomenon. In this paper, different algorithms, which can be used for the imaging processing of squint mode SAR, are compared with each other in terms of their focusing quality and their ability to handle the large range migration of the squint side-looking mode SAR. And their abilities of real-time imaging are also discussed. The algorithms contained here are 2-D FFT method, fast polynomial transform(FPT) method, and the direct correcting method based on range-Doppler focusing algorithms. Other new methods are also discussed here briefly.

SIDE-LOOKING ECHO DATA TRANSFORM TO SQUINT MODE SAR IMAGING

Nowadays the side-looking SAR echo data can be obtained easily from the commercial channel, while that of other SAR imaging modes such as squint, spotlight are difficult to be acquired. This paper presents a new scheme to transform the side-looking returns to squint ones, in a direct and an indirect approach respectively. Direct transformation uses the data with a wide azimuth beam angle. The maximum of the required squint angle is limited under several degrees. Squint data under indirect transformation can be obtained by adding a platform velocity along slant range according to the required squint angles. Then the squint data is determined by the angle between the new forward velocity and line-of-sight direction. This method results in higher squint angle compared with the first one. Verification shows the feasibility of these approaches with illustration of side-looking E-SAR raw data processing. The future work will be on the precise Doppler centroid estimation and effective imaging algorithm development.

栅格空间Squint/Opera墨尔本办公室

动画与视觉艺术工作室Squint/Opera是墨尔本具有领先水平的动漫创作机构之一。它的新办公总部位于一个商业中心的地下一层。尽管这家公司的动画师们每天都要创造大量的虚拟场景,却仍然脱离不了物质世界带来的桎梏。今年年初,Squint/Opera找到SIBLING建筑事务所,希望设计师为他们打造一个全新的工作场所,使公司性质与空间特征能够融合在一起,让办公室成为虚拟与现实的交汇之地。

改良耳穴压豆联合局部按摩治疗儿童特发性异常瞬目症的临床研究

目的 观察改良耳穴压豆联合局部按摩治疗儿童特发性异常瞬目症的临床疗效。方法 纳入2019年10月—2022年4月在上海市松江区中心医院眼科门诊确诊的4~12岁特发性异常瞬目症患儿90例,随机分成观察组(A组)、中医组(B组)和对照组(C组)各30例(60只眼)。分别予改良耳穴压豆、经典耳穴压豆和常规心理—行为疗法配合滴眼液治疗。3组均观察21 d。分别于治疗前、治疗后测量患儿瞬目频率、学习能力的数据。结果(1)瞬目频率评分:3组治疗前瞬目频率评分比较,差异无统计学意义(P>0.05)。治疗后A组与B组瞬目频率评分均较治疗前降低,差异均有统计学意义(t_(A组)=19.313、t_(B组)=15.000,均P=0.000),C组较治疗前,差异无统计学意义(P>0.05)。治疗后3组间比较,差异有统计学意义(F=1093.886,P=0.000)。与C组比较,A组和B组瞬目频率评分均较低,差异均有统计学意义(t_(A组)=-11.655,t_(B组)=-11.171,均P=0.000);A组和B组比较,差异无统计学意义(P>0.05)。(2)阅读速度比较:治疗后A组与B组阅读速度均较治疗前增加,差异均有统计学意义(t_(A组)=-60.647,t_(B组)=-61.465,均P=0.000),C组较治疗前,差异无统计学意义(P>0.05)。治疗后3组间阅读速度比较,差异有统计学意义(F=19.150,P=0.000)。与C组比较,A组与B组阅读速度均较快,差异均有统计学意义(t_(A组)=4.744、t_(B组)=4.033,均P=0.000);A组与B组比较,差异无统计学意义(P>0.05)。(3)听写速度比较:治疗后A组与B组听写速度均较治疗前增加,差异均有统计学意义(t_(A组)=-115.348、t_(B组)=-109.133,均P=0.000),C组较治疗前,差异无统计学意义(P>0.05)。治疗后3组间比较,差异有统计学意义(F=91.933,P=0.000)。与C组比较,A组与B组听写速度均较快,差异均有统计学意义(t_(A组)=9.751、t_(B组)=8.203,均P=0.000);A组与B组听写速度比较,差异无统计学意义(P>0.05)。(4)中医症候积分:3组治疗前中医症候积分比较,差异无统计学意义(P>0.05)。治疗后A组与B组中医症候积分均较治疗前降低,差异均有统计学意义(t_(A组)=-4.365、t_(B组)=-4.062,均P=0.000),C组较治疗前,差异无统计学意义(P>0.05)。治疗后3组间比较,差异有统计学意义(F=17.259,P=0.000)。与C组比较,A组和B组中医症候积分均较低,差异均有统计学意义(t_(A组)=-4.979、t_(B组)=-4.625,均P=0.000);A组和B组比较,差异无统计学意义(P>0.05)。(5)临床疗效:A组(96.67%)与B组(93.33%)总有效率均优于C组(66.67%),差异均有统计学意义(χ^(2) A组=9.017,P=0.003;χ^(2) B组=6.667,P=0.010),而A组与B组比较,差异无统计学意义(P>0.05)。(6)复发率:A组(10.34%)与B组(14.29%)复发率均低于C组(80.00%),差异均有统计学意义(χ^(2) A组=24.191、χ^(2) B组=20.728,均P=0.000);而A组与B组比较,差异无统计学意义(P>0.05)。结论 改良耳穴压豆联合局部按摩治疗儿童特发性异常瞬目症临床疗效较好,具有操作简单、疗效可靠、复发率低等优势,值得临床推广。

Squint-mode InISAR imaging based on nonlinear least square and coordinates transform

Aiming at the interferometric inverse synthetic aperture radar （InlSAR） imaging in the presence of squint, we investigate the influence of squint on the InlSAR imaging. First, coupling of the squint additive phase and the target azimuth/altitude coordinates to be solved may make the solution more difficult. Second, the squint angle may lead to estimation error of the vertical coordinates and distortion of the ultimate image. Traditional InlSAR imaging algorithms can not solve the above two problems effectively, so we propose a new method which combines the nonlinear least square （NLS） and coordinates transform （CT） to estimate the target coordinates, and a three-dimensional （3-D） image consistent with the real target is obtained accordingly. Simulations show that the proposed method is effective for the squint-mode InlSAR imaging.

一种适用于星载大斜视聚束SAR的改进距离徙动算法

星载大斜视聚束合成孔径雷达(Synthetic Aperture Radar,SAR)探测范围大、目标驻留时间长,有广泛的应用前景,但会带来较大的距离徙动,使得回波信号耦合严重。传统算法使用固定窗接收数据,为了采集完整,则需要较大的采样窗,但采得数据中存在大量的无效数据,采样效率很低。为解决时域采样效率低等问题,可使用滑窗接收模式,但该模式一般结合时域算法或极坐标格式算法使用,而在星载SAR大场景成像的情况下,时域算法计算效率低下,极坐标格式算法的聚焦半径较小,因此本文提出了一种改进的距离徙动算法来解决大斜视滑窗接收模式下的高效精确成像问题。本文建立了滑窗接收模式下的时域回波模型,利用傅里叶变换的性质推导出精确两维解析频谱,并基于上述两维解析频谱,提出雷达视线坐标系下的两维空间域解耦方法并给出对应的完整成像处理流程,最后通过仿真实验验证算法的有效性。本文提出的新方法既能解决大斜视两维频谱扭曲带来的频域采样效率低下问题,又可避免传统方法在大斜视模式下的残留距离徙动放大问题,为后续的自聚焦处理提供便利。

基于分数阶傅里叶变换和图像加权熵的chirp scaling算法

针对传统的基于傅里叶变换和匹配滤波实现的chirp scaling(CS)成像算法中多普勒参数随斜距变化以及成像分辨率低的问题,提出利用分数阶傅里叶变换(FRFT)对CS成像算法进行优化。首先建立斜视合成孔径雷达(SAR)回波信号模型,理论推导利用FRFT代替匹配滤波进行信号压缩。针对方位向最优旋转角的搜索问题,对得到的图像基于加权最小熵建立代价函数,利用动量法的梯度下降优化算法进行迭代计算,最终得到分辨率更高的SAR图像。为验证算法的有效性,分别在点目标仿真数据和实测SAR数据集上进行实验。结果表明,与传统CS成像算法相比,该算法的成像结果成像主瓣宽度更窄、旁瓣更低、成像更加清晰。

基于椭球模型的斜视星载SAR距离模糊仿真

距离模糊比是星载SAR图像的一项重要指标,与正侧视成像相比,大斜视成像星地几何关系更为复杂,传统距离模糊计算与仿真中将地球视为球体的假设会对计算结果造成较大偏差,不能准确评估SAR图像质量。本文采用更为准确的地球椭球模型代替球体模型,并提出了一种基于斜视天线坐标系的模糊区计算方法,利用此方法对距离模糊比沿距离向测绘带的变化进行仿真,同时对距离模糊比沿方位向的空变性也进行研究。本文研究成果对星载SAR系统设计具有重要参考价值。

Beam squint effect on high-throughput millimeter-wave communication with an ultra-massive phased array

An ultra-massive phased array can be deployed in high-throughput millimeter-wave(mmWave)communication systems to increase the transmission distance.However,when the signal bandwidth is large,the antenna array response changes with the frequency,causing beam squint.In this paper,we investigate the beam squint effect on a high-throughput mmWave communication system with the single-carrier frequency-domain equalization transmission scheme.Specifically,we first view analog beamforming and the physical channel as a spatial equivalent channel.The characteristics of the spatial equivalent channel are analyzed which behaves like frequency-selective fading.To eliminate the deep fading points in the spatial equivalent channel,an advanced analog beamforming method is proposed based on the Zadoff-Chu(ZC)sequence.Then,the low-complexity linear zero-forcing and minimum mean squared error equalizers are considered at the receiver.Simulation results indicate that the proposed ZC-based analog beamforming method can effectively mitigate the performance loss by the beam squint.

可重构智能表面辅助的多用户通信宽带信道估计

针对太赫兹(THz)链路的严重传输衰减和宽带系统中波束斜视导致传统信道估计方案性能下降的问题,该文构建了可重构智能表面(RIS)辅助多用户THz通信模型,并提出一种低复杂度的两阶段级联信道估计方案。在第1阶段,利用THz的稀疏性和对数和函数,将信道估计问题转化为目标优化问题,通过梯度下降法优化目标函数,使待估信道参数迭代逼近最优解,从而估计出典型用户级联信道;在第2阶段,利用其他用户的级联信道与典型用户信道的强相关性,以较低的导频开销来估计其他用户的级联信道。仿真结果表明,所提方案相较于其他方案具有更好的性能。

新斜视钩下穹窿结膜小切口斜视手术对水平斜视患者的疗效

目的探究新斜视钩下穹窿结膜小切口斜视手术对水平斜视患者眼球运动、视力的影响。方法选取本院于2019年10月~2021年10月收治的行新斜视钩下穹窿结膜小切口斜视手术的患者49例(98眼)。术后随访6月,观察患者疗效、眼球运动及视力情况、结膜切口、并发症发生情况。结果术后治疗有效率为93.88%(46/49);术后眼球运动自由48例(69眼)占97.96%,术前术后视力无变化;行结膜切口19例(38.78%);并发症:术后出现3例(6眼),发生率6.12%,包括结膜息肉2例(4眼)、结膜囊肿1例(2眼)。结论采用新斜视钩下穹窿结膜小切口斜视手术治疗水平斜视患者可显著提升疗效,降低并发症发生率,保证患者预后,可应用于临床。

糖尿病性眼肌麻痹临床报道1例及文献回顾

糖尿病引起神经系统并发症,其中累及周围神经最常见,颅神经较少受累,糖尿病性眼肌麻痹是颅神经受累表现,其约占糖尿病并发症的0.4%~5%。作者在临床上运用中西医结合方法治疗糖尿病性眼肌麻痹1例,同时查阅相关文献对糖尿病性眼肌麻痹的发病机制、临床表现、诊断依据、中西医治疗等方面进行全面的文献回顾。

直角三棱镜和等腰三棱镜测量斜视角的比较

目的:探讨直角三棱镜和等腰三棱镜测量斜视角的差异。方法:病例对照研究,选取2021-06/2022-04我院住院共同性斜视患者176例,其中共同性内斜视患者79例,共同性外斜视患者97例。所有患者分别运用交替遮盖直角三棱镜和等腰三棱镜中和法进行斜视角测量。结果:共同性内斜视患者直角三棱镜测量结果为49.167△±13.573△,等腰三棱镜测定结果为38.250△±10.756△(P<0.01),两者差值为10.917△±3.752△;直角三棱镜测量值转换为圆周度为19.096°±2.456°,等腰三棱镜为20.847°±5.364°(P<0.05),两者差值为2.443°±2.702°;共同性外斜视患者直角三棱镜测量结果为51.875△±13.567△,等腰三棱镜测量结果为40.492△±11.753△(P<0.01),两者差值为11.383△±4.783△;直角三棱镜测量值转换为圆周度为19.589°±2.521°,等腰三棱镜为21.947°±5.864°(P<0.01),两者差值为3.200°±3.077°。两种类型斜视患者使用不同三棱镜检测结果差值及转化为圆周度比较均无差异(P>0.05)。结论:直角三棱镜和等腰三棱镜查斜视角存在差别,直角三棱镜测定的斜视度大于等腰三棱镜。

星载方位多通道斜视SAR对运动目标成像方法

由于受到斜视角和运动速度的影响,方位多通道合成孔径雷达(SAR)的方位模糊和速度模糊问题更加严重,从而影响斜视模式下运动目标的多通道重建与成像。为了解决该问题,文章提出了一种星载方位多通道斜视SAR运动目标成像方法。首先,分析并建立斜视模式下运动目标精确回波模型,然后,基于谱估计及改进Radon变换实现运动目标无模糊径向速度估计,对目标二维频谱进行匹配滤波实现运动目标成像。最后,点目标仿真实验验证了该方法的有效性。

基于改进PFA的车载大斜视SAR成像算法

为了应对车载毫米波雷达大斜视成像困难的问题,本文提出一种改进的极坐标格式算法(Polar Format Algorithm,PFA)对条带车载毫米波雷达斜视回波进行基于子孔径拼接的成像。该算法从条带数据与聚束数据的特点出发,将全孔径回波划分为子孔径,利用PFA处理子孔径数据。由于PFA存在波前弯曲误差,子图像不能直接拼接,因此对每一幅子图像进行几何失真校正。同时,以重叠子孔径的划分方式保证成像结果的高分辨率。最后截取子图像进行拼接得到条带SAR成像结果。所提方法解决了车载毫米波雷达大斜视情况下两维耦合严重的问题。通过对点目标和实测数据的仿真与分析验证了所提方法的有效性。