Complex SAR Image Compression Using Entropy-Constrained Dictionary Learning and Universal Trellis Co ded Quantization

In this paper, an Entropy-constrained dic-tionary learning algorithm (ECDLA) is introduced for e?-cient compression of Synthetic aperture radar (SAR) com-plex images. ECDLA RI encodes the Real and imaginary parts of the images using ECDLA and sparse representa-tion, and ECDLA AP encodes the Amplitude and phase parts respectively. When compared with the compression method based on the traditional Dictionary learning al-gorithm (DLA), ECDLA RI improves the Signal-to-noise ratio (SNR) up to 0.66dB and reduces the Mean phase error (MPE) up to 0.0735 than DLA RI. With the same MPE, ECDLA AP outperforms DLA AP by up to 0.87dB in SNR. Furthermore, the proposed method is also suitable for real-time applications.     

Combination of sorption properties of polydimethylsiloxane and solid‐phase extraction sorbents in a single composite material for the passive sampling of polar and apolar pesticides in water

Passive sampling techniques have been developed as an alternative method for in situ integrative monitoring of trace levels of neutral pesticides in environmental waters. The objective of this work was to develop a new receiving phase for pesticides with a wide range of polarities in a single step. We describe the development of three new composite silicone rubbers, combining polydimethylsiloxane mechanical and sorption properties with solid‐phase extraction sorbents, prepared as a receiving phase for passive sampling. A composite silicone rubber composed of polydimethylsiloxane/poly(divinylbenzene‐co‐N‐vinylpyrrolidone) was selected by batch experiments for its high sorption properties for pesticides with octanol‐water partition coefficients ranging from 2.3 to 5.5. We named this composite material “Polar/Apolar Composite Silicone Rubber”. A structural study by scanning electron microscopy confirmed the homogeneous dispersion of the sorbent particles and the encapsulation of particles within the polydimethylsiloxane matrix. We also demonstrate that this composite material is resistant to common solvents used for the back‐extraction of analytes and has a maximal resistance temperature of 350°C. Therefore, the characteristics of the “Polar/Apolar Composite Silicone Rubber” meet most of the criteria for use as a receiving phase for the passive sampling of pesticides.     

天线-罩系统的散射计算

应用物理光学法(PO)对天线-罩系统的散射特性进行分析。通过对罩壁的局部平板等效,导出了天线表面的感应电流和罩表面的等效电、磁流分布的计算公式。以口径天线-多层介质结构雷达罩为例,计算了天线、雷达罩及天线-罩系统的单、双站雷达散射截面(RCS),并研究了当照射波频率和天线扫描角变化时RCS的变化规律。     

机载雷达罩曲面FSS阵图形制作研究

采用电镀铜箔蚀永不地和图形电镀反贴法,研究了雷达工面ＦＳＳ阵图形制作工艺,解决了液态光抗蚀油墨的立体涂布、底片分割贴装、旋转狭缝曝光及蚀刻问题;另外还解决了图形电镀、压模反贴问题。图形精度分别达到±０．０８ｍｍ和±０．０６ｍｍ,满足≤±０．１０ｍｍ的图形公差要求。     

基于分形压缩特征的雷达目标识别研究

利用分形构形的基本理论,对雷达目标散射回波信号进行分形压缩逼近,通过分析压缩,对原始散射信号波形数据进行压缩,从而有利于目标识别．有此基础上,利用散射回波信号的分形压缩特征进行了目标识别研究．实验仿真结果证实本文方法行之有效     

美军炮位侦校雷达新进展

详细介绍美军炮位侦察雷达的改进情况以及新型炮位侦察雷达的研制情况。     

天气雷达频率源设计

介绍天气雷达频率源的要求及重要性,给出不同频段的几种设计方案及工程设计的几个重要问题,分析实现低相噪频率源设计的电磁兼容问题。     

Geometrical Form Factor Improvement for Receiving System of Infrared Lidar

Improvement of an infrared light detection and ranging (IR-lidar) system for a short range (0–1000 m) and with high resolution is studied to enhance a geometrical form factor. Theoretical modeling of Mie scattering echo signals agrees with the experimental results. Introduction of a lens in front of the detector is effective for increasing the geometrical form factor, and a significant improvement in the received signal intensity is achieved, especially for short-range measurements around 100 m. This is useful for the IR-lidar system with a detector diameter of less than 1 mm. In the theoretical model, a ray-tracing technique was applied and a transmitting laser beam with Gaussian profile was considered for better accuracy.     

直升机目标被动声跟踪算法及其仿真研究

本文提出了包含多普勒和声传播时间延迟的接收信号模型;提出了在直升机目标做匀速直线运动的条件下,将声基阵获得的测向信息与多普勒频移信息融合,估计目标运动参数的算法,并用蒙特卡罗方法分析了该算法的估计精度;仿真结果表明该算法可实现较高的估计精度,测距精度满足实用要求;最后研究了应用该算法的自适应跟踪问题．