In order to improve the interpretation of the earth system microwave remote sensing, the research of microwave spectrum characteristics of the ground truth (earth objects) was carried out in laboratory. A laboratory f...In order to improve the interpretation of the earth system microwave remote sensing, the research of microwave spectrum characteristics of the ground truth (earth objects) was carried out in laboratory. A laboratory for microwave remote sensing of the earth objects has been constructed to improve the remote sensing level, the laboratory consists of four parts: the measuring system of dielectric constants, the microwave emissivity meter, the microwave reflectometer and the microwave remote sensing simulation experiment in field. In this paper, the principle of measurement, the correction of near field process, the structure of instrument, the calibration method and the measurement of the earth substances, including soil, water and oil, are discussed. The labora- tory may supply the condition for measuring the parameters of thc earth substance remote sensing and help to interpret the remote sensing data.展开更多
The cordierite-ferrites based infrared radiation composite materials were synthesized with Fe2O3, Mn O2, Cu O, Co2O3, and Mg2Al4Si5O18 powders as raw materials via microwave heating. The cordierite-ferrites based comp...The cordierite-ferrites based infrared radiation composite materials were synthesized with Fe2O3, Mn O2, Cu O, Co2O3, and Mg2Al4Si5O18 powders as raw materials via microwave heating. The cordierite-ferrites based composite ceramics could be obtained via microwave heating at 1173 K for 1 h or 1473 K for 10 min, respectively. The lower synthesis temperature or the shorter heating time results in the smaller grain size of the composite ceramics obtained by microwave heating. The interplanar distance of cordierite becomes greater after microwave heating, indicating that the doping effect of transitional metal oxides on the cordierite is more efficient in microwave heating. The infrared radiation composite ceramics synthesized by microwave heating at 1473 K for 1 h exhibit the maximum emissivity of 0.9 in the band range of 6-8 μm at 1073 K.展开更多
A visible transparent metamaterial absorber was designed and fabricated with ultrabroadband microwave absorption and low infrared emissivity to meet the increasing demand for multispectral compatible camouflage. The a...A visible transparent metamaterial absorber was designed and fabricated with ultrabroadband microwave absorption and low infrared emissivity to meet the increasing demand for multispectral compatible camouflage. The absorber was fabricated with a low-infrared emissive layer at the top, a microwave-absorbing layer in the middle, and a reflective layer at the bottom, which were separated by polymethyl methacrylate plates. The absorber showed an average visible transmittance of 55%, infrared emissivity of ~0.37, and effective microwave absorption bandwidth of 32.1 GHz with a total thickness of 3.0 mm. Furthermore,microwave absorption exhibited wide-angle stability and polarization insensitivity characteristics. The mechanism of microwave attenuation was further explored through effective electromagnetic parameters as well as surface current, electric field, magnetic field, and energy loss density distributions. The experimental results were consistent with those of the simulations and calculations, indicating the potential of the designed metamaterial absorber for future applications in multispectral compatible camouflage.展开更多
Microwave Land Surface Emissivity(MLSE)over China under both clear and cloudy sky conditions was retrieved using measurements of recalibrated microwave brightness temperatures(Tbs)from Fengyun-3B Microwave Radiation I...Microwave Land Surface Emissivity(MLSE)over China under both clear and cloudy sky conditions was retrieved using measurements of recalibrated microwave brightness temperatures(Tbs)from Fengyun-3B Microwave Radiation Imager(FY-3B MWRI),combined with cloud properties derived from Himawari-8 Advanced Himawari Imager(AHI)observations.The contributions from cloud particles and atmospheric gases to the upwelling Tbs at the top of atmosphere were calculated and removed in radiative transfer.The MLSEs at horizontal polarizations at 10.65,18.7,and 36.5 GHz during 7 July 2015 to 30 June 2019 over China showed high values in the southeast vegetated area and low values in the northwest barren,or sparsely vegetated,area.The maximum values were found in the belt area of the Qinling-Taihang Mountains and the eastern edge of the Qinghai-Tibet Plateau,which is highly consistent with MLSEs derived from AMSR-E.It demonstrates that the measurements of FY-3B MWRI Tbs,including its calibration and validation,are reliable,and the retrieval algorithm developed in this study works well.Seasonal variations of MLSE in China are mainly driven by the combined effects of vegetation,rainfall,and snow cover.In tropical and southern forest regions,the seasonal variation of MLSE is small due to the enhancement from vegetation and the suppression from rainfall.In the boreal area,snow causes a significant decrease of MLSE at 36.5 GHz in winter.Meanwhile,the MLSE at lower frequencies experiences less suppression.In the desert region in Xinjiang,increases of MLSEs at all frequencies are observed with increasing snow cover.展开更多
When sea surface wavelengths are not larger than microwave wavelengths,the microwave emissivity of Gaussian rough sea surfaces can be investigated by applying effective media theory(EMT)of rough surfaces.For one-dimen...When sea surface wavelengths are not larger than microwave wavelengths,the microwave emissivity of Gaussian rough sea surfaces can be investigated by applying effective media theory(EMT)of rough surfaces.For one-dimensional Gaussian sea surface,the microwave emissivity model is proposed by EMT,which regards the air-sea rough interface as a new effective medium of isotropic permittivity between the top layer of air and the bottom layer of seawater.The emissivity model is controlled by the root mean square deviation(RMSD)of the rough surface height and the correlation length of the rough surface.Results clearly show that the emissivity increases along with the RMSD increase if the latter is smaller than a critical value.Furthermore,excess emissivities and the brightness temperature increments for a wind-roughened sea surface can be estimated from those of flat surfaces by fitting the RMSD as a function of wind speed.Good agreements are obtained by comparing the results of our model with the satellite data at microwave frequencies of 1.4,6.8,18,21,and 37 GHz,respectively.Moreover,these findings imply that our method can be extended to retrieve the sea surface parameters,such as RMSD and the correlation length of the rough surface,from the satellite data.展开更多
基于周期性阵列角锥结构星载微波辐射热定标源,运用时域有限差分算法(Finite Difference Time Domain,FDTD),建立有限大辐射体电磁波散射模型,探索该结构下热定标源在6.3～230 GHz内辐射特性变化趋势,分析热定标源辐射性能(包括反射率r...基于周期性阵列角锥结构星载微波辐射热定标源,运用时域有限差分算法(Finite Difference Time Domain,FDTD),建立有限大辐射体电磁波散射模型,探索该结构下热定标源在6.3～230 GHz内辐射特性变化趋势,分析热定标源辐射性能(包括反射率r和发射率e)随涂层厚度t、角锥高宽比以及角锥宽度p的变化规律。研究结果表明:热定标源反射率在低频段主要依赖涂层吸波性能,高频段则主要取决于涂层界面反射率;在低频段内,随涂层厚度的增加,热定标源反射率逐渐减小,发射率有所增大,但在高频处,呈现出较快的震荡趋势;在特定涂层厚度下,随着角锥高宽比增加,热定标源在全工作频段内反射率减小,发射率增大,且随着角锥宽度的增加,反射率增大,发射率减小。综合热定标源辐射性能研究结果,结合型号产品具体应用需求,设计开发出热定标源产品,并进行发射率测量,实测发射率均为0.998。展开更多
基金Supported by National Natural Science Foundation of China
文摘In order to improve the interpretation of the earth system microwave remote sensing, the research of microwave spectrum characteristics of the ground truth (earth objects) was carried out in laboratory. A laboratory for microwave remote sensing of the earth objects has been constructed to improve the remote sensing level, the laboratory consists of four parts: the measuring system of dielectric constants, the microwave emissivity meter, the microwave reflectometer and the microwave remote sensing simulation experiment in field. In this paper, the principle of measurement, the correction of near field process, the structure of instrument, the calibration method and the measurement of the earth substances, including soil, water and oil, are discussed. The labora- tory may supply the condition for measuring the parameters of thc earth substance remote sensing and help to interpret the remote sensing data.
基金financially supported by the National Natural Science Foundation of China (No. 11074195)Technology Innovation Fund of Jiangsu Province (No. SBC201310656)Technology Innovation Fund of Zhangjiagang City (No. ZKC1205)
文摘The cordierite-ferrites based infrared radiation composite materials were synthesized with Fe2O3, Mn O2, Cu O, Co2O3, and Mg2Al4Si5O18 powders as raw materials via microwave heating. The cordierite-ferrites based composite ceramics could be obtained via microwave heating at 1173 K for 1 h or 1473 K for 10 min, respectively. The lower synthesis temperature or the shorter heating time results in the smaller grain size of the composite ceramics obtained by microwave heating. The interplanar distance of cordierite becomes greater after microwave heating, indicating that the doping effect of transitional metal oxides on the cordierite is more efficient in microwave heating. The infrared radiation composite ceramics synthesized by microwave heating at 1473 K for 1 h exhibit the maximum emissivity of 0.9 in the band range of 6-8 μm at 1073 K.
文摘A visible transparent metamaterial absorber was designed and fabricated with ultrabroadband microwave absorption and low infrared emissivity to meet the increasing demand for multispectral compatible camouflage. The absorber was fabricated with a low-infrared emissive layer at the top, a microwave-absorbing layer in the middle, and a reflective layer at the bottom, which were separated by polymethyl methacrylate plates. The absorber showed an average visible transmittance of 55%, infrared emissivity of ~0.37, and effective microwave absorption bandwidth of 32.1 GHz with a total thickness of 3.0 mm. Furthermore,microwave absorption exhibited wide-angle stability and polarization insensitivity characteristics. The mechanism of microwave attenuation was further explored through effective electromagnetic parameters as well as surface current, electric field, magnetic field, and energy loss density distributions. The experimental results were consistent with those of the simulations and calculations, indicating the potential of the designed metamaterial absorber for future applications in multispectral compatible camouflage.
基金the National Natural Science Foundation of China(Grant Nos.41830104,41661144007,41675022,and 41375148)Research and Development Program of China(Grant No.2017YFC1501402)the Jiangsu Provincial 2011 Program(Col-laborative Innovation Center of Climate Change).
文摘Microwave Land Surface Emissivity(MLSE)over China under both clear and cloudy sky conditions was retrieved using measurements of recalibrated microwave brightness temperatures(Tbs)from Fengyun-3B Microwave Radiation Imager(FY-3B MWRI),combined with cloud properties derived from Himawari-8 Advanced Himawari Imager(AHI)observations.The contributions from cloud particles and atmospheric gases to the upwelling Tbs at the top of atmosphere were calculated and removed in radiative transfer.The MLSEs at horizontal polarizations at 10.65,18.7,and 36.5 GHz during 7 July 2015 to 30 June 2019 over China showed high values in the southeast vegetated area and low values in the northwest barren,or sparsely vegetated,area.The maximum values were found in the belt area of the Qinling-Taihang Mountains and the eastern edge of the Qinghai-Tibet Plateau,which is highly consistent with MLSEs derived from AMSR-E.It demonstrates that the measurements of FY-3B MWRI Tbs,including its calibration and validation,are reliable,and the retrieval algorithm developed in this study works well.Seasonal variations of MLSE in China are mainly driven by the combined effects of vegetation,rainfall,and snow cover.In tropical and southern forest regions,the seasonal variation of MLSE is small due to the enhancement from vegetation and the suppression from rainfall.In the boreal area,snow causes a significant decrease of MLSE at 36.5 GHz in winter.Meanwhile,the MLSE at lower frequencies experiences less suppression.In the desert region in Xinjiang,increases of MLSEs at all frequencies are observed with increasing snow cover.
基金supported by the National Natural Science Foundation of China(No.41676169)the National Key R&D Program of China(No.2016YFC1401006).
文摘When sea surface wavelengths are not larger than microwave wavelengths,the microwave emissivity of Gaussian rough sea surfaces can be investigated by applying effective media theory(EMT)of rough surfaces.For one-dimensional Gaussian sea surface,the microwave emissivity model is proposed by EMT,which regards the air-sea rough interface as a new effective medium of isotropic permittivity between the top layer of air and the bottom layer of seawater.The emissivity model is controlled by the root mean square deviation(RMSD)of the rough surface height and the correlation length of the rough surface.Results clearly show that the emissivity increases along with the RMSD increase if the latter is smaller than a critical value.Furthermore,excess emissivities and the brightness temperature increments for a wind-roughened sea surface can be estimated from those of flat surfaces by fitting the RMSD as a function of wind speed.Good agreements are obtained by comparing the results of our model with the satellite data at microwave frequencies of 1.4,6.8,18,21,and 37 GHz,respectively.Moreover,these findings imply that our method can be extended to retrieve the sea surface parameters,such as RMSD and the correlation length of the rough surface,from the satellite data.
文摘基于周期性阵列角锥结构星载微波辐射热定标源,运用时域有限差分算法(Finite Difference Time Domain,FDTD),建立有限大辐射体电磁波散射模型,探索该结构下热定标源在6.3～230 GHz内辐射特性变化趋势,分析热定标源辐射性能(包括反射率r和发射率e)随涂层厚度t、角锥高宽比以及角锥宽度p的变化规律。研究结果表明:热定标源反射率在低频段主要依赖涂层吸波性能,高频段则主要取决于涂层界面反射率;在低频段内,随涂层厚度的增加,热定标源反射率逐渐减小,发射率有所增大,但在高频处,呈现出较快的震荡趋势;在特定涂层厚度下,随着角锥高宽比增加,热定标源在全工作频段内反射率减小,发射率增大,且随着角锥宽度的增加,反射率增大,发射率减小。综合热定标源辐射性能研究结果,结合型号产品具体应用需求,设计开发出热定标源产品,并进行发射率测量,实测发射率均为0.998。
