近距微波热辐射的拟量子过程建模方法

Thermal radiation is the phenomenon of spontaneous emission of non-coherent electromagnetic waves due to the existence of temperature. The thermal radiation intensity of the object, namely the brightness temperature, is mainly determined by the physical temperature and material properties. Therefore, physical parameters of terrains can be detected by measuring the brightness temperature from the widely used space-borne passive microwave remote sensors. In far fields, the theoretical link from target emissivity, radiation transmission and antenna reception has been completed and consistently being improved, which effectively supports the passive microwave remote sensing observations. However, the radiometer calibration process which is significant for the quantitative passive microwave remote sensing, is typically applied in the short-range, and suffers from the in-completed analytical theory system of short range radiation receiving. As a result, the radiometer calibration technology is not sufficient to meet the future demands by remote observations to achieve a higher accuracy. This project intends to carry out studies on the two remaining and significant scientific issues in the short-range radiation detection, namely, the short-range radiation characteristics from complex targets, and the receiving characteristics of the partially coherent radiation fields by the coherent antenna. A non-coherent signal model based on the quasi-quantum process concept is to be established and then applied with a full wave time-domain numerical algorithm. The methodology of modeling face and body radiation source are to be investigated to construct an arbitrary shape target, then the short-range radiation from which will be studied, including partial coherence, brightness temperature distribution and so forth. By both manners of numerical simulations and theoretical derivation, the applicant is to research on the method of obtaining the antenna received radiation power by means of coupling integration between partially coherent radiation fields and coherent antenna aperture fields. This project can contribute to the theoretical system of short-range microwave radiation detection, and provide with analytical methodologies for the radiometer calibration tasks and other near-field microwave radiation measurement applications.

热辐射是物体由于温度的存在自发发射非相干电磁波的现象。物体热辐射强度，即亮温主要由物理温度和材质属性决定，可通过探测地物的亮温反演其物理参数，如广泛应用的星载被动微波遥感器。远场条件下，目标发射率、辐射传输、天线接收的全链路探测理论已趋于完善，有效支撑着被动微波遥感的观测体系。然而，定量被动微波遥感所依赖的辐射计定标实为近距辐射测量过程，受到理论体系不完整的制约，难以应对未来更高精度的观测需求。本项目拟针对其中复杂目标近距辐射特性、部分相干场-天线相干接收特性两大科学问题开展研究。基于拟量子过程非相干源时域信号模型的建立与全波时域数值算法，研究任意形貌目标辐射面源和辐射体源的建模方法，分析其近距辐射特性如部分相干性，亮温分布等；结合仿真和理论，研究等效近距天线接收的部分相干辐射场-天线相干场的耦合积分方法，完善近距微波辐射测量理论体系，为辐射计定标技术及其他近场辐射测量研究提供方法支撑。

本项目研究微波辐射计定标过程中的建模方法和机理问题，主要针对定标源向近距接收天线的热辐射传递过程开展正向建模方法研究。项目以构建拟量子过程的热辐射激励信号为起点，基于电磁场全波数值方法，通过在辐射体内密布非相干热辐射源，直接建立包含定标源结构、热辐射电磁波传播、和天线接收的仿真场景，分析从源到天线端口的热辐射传递过程。同时，项目也针对定标链路的源头-微波黑体定标源开展研究，针对近年来定标源国产化和发射率性能测定需求。.通过项目研究，实现了从复杂结构热源到接收天线的热辐射传递模拟，同时数值分析结果表明，定标源和近距天线之间的近场效应，包括定标源本身热辐射的近场非均匀性，和辐射电磁波在天线和定标源结构间的反射效应，会对亮温传递过程引入一定扰动，这一现象需要在实际定标链路设计和应用中予以考虑。除了密布热源的直接建模仿真路径，项目还探索了逐点激励的建模方式，可以明确局部热源对天线端口接收功率的相对贡献，是后续实现定标链路高精度建模分析的重要基础。此外，项目围绕微波黑体定标源取得的研究进展包括：以定向亮温辐射性能为评价依据进一步推进了定标源优化设计；通过定标源散射机理的系统性分析进一步完善了定标源发射率的测定方法体系。此方面的研究进展在我国航空航天辐射计定标系统的研制和保障方面具备直接的应用价值。.总体而言，本项目围绕微波辐射计定标中的理论问题取得进展，可以定性地分析源到天线接收过程中的趋势性现象。面向我国被动微波遥感观测体系的高精度定量化发展需求，和后续实现定标链路高精度建模与系统性提升定标精度的具体目标，本项目的研究进展可作为重要的方法和机理基础。