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Jiao Z.,Tsinghua University | Yang J.,Tsinghua University | Yeh C.,Tsinghua University | Yeh C.,Beijing Institute of Radio Measurement and Metrology | Song J.,China Institute of Technology
IEEE Geoscience and Remote Sensing Letters | Year: 2014

In this letter, a modified three-component model-based decomposition method is proposed to solve the problem of instability present in the Freeman decomposition method. We incorporate the similarity parameter and introduce a new constraint that describes the relationship between the powers of scattering components. The proposed method minimizes a continuous objective function under a set of constraints, which results in the stability of the decomposition method. Furthermore, a fast algorithm for solving the optimization problem is developed to accelerate computation. We demonstrate the stability of the proposed decomposition method by using the E-SAR polarimetric data acquired over the Oberpfaffenhofen area. © 2013 IEEE.

Chen W.,Beihang University | Xu X.,Beihang University | Wen S.,Beijing Institute of Radio Measurement and Metrology | Cao Z.,Beijing Institute of Radio Measurement and Metrology
IET Radar, Sonar and Navigation | Year: 2011

In this study, a novel two-stage virtual array element construction procedure is proposed for super-resolution direction finding of multiple narrowband coherent point sources with a sparse array consisting of two or more far-separated subarrays. An all-pole model is used to fit to the array snapshot and the corresponding model parameter estimation methods are discussed. Virtual elements between and outside the subarrays are then constructed in sequence using different approaches, namely, the semi-parametric and non-parametric techniques, to increase the effective array aperture size. As a result, a great improvement in angular resolution is achieved. Compared with the existent procedure using minimum weighted norm (MWN) only, the proposed procedure is superior in sidelobe artefact reduction and weaker adjacent source detection as a result of its inherent low sidelobe level. Numerical simulations also demonstrate that under lower signal-to-noise ratio or with fewer snapshots, the proposed procedure has better performance than the one using MWN only in both resolution and accuracy, as well as the conventional estimation of signal parameters via rotational invariance techniques in accuracy, although such advantages tend eventually to disappear with reduced target angular spacing. © 2011 The Institution of Engineering and Technology.

Wang J.,Beijing Jiaotong University | Yang Y.,Beijing Institute of Radio Measurement and Metrology | Miao J.,Beihang University | Chen Y.,National Key Laboratory of Metrology and Calibration Technology
IEEE Transactions on Antennas and Propagation | Year: 2010

Internal calibration source provides reference data for remote sensing system. Realistic calibration source is constructed by finite periodic structure, and hence, the emissivity calculation is different from the infinite periodic array case. In this paper, conventional indirect method based on the scattering field is modified first, so that it can be used to calculate the emissivities of finite homogeneous objects. Subsequently, a new method based on antenna concept is proposed for calculating the differential scattering coefficients and emissivities of the inhomogeneous finite objects. The methods are then applied to finite circular pyramid arrays covered with an absorbing material, and the results are analyzed. Furthermore, the effect of the illuminating scope of incident wave on the emissivity and differential scattering coefficient of circular finite pyramid array is studied. © 2006 IEEE.

Guo Z.-H.,Shandong University | Li D.,Wuhan University of Technology | Zhang B.-Y.,Beijing Institute of Radio Measurement and Metrology
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2013

Radar target recognition is increasingly important with the development of radar techniques and the urgent military requirements. The research on radar target recognition using one-dimensional high range resolution profiles is a popular area in the radar and signal processing community. The range profiles can not only provide the information on shape and structure of the target but also be obtained easily. So far extensive research work has already been made in the field of non-cooperative target recognition using the range profiles. The feature extraction algorithm, classification algorithm and joint tracking and recognition algorithm based on the radar range profiles are summarized. Finally, the still open problems are discussed and some suggestions on the solutions and research trends are proposed.

Yao L.,Beijing Institute of Radio Measurement and Metrology | Ma W.,Beijing Institute of Radio Measurement and Metrology
IEEE Transactions on Electromagnetic Compatibility | Year: 2015

A previous paper mentioned that the international standard ISO 11452-4:2005 has given a requirement for the calibration fixture of current probe, i.e., the voltage standing wave ratio (VSWR) of the calibration fixture should be less than 1.2. Here is a comment about this. © 1964-2012 IEEE.

Lu D.,CAS Institute of Semiconductors | Pan B.,CAS Institute of Semiconductors | Chen H.,Beijing Institute of Radio Measurement and Metrology | Zhao L.,CAS Institute of Semiconductors
Optics Letters | Year: 2015

A widely tunable optoelectronic oscillator (OEO) based on a self-injection-locked monolithic dual-mode amplified feedback laser (DM-AFL) is proposed and experimentally demonstrated. In the proposed OEO structure, the DMAFL functions as an active tunable microwave photonic filter (MPF). By tuning the injection current applied on the amplifier section of the AFL, tunable microwave outputs ranging from 32 to 41 GHz and single sideband phase noises below .97 dBc/Hz at 10 kHz offset from the carriers were realized. © 2015 Optical Society of America.

Wang J.,Nanjing University of Science and Technology | Shen Z.,Nanyang Technological University | Wu W.,Nanjing University of Science and Technology | Feng K.,Beijing Institute of Radio Measurement and Metrology
Optics Express | Year: 2015

A wideband linear-to-circular polarizer is proposed, which consists of an array of dielectric slabs with double-sided parallel metallic strips. The polarization conversion is achieved by decomposing the linearly polarized incident plane wave into two orthogonal components of equal amplitude, which are subjected to an unequal phase shift such that the resultant phase difference between two components is 90° after an appropriate propagation path. The metallic strips are introduced to enhance the axial ratio bandwidth. Microwave experiment is performed to successfully realize these ideas and measured results are in good agreement with numerical simulations. The frequency range over which the measured transmission coefficient is higher than 0.95 is from 7 to 13.7 GHz, and the 3 dB axial ratio bandwidth under normal incidence ranges from 7 to 13 GHz, corresponding to a 60% fractional bandwidth. In addition, the proposed polarizer shows a good stability with respect to the oblique incidence. © 2015 Optical Society of America.

Che Z.-P.,Beijing Institute of Radio Measurement and Metrology
Hedianzixue Yu Tance Jishu/Nuclear Electronics and Detection Technology | Year: 2011

There are many methods about time interval measurement such as count method, vernier method, analog inter-plug, delay line inter-plug and time-to-voltage method. After having analyzed and compared these methods, It provided a new method with high precision and large range, and showed the principle and technique of the design. The method had successfully applied to GPS rubidium clock, and it will provide a good reference scheme for other designs.

Gao H.,Beijing Institute of Radio Measurement and Metrology
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

Next Generation Radar (NGR) concept achieves high sensitivity, better accuracy, and good transportability, while the distributed aperture coherence-synthesizing radar is an important direction, which coherently combining multiple close distributed radar apertures. Some basic study on this new-type radar is performed with several experiment results. © 2011 IEEE.

Wang W.,Beijing Institute of Radio Measurement and Metrology
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2014

Vacuum thermal insulation of the thermostat control unit of hydrogen atomic clockwas physically modeled, numerically simulated with software package Ansys, and experimentally evaluated to reduce the negative impact of environmental temperature on its accuracy. The influence of the thermal insulation conditions, such as the pressure in the vacuum layer, vacuum wall materials, and environment temperature, on the temperature sensitivity was evaluated. The prototyped vacuum thermal insulator was designed, constructed, and tested. The test results show that the newly-developed vacuum thermal insulationsignificantly reduced the temperature sensitivity of the hydrogen atomic clock from 1×10-14/°C to 2.5×10-15/°C, close to the best result reported (1×10-15/°C).

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