综合孔径微波辐射计天线单元互耦的影响及其校正

本文建立了综合孔径微波辐射计天线单元之间互耦对于综合孔径成像的影响的模型,分析了天线单元之间的互耦对于综合孔径微波辐射计分辨率的影响.给出了校正天线单元互耦作用影响的方法,在此基础上提出了一种综合孔径微波辐射计的定标方法.通过数值模拟,证明了所提出的方法的有效性.     

Interferometric synthetic aperture microwave radiometry for theremote sensing of the Earth

Interferometric aperture synthesis is presented as an alternative to real aperture measurements of the Earth's brightness temperature from low Earth orbit. The signal-to-noise performance of a single interferometric measurement is considered, and the noise characteristics of the brightness temperature image produced from the interferometer measurements are discussed. The sampling requirements of the measurements and the resulting effects of the noise in the measurements on the image are described. The specific case of the electronically steered thinned array radiometer (ESTAR) currently under construction is examined. The ESTAR prototype is described in detail sufficient to permit a performance evaluation of its spatial and temperature resolution. Critical aspects of an extension of the ESTAR sensor to a larger spaceborne system are considered. Of particular important are the number and placement of antenna elements in the imaging array     

综合孔径微波辐射计顺轨方向亮温反演算法的研究

本文利用卷积理论对综合孔径微波辐射计在顺轨方向的孔径综合进行了理论分析,给出了在一定条件下的基线设计,并且分别利用矩量法和基于Backus-Gilbert理论的线性算法两种数值方法进行了顺轨方向地物亮温的反演.数值模拟结果表明,在顺轨方向有效稀疏天线阵设计的基础上,亮温反演达到了很高的精度.     

The impact of antenna pattern frequency dependence in aperture synthesis microwave radiometers

The effect of the frequency dependence of the antenna voltage patterns within the bandwidth of an aperture synthesis interferometric radiometer is studied and quantified using actual antenna voltage patterns measured at different frequencies for the first nine receivers of the Microwave Imaging Radiometer with Aperture Synthesis instrument aboard the European Space Agency's Soil Moisture and Ocean Salinity mission. A technique is proposed to mitigate this effect.     

Sun effects in 2-D aperture synthesis radiometry imaging and their cancelation

The Microwave Imaging Radiometer by Aperture Synthesis (MIRAS) is the single payload of the European Space Agency's (ESA) Soil Moisture and Ocean Salinity (SMOS) Earth Explorer Opportunity mission. MIRAS will be the first two-dimensional aperture synthesis radiometer for Earth observation. Two-dimensional aperture synthesis radiometers can generate brightness temperature images by a Fourier synthesis process without mechanical antenna steering. To do so and have the necessary wide swath for Earth observation, the array is formed by small and low directive antennas, which do not attenuate enough bright noise sources that may interfere with the measurements. This study analyzes the impact of the radio-frequency emission from the Sun in the SMOS mission, reviews the basic image reconstruction algorithms, and proposes a technique to minimize Sun effects.     

二维综合孔径微波辐射计圆环结构天线阵 及其稀疏方法

本文介绍了圆环天线阵二维综合孔径微波辐射计的测量原理和反演算法,并通过模拟退火算法讨论了两种二维综合孔径微波辐射计圆环阵的稀疏方案,一种方案利用天线旋转,在半圆周上稀疏天线;另一种方案通过将空间频率采样点的均匀分布作为优化的约束条件,在全圆周上稀疏天线.结果显示两种设计较传统设计均有改进之处.对于半圆周天线而言,在积分时间允许的条件下,通过天线旋转与分时测量,天线阵可进一步稀疏.对于全圆周天线而言,与Y形天线阵结构相比,在同样的空间频率覆盖范围内,全圆周天线阵使天线单元数达到了最优.     

基于压缩感知的下视三维SAR成像新方法

下视3维合成孔径雷达(Synthetic Aperture Radar, SAR)可对平台正下方目标进行3维重构,具有广阔的应用前景。为有效减少线阵天线所需阵元数,该文提出了一种基于稀疏阵列的下视3维SAR成像方法。为了抑制稀疏阵列导致的栅瓣效应,该方法结合压缩感知(Compressed Sensing, CS)理论,实现对下方3维目标的成像。分析了稀疏阵列配置对稀疏信号处理的影响以及3维成像采用稀疏信号处理的可行性。最后通过仿真实验验证了该文分析的正确性及算法的有效性。     

Imaging Simulation for MMW Synthetic Aperture Radiometer

A synthetic aperture radiometer is a new type of passive remote sensing instrument that can reach high spatial resolution. Restricted by antenna element size and operating wavelength, however, the system design is difficult at MMW band. In this paper, main technical parameters optimization of a synthetic aperture radiometer is discussed. Based on low-redundancy linear arrays, a millimeter wave synthetic aperture radiometric imaging scheme is presented. The simulation experimental results show that the system imaging effect depends on the synthetic aperture antenna pattern.     

ESTAR: a synthetic aperture microwave radiometer for remote sensingapplications

ESTAR represents a new technology being developed for passive microwave remote sensing of the environment from space. The instrument employs an interferometric technique called aperture synthesis in which the coherent product from pairs of antennas is measured as a function of pair spacing. Substantial reductions in the antenna aperture needed for a given spatial resolution can be achieved with this technique. As a result, aperture synthesis could lead to practical passive microwave remote sensing instruments in space to measure parameters such as soil moisture and ocean salinity which require observations at long wavelengths and, therefore, large antennas. ESTAR is an L-band, aircraft built as part of research to develop this technique ESTAR is a hybrid real-and-synthetic aperture radiometer which employs stick antennas to achieve resolution along track and uses aperture synthesis to achieve resolution across track. Experiments to validate the instrument's ability to measure soil moisture have recently been conducted at the USDA watersheds at Walnut Gulch in Arizona and the Little Washita River in Oklahoma. The results of both experiments indicate that a valid image reconstruction and calibration have been obtained for this remote sensing technique     

干涉合成孔径辐射计的相位误差分析

干涉合成孔径辐射计是一种被动成像手段,可以根据目标和背景的亮温差别,实现目标探测功能,在揭露伪装、发现隐蔽目标方面有应用价值。介绍了干涉综合孔径辐射计成像基本原理,给出了一种毫米波干涉综合孔径成像系统的系统结构,分析了通道间相位误差对其性能的影响,设计了消除相位误差的校准方案,并对校准方案进行了仿真分析。     

Ka波段毫米波综合孔径辐射计成像研究

华中科技大学电磁场与微波技术中心已经设计并研制出一套工作于Ka波段的16阵元一维毫米波综合孔径辐射成像系统HUST-ASR,样机采用了最小冗余稀疏直线阵列以及先进的数字相关技术。阵列幅相误差对综合孔径辐射计成像会产生严重影响,文中提出一种不增加系统硬件复杂度、易于实现的单外部辅助源校正方法,给出在辐射计低信噪比条件下的校正算法,并进行了成像试验验证。试验结果表明,该校正方法能够有效校正毫米波综合孔径辐射计的幅相误差,经过校正后的成像系统对自然场景实现了非常清晰的毫米波综合孔径亮温图像,空间分辨率达到0.64°,证明该系统具有良好的成像性能。     

New Model for Synthesis of Symmetrical Thinned Linear Arrays

In symmetrical thinned linear arrays design, the positions of thinned array elements are very important for optimal performance in terms of its minimum peak side lobe level （Msli）. For the synthesis of thinned arrays with a given thinning rate, it would have almost the same Msll solution between taking only segmental aperture nearby both ends of the aperture into account and taking all the aperture into account. In this paper, the element distribution characteristic over the aperture of many optimum thinned arrays is studied, then the aperture release model is founded by the least square method to synthesize the thinned arrays. This model is vital for the computing burden alleviation and the efficiency optimization, and would hardly bring any degradation of the obtained array performance.     

New Model for Synthesis of Symmetrical Thinned Linear Arrays

In symmetrical thinned linear arrays design, the positions of thinned array elements are very important for optimal performance in terms of its minimum peak side lobe level (Msll). For the synthesis of thinned arrays with a given thinning rate, it would have almost the same Msll solution between taking only segmental aperture nearby both ends of the aperture into account and taking all the aperture into account. In this paper, the element distribution characteristic over the aperture of many optimum thinned arrays is studied, then the aperture release model is founded by the least square method to synthesize the thinned arrays. This model is vital for the computing burden alleviation and the efficiency optimization, and would hardly bring any degradation of the obtained array performance.     

Aperture synthesis concepts in microwave remote sensing of theEarth

The application of aperture synthesis concepts, used for many years in radioastronomy to achieve high image resolution at a reasonable cost, to remote sensing technology is discussed. The electronically scanned thinned array radiometer (ESTAR) is put forward as a viable alternative to improve spatial resolution by an order of magnitude over what is presently achieved by microwave imaging systems that are collecting data from Earth orbit. Future developments in airborne sensor technology and potential spacecraft application are described     

综合孔径微波辐射计成像观测能力

对综合孔径微波辐射计成像观测原理进行了阐述,分析了综合孔径微波辐射计的灵敏度、积分时间、天线波束宽度、目标亮温、背景噪声温度、系统工作频率和目标等效截面等因素与系统作用距离的关系,对系统的目标观测能力进行仿真验证,探讨了阵列通道不一致等误差的补偿方法。研究成果将有助于综合孔径微波辐射计的实用化推进。     

基于多通道重构的DPCA SAR方位向信号处理

研究了一种基于方位向相位中心偏移天线技术的机载合成孔径雷达(SAR)实现方法。通过在方位向上安置相位中心偏移的多个波束来降低系统对脉冲重复频率的要求,从而在保证方位向分辨率不变的条件下能够扩展机载SAR的测绘带宽。针对由脉冲重复频率的变化造成的方位信号非均匀采样,采用了多通道重构算法来恢复均匀采样信号,以两通道机载SAR为例,通过仿真实例验证了该算法的有效性。     

综合孔径微波辐射计光学实时信号处理系统

分析了综合孔径微波辐射计光学实时信号处理系统的基本原理及关键技术,研制了一套X波段6单元综合孔径红外实时信号处理系统样机,并进行了系统测试及点辐射源的一维实时成像实验,获得了清晰的干涉条纹图像.初步的实验结果验证了综合孔径辐射计光学实时信号处理的可行性及系统设计的正确性.     

基于NUFFT 算法的综合孔径辐射计图像反演方法

圆形阵列和旋转阵列排布方式的提出是为进一步降低综合孔径辐射计成像系统的复杂度和成本,然 而其缺陷在于过于复杂的亮温图像反演过程,因为该阵列排布方式下的采样样本不是均匀分布于整个采样平面,常 规的标准傅里叶变换不能直接运用于此反演过程。提出了一种非标准快速傅里叶变换(NUFFT)算法,用于非均匀 采样样本的综合孔径辐射计图像反演计算,该算法结合了高斯栅格算法和对过采样样本的快速傅里叶变换算法,仿 真结果表明该算法能够准确地得到反演图像。     

共享孔径同心圆阵稀疏交错优化布阵方法

同心圆阵列天线具有波束对称、360°方位角扫描、抗干扰能力强等优点，被广泛应用于星载、机载、舰载雷达及飞机声呐等领域。在天线孔径有限的情况下，如何进一步提高同心圆阵的孔径利用率，通过孔径的空分复用，设计出子阵稀疏交错分布的多功能同心圆阵列天线，具有较大的研究价值。利用均匀同心圆阵列天线激励与方向图函数存在二维傅里叶-贝塞尔变换关系，基于二维三次插值和密度加权，提出了一种同心圆阵稀疏交错优化布阵的方法。该方法通过对均匀同心圆阵列天线方向图采样值的频谱能量进行分析，采用三次插值的方法，实现了同心圆天线阵列方向图函数到同心圆阵元激励能量的映射转换；基于密度加权的原理，对排序后归一化阵元激励的奇偶交错选取，使得稀疏交错子阵方向图频谱能量均分匹配，实现了同心圆阵的稀疏交错优化布阵设计。仿真结果表明，该方法得到的交错子阵天线具有峰值旁瓣电平低、主瓣宽度窄且方向图性能近似程度高的优点，有效解决了同心圆阵列天线稀疏交错优化布阵的设计难题，实现了两子阵交错的共享孔径多功能同心圆阵列天线设计。