Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335
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Abstract:A miniaturization Ka-band direct detection receiver based on monolithic microwave integrated circuit(MMIC) used for passive millimeter wave(MMW) imaging was proposed. This receiver was composed of wideband low noise amplifiers (LNA) module, small signal diode detector and dc amplifier.Each module was designed,fabricated, and tested. The performance of the receiver was also tested.The measured results show that the receiver achieves a RF gain above 30dB with noise figure less than 3.8dB and an effective bandwidth 7.4GHz.Some MMW images obtained with this receiver using a horn antenna prove the receiver's applicability in passive MMW imaging.
Abstract:TiNx thin films were deposited on p-Si(111) substrate by DC magnetron reactive sputtering method . The composition, structure and photoelectric properties of the films were studied by using energy dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD), UV-visible spectrophotometer, and four-probe resistivity meter. The results show that the atomic ratio N/Ti of the prepared TiNx thin films is close to 1. The preferred orientation of TiNx thin films is obviously influenced by the substrate temperature, and there is a transition of the preferred orientation from (111) to (200) when the substrate temperature is about 240℃. The average reflectivity of films in the near infrared band first increase and then decrease with the increase of substrate temperature, while the resistivity of TiNx thin films decrease rapidly.
Abstract:Ferroelectric bismuth vanadate（B2VO5.5） thin films were successfully fabricated on n-type Si (100) substrate by sol-gel method. The microstructures of the films were investigated by X-ray diffraction and atomic force microscopy. The results indicated that B2VO5.5 thin films show a good match with the n-Si substrate and a high c-axis preferred orientation with a uniform grain distribution. The investigation on the electrical properties of B2VO5.5 thin films indicated that B2VO5.5 thin films show good capacitance-voltage characteristics, and the memory window was larger than 0.4 V with the gate voltage ±4 V. The leakage current density was about 5×10-8 Acm-2 when the applied voltage was 3.2 V. The dielectric constant and dielectric loss measured at 1 kHz were 95 and 0.22 respectively. All the results indicate that Bi2VO5.5 thin films have potential applications in ferroelectric memory devices.
Abstract:Based on the technology of monolayer Microbolometer, which used Si3N4 and SiO2 double-layer membrane supporting materials, the analytic expression of the normal stress and the thermal conductivity of the microbridge leg were derived by using the mechanical equivalent cross-secton methods and the composite thermal conductivity formula. The influence of the thickness ratio m of Si3N4 to SiO2 on the mechanical and thermal characteristic of microbridge was analyzed when other factors were not changed. At last, the theoretical derivation were verified by method of ANSYS finite element simulation.
Abstract:A low-cost and efficient parameter test system for infrared focal plane arrays(IRFPA)was introduced. The test bench including control module, blackbody, UFPA module, signal acquisition module and the host computer program was established and the critical technologies of this system were analyzed. This system can realize real-time signal acquisition, and at the same time it can be used to analyze some important parameters, such as root mean square noise,nonuniformity, responsivity, detectivity, noise equivalent power(NEP) and noise equivalent temperature difference(NETD), and so on. This system also can accurately determine the number and location of bad pixels, analyze, assess, and store the performances parameter of each good pixel of devices.
Abstract:Bi-material cantilever is an important element in a heat energy sensor for its thermal–mechanical character. The cantilever based on silicon process is usually made of metal and non-metal films. To improve the reliability of the cantilever, an adhesive layer is often needed between two films which do not adhere steadily each other. For analyzing bi-material structure with an adhesive layer in between, according to the theories of thermal stress and combined deformation on mechanics of materials, a tri-layer material cantilever model was set up related to the physics properties of materials, the structure dimension of cantilever, and the tilt angle caused by thermal stress. The material selection, the thickness, and the thickness ratio determination of a tri-material cantilever were analyzed by this model. Based on silicon process, an optic readout infrared focal plan array(IRFPA) was designed, fabricated, and tested. The results show that the model is practical and accurate enough. The model was also verified by a finite element simulation.
Abstract:The geometry, electronic structure and optical properties of purerutile-phase TiO2 and HfxTi1-xO2 formed by substituting Hf for Ti in TiO2 were studied by using the plane-wave ultra-soft pseudo-potential method based on the density functional theory. The calculations show that all the compounds of HfxTi1-xO2 are indirect band gap semiconductors. The values of band gap for HfxTi1-xO2 are bigger than that for pure TiO2. The static dielectric constant of HfxTi1-xO2 is smaller than that of pure TiO2 but larger than that of silicon dioxide.The results suggest that HfxTi1-xO2 can meet the requirement on high k materials in microelectronics industry.
Abstract:An infrared radiation model for high temperature ceramics under aerodynamic heating condition was developed by analyzing the relationship between the internal thermal radiation. the temperature field of heat transfer, as well as the reflection and refraction at surface. The control volume method combined with the Monte Carlo method and spectral model were used to simulate the radiation heat transfer in the ceramics and outgoing process. The medium effect factor was introduced to analyze the infrared radiation mechanism of the material and the effects of aerodynamic heating on the infrared characteristics. The results show that the coupling of spectral selectivity of thermal radiation inside the high temperature ceramics of the temperature field results in the dependence of material infrared emissivity on the heat flux of aerodynamic heating. The high temperature ceramics absorbs radiation in the ultraviolet, mid-infrared, and the far infrared intensively while absorbs radiation in visible spectra and near infrared weakly. So, the effective region inside the material, where the thermal radiation of medium can contribute to the infrared emission of the material surface, enlarges will the increase of aerodynamic heating, but the infrared emissivity of material decreases.
Abstract:A waveguide periodically loaded with lossy dielectric rings and metal rings is able to effectively control the attenuation to each mode, this is important for suppressing the absolute instability and enhancing the performance of a millimeter-wave gyrotron-traveling-wave amplifier (gyro-TWT). The modal mapping between the periodic waveguide and the uniform waveguide was systematically studied for a periodic ceramic-loaded cylindrical waveguide applied in TE01 mode gyro-TWT at Ka-band . It was revealed that, with a proper dielectric thickness, a higher order mode in uniform dielectric-loaded waveguide can be mapped to a lower order mode in smooth waveguide and the field distributions of the inter-mapped modes in vacuum region bear good resemblance to each other. A mode in periodic system exhibits complex mode distribution . In a period, the field distributions in the dielectric section and the metal ring section are mapped to those in uniform dielectric-loaded waveguide and smooth waveguide, respectively. The understanding of the modal mapping between the periodic dielectric-loaded waveguide and smooth waveguide is the precondition for the analysis of the complex electron cyclotron interaction in such a periodic system, which brings helpful guidance to the simplification of the physical model.
Abstract:A theoretical method for calculating the loss spectrum of the hollow fiber inner-coated with multi-dielectric-layer and silver layer was proposed. The transmission loss characteristics of infrared hollow fibers were analyzed theoretically. The film thickness for each dielectric layer was estimated according to the measured loss spectra by introducing the film thickness,material dispersion, and surface roughness into the theoretical calculation.The fabrication parameters of liquid-phase coating and iodization process for SiO2 and AgI film were adjusted by comparing the measured and the calculated loss spectra. A hollow fiber with Ag/SiO2/AgI/SiO2 structure was fabricated and low-loss property was demonstrated in the mid-infrared wavelength region.
Abstract:Laser induced breakdown spectroscopy (LIBS) is an elemental analysis technique, Its ultimate goal is to provide a highly quantitative analysis. Matrix correction method was put forward tocompensate for the deficiency of the traditional quantitative method. This method is effective in reducing the impact of matrix effect on the measurement results, The limitation of standard samples is relaxed, and the scopes of application are expanded. The feasibility of the method applied to quantitative analysis of LIBS is tested by experiments.
Abstract:To improve the dynamic cloud detection threshold value, moving and nesting analysis area methods were used to improve the dynamic cloud detection threshold method. Example analysis indicates that a lot of cumulus cloud always appears and there is little stratus in summer, and in this case the effective cloud detection threshold value obtained by basis fixed analysis area is 49%.The proportion of effective cloud detection threshold value is enhanced to 78.7% after adjusting basis analysis area to moving and nesting anaysis areas.In winter, stratus is a dominate cloud system, and it is easy to be distinguished from snow. The effective cloud detection threshold value is 43% by basis fixed analysis area in winter. The proportion of effective cloud detection threshold value is enhanced to 74.88% after adjusting basis analysis area to moving and nesting analysis areas .The analysis results show that the proportion of effective cloud detection threshold value is effectively enhanced by using moving and nesting anlysis area method and the accuracy of cloud detection is also improved.
Abstract:The general rule of deviations existed in the geolocation results of atmospheric infrared sounder (IRAS) image were investigated . The influence of scanning parameter deviation on geolocation was quantitatively analyzed by using scanning parameter correction model. A reference scheme was proposed to correct the geolocation deviation of AIRS images.It is shown that the corrected geolocation result is coincident with the World Geography Base Map and the feasibility of the scheme was verified.
Abstract:The idea of the combined block adjustment with variant satellite remote sensing images was proposed and the combined bundle block adjustment model was constructed. Some key issues were studied, such as construction of observation equation, computation of weight matrix, space intersection with multi-image and the frame of computation process. The validity of the model was confirmed by two experiments. The influences of the image combined form, and distribution, amount and precision of ground control points on the adjustment result were analyzed.At last, the characteristics and prospect of the combined block adjustment were summarized.
Abstract:Infrared small target detection is considered as a binary classification problem between target and background. According to the principal point spread function (PSF), infrared small target training set was simulated. Principal component analysis (PCA) was used to extract the main characteristics of target sample.Thus, the principal component space of thr target was established. Each test sample can be recognized as either target or background by its reconstruction error in the principal subspace. In order to improve the real-time performance, an infrared small target detection algorithm based on saliency and PCA was proposed . Salient regions probably containing targets were firstly detected by using spectral residual approach. Then target recognition was performed in the salient regions. Experimental results indicate that the proposed algorithm is fast and effective.
Abstract:Endmember extraction is the key procedure for spectral unmixing of hyperspectral remote sensing image. In the linear spectral mixture analysis, a convex invariance of simplex was introduced when hyperspectral remote sensing image was projected into null space of spectral signature matrix of endmembers. On the basis of the invariance, a null space spectral projection algorithm(NSSPA) was proposed. , One-unit endmember extraction strategies were established to implement the algorithm in a flexible way by designing different metrics and principles. It is proved that the proposed algorithm extends the algorithms based on subspace projection distance, including the classical orthogonal subspace projection(OSP) algorithm and the null space maximal distance algorithm. The algorithm provides diversified strategies for endmember extraction. In experiments results indicate that NSSPA demonstrates excellent performance of endmember extraction both in the simulated and real hyperspectral remote sensing images.
Abstract:In order to overcome the complexity of region merging in the segmentationimage of high resolution remote sensing image , an edge-guided segmentation method for multi-scale and high resolution remote sensing image was proposed. First，SUSAN operator was used to extract feature edges from the original test image. Then, an graph-based segmentation algorithm was used in the first-stage image segmentation and the following region merging stage, and extracted edges were efficiently used to guide merging process. To validate the proposed method, two experiments were performed on QuickBird image. The results were compared with segmentation results of eCognition and method without edge-guiding. The results show that this proposed method can efficiently depress the region merging in low-contrast areas for the traditional image segmentation algorithms, and make it possible to choose a reasonable segmentation scale in the whole image.
Abstract:Polarized features，which come from the surface of vegetation leaves in the process of reflectance, scattering and transmission of electromagnetic radiation, can be considered as the valuable information source in remote sensing information. The multi-angle earth observation can obtain more detailed and reliable 3-D spatial structure parameter of earth target, which makes the quantitative remote sensing possible. Multi-angle polarized hyperspectrum of the vegetation leaves becomes new way for quantitative remote sensing detection. In this study, an orthogonal and two level test containing three factors was designed on the basis of analyzing the characteristics of multi-angle polarized spectrum of vegetation leaves. Analysis of data variance shows that polarized angle, incidence viewing azimuth, the chlorophyll and their interactions effects all have impacts on the polarized reflectance of leaves. The influences of polarized angle, incidence viewing azimuth and their interaction are particularly significant. Hence, not only some single factors but also their interaction effects should be considered in the future studies of vegetation leaves polarized reflectance.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335