With appropriate geometry configuration, helicopter- borne rotating synthetic aperture radar （ROSAR） can break through the limitations of monostatic synthetic aperture radar （SAR） on forward-looking imaging. With ...With appropriate geometry configuration, helicopter- borne rotating synthetic aperture radar （ROSAR） can break through the limitations of monostatic synthetic aperture radar （SAR） on forward-looking imaging. With this capability, ROSAR has extensive potential applications, such as self-navigation and self-landing. Moreover, it has many advantages if combined with the frequency modulated continuous wave （FMCW） technology. A novel geometric configuration and an imaging algorithm for helicopter-borne FMCW-ROSAR are proposed. Firstly, by per- forming the equivalent phase center principle, the separated trans- mitting and receiving antenna system is equalized to the case of system configuration with antenna for both transmitting and receiving signals. Based on this, the accurate two-dimensional spectrum is obtained and the Doppler frequency shift effect in- duced by the continuous motion of the platform during the long pulse duration is compensated. Next, the impacts of the velocity approximation error on the imaging algorithm are analyzed in de- tail, and the system parameters selection and resolution analysis are presented. The well-focused SAR image is then obtained by using the improved Omega-K algorithm incorporating the accurate compensation method for the velocity approximation error. FJnally, correctness of the analysis and effectiveness of the proposed al- gorithm are demonstrated through simulation results.展开更多
In ship-borne radar, because of the influence of interference factors such as the correlation of background array noise and the coherence of targets and so on, the performance of high-resolution algorithms such as MUS...In ship-borne radar, because of the influence of interference factors such as the correlation of background array noise and the coherence of targets and so on, the performance of high-resolution algorithms such as MUSIC is degraded. In this document by pre-whitening of background array color noise, de-correlation of coherent targets, compensation of amplitude-phase mismatch, pre-whitened-constrained-MUSIC algorithm in ship-borne radar effectively resolutes ship target and first-order sea echo. Furthermore, the algorithm performance is compared with other algorithms, result shows that pre-whitened-constrained-MUSIC can be applied effectively in high-resolution processing in ship-borne radar.展开更多
A new Suboptimal Maximum Likelihood Estimation (SMLE) algorithm based on full-deramp model and its implementation in satellite-borne radar altimeter are presented, with emphasis on the influence of both the return flu...A new Suboptimal Maximum Likelihood Estimation (SMLE) algorithm based on full-deramp model and its implementation in satellite-borne radar altimeter are presented, with emphasis on the influence of both the return fluctuation and the receiver noise on height and slope estimation precision. Some conclusions are obtained and verified by computer simulation.展开更多
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...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。展开更多
A retrieval method of microwave(MW)space-borne remote sensing of cloud liquid water content by the combined radar-radiometer is suggested.A three-layer cloud model is chosen to represent the typical stratified precipi...A retrieval method of microwave(MW)space-borne remote sensing of cloud liquid water content by the combined radar-radiometer is suggested.A three-layer cloud model is chosen to represent the typical stratified precipitating cloud.The retrieval method mainly follows our previously suggested scheme with some modifications.Numerical comparative study shows that in space-borne remote sensing of cloud liquid water content by the combined method is much better than by radar only;Also the retrieval accuracy of cloud liquid water content may be improved when using the three-layer cloud model in the combined method.展开更多
使用热带测雨卫星(TRMM)搭载的测雨雷达(PR)2004—2014年长达11a的连续观测资料对青藏高原东南缘川渝地区不同季节不同降水类型的垂直结构特征进行了统计分析,并建立了相应的气候态反射率垂直廓线(Vertical Profiles of Reflectivity,简...使用热带测雨卫星(TRMM)搭载的测雨雷达(PR)2004—2014年长达11a的连续观测资料对青藏高原东南缘川渝地区不同季节不同降水类型的垂直结构特征进行了统计分析,并建立了相应的气候态反射率垂直廓线(Vertical Profiles of Reflectivity,简称VPR)。结果表明,由于不同的微物理及动力过程,降水类型对反射率垂直廓线的结构特征影响很大,90%的层云0℃层亮带峰值强度低于32dBz,50%的对流云最大反射率强度超过35dBz。降水类型及强度均对反射率垂直廓线的形状影响很大,层云系统发生中及大雨时其冰雪区的聚合反应效率明显较发生小雨时高。反射率垂直廓线特征参数具有一定的区域性和季节特征,且地表加热和地形高度的作用会加强上升气流对反射率垂直廓线形态的影响,上升气流的强度影响着冰雪及雨水区的碰并增长率以及低层的蒸发作用,从而进一步影响低层雨区的反射率垂直廓线斜率,边界层的相对湿度是另一个影响雨区反射率垂直廓线斜率及蒸发率的重要因素。星载测雨雷达的云分类算法在青藏高原东南缘地区受到一定的挑战,仍有改进的空间;未来可以将基于星载测雨雷达建立气候态层云典型反射率垂直廓线应用于联合地基天气雷达网观测以弥补后者在复杂地形条件下探测范围及能力受限的缺陷,从而改进雷达定量降水估测的误差。展开更多
基金supported by the National Basic Research Program of China(2011CB707001)the Fundamental Research Funds for the Central Universities(106112015CDJXY500001CDJZR165505)
文摘With appropriate geometry configuration, helicopter- borne rotating synthetic aperture radar （ROSAR） can break through the limitations of monostatic synthetic aperture radar （SAR） on forward-looking imaging. With this capability, ROSAR has extensive potential applications, such as self-navigation and self-landing. Moreover, it has many advantages if combined with the frequency modulated continuous wave （FMCW） technology. A novel geometric configuration and an imaging algorithm for helicopter-borne FMCW-ROSAR are proposed. Firstly, by per- forming the equivalent phase center principle, the separated trans- mitting and receiving antenna system is equalized to the case of system configuration with antenna for both transmitting and receiving signals. Based on this, the accurate two-dimensional spectrum is obtained and the Doppler frequency shift effect in- duced by the continuous motion of the platform during the long pulse duration is compensated. Next, the impacts of the velocity approximation error on the imaging algorithm are analyzed in de- tail, and the system parameters selection and resolution analysis are presented. The well-focused SAR image is then obtained by using the improved Omega-K algorithm incorporating the accurate compensation method for the velocity approximation error. FJnally, correctness of the analysis and effectiveness of the proposed al- gorithm are demonstrated through simulation results.
文摘In ship-borne radar, because of the influence of interference factors such as the correlation of background array noise and the coherence of targets and so on, the performance of high-resolution algorithms such as MUSIC is degraded. In this document by pre-whitening of background array color noise, de-correlation of coherent targets, compensation of amplitude-phase mismatch, pre-whitened-constrained-MUSIC algorithm in ship-borne radar effectively resolutes ship target and first-order sea echo. Furthermore, the algorithm performance is compared with other algorithms, result shows that pre-whitened-constrained-MUSIC can be applied effectively in high-resolution processing in ship-borne radar.
文摘A new Suboptimal Maximum Likelihood Estimation (SMLE) algorithm based on full-deramp model and its implementation in satellite-borne radar altimeter are presented, with emphasis on the influence of both the return fluctuation and the receiver noise on height and slope estimation precision. Some conclusions are obtained and verified by computer simulation.
文摘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。
基金This work is sponsored by the National Natural Science Foundation of China under the auspices of Project Contrant No.49485006.
文摘A retrieval method of microwave(MW)space-borne remote sensing of cloud liquid water content by the combined radar-radiometer is suggested.A three-layer cloud model is chosen to represent the typical stratified precipitating cloud.The retrieval method mainly follows our previously suggested scheme with some modifications.Numerical comparative study shows that in space-borne remote sensing of cloud liquid water content by the combined method is much better than by radar only;Also the retrieval accuracy of cloud liquid water content may be improved when using the three-layer cloud model in the combined method.
文摘使用热带测雨卫星(TRMM)搭载的测雨雷达(PR)2004—2014年长达11a的连续观测资料对青藏高原东南缘川渝地区不同季节不同降水类型的垂直结构特征进行了统计分析,并建立了相应的气候态反射率垂直廓线(Vertical Profiles of Reflectivity,简称VPR)。结果表明,由于不同的微物理及动力过程,降水类型对反射率垂直廓线的结构特征影响很大,90%的层云0℃层亮带峰值强度低于32dBz,50%的对流云最大反射率强度超过35dBz。降水类型及强度均对反射率垂直廓线的形状影响很大,层云系统发生中及大雨时其冰雪区的聚合反应效率明显较发生小雨时高。反射率垂直廓线特征参数具有一定的区域性和季节特征,且地表加热和地形高度的作用会加强上升气流对反射率垂直廓线形态的影响,上升气流的强度影响着冰雪及雨水区的碰并增长率以及低层的蒸发作用,从而进一步影响低层雨区的反射率垂直廓线斜率,边界层的相对湿度是另一个影响雨区反射率垂直廓线斜率及蒸发率的重要因素。星载测雨雷达的云分类算法在青藏高原东南缘地区受到一定的挑战,仍有改进的空间;未来可以将基于星载测雨雷达建立气候态层云典型反射率垂直廓线应用于联合地基天气雷达网观测以弥补后者在复杂地形条件下探测范围及能力受限的缺陷,从而改进雷达定量降水估测的误差。
