Time filter

Source Type

Shen H.,Ocean University of China | Wu S.,Ocean University of China | Qin S.,Beijing Huahang Radio Measurement Institute | Liu J.,Ocean University of China | And 2 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2014

Frequency stability of Q-switched Nd:YAG laser significantly affects the wind measurement accuracy of direct detection Doppler Lidar. The typical free frequency drift of diode-pumped Nd:YAG laser working at doubling frequency 532 nm based on seed injection can reach 15 MHz/min, correspondingly to a weed speed measurement error of 4 m/s. By using virtual instrument control technology of Labview, the frequency of pulsed laser is successfully scanned, and iodine absorption line 1109 is matched automatically, which get the frequency on one of the two slopes of the line. Standard deviation of frequency stability is about 0.8 MHz for a long time (more than 2 h), while the equivalent wind speed error is 0.2 m/s. The requirement of frequency stability is achieved during long-term lidar measurements.

Lan S.-C.,Harbin Institute of Technology | Zhang X.,Beijing Huahang Radio Measurement Institute | Pan R.,Harbin Institute of Technology | Li J.-H.,Harbin Institute of Technology
Proceedings of the 2011 6th IEEE Conference on Industrial Electronics and Applications, ICIEA 2011 | Year: 2011

Considering the on-board clock stability, the paper presents a method of timing calibration strategy based on the observation of pulsars, a natural celestial source, in order to improve the timing accuracy. A calibration model is established and the error factors are considered based on the characteristic of pulsars' stable and periodical signals, and the pulsar timing residuals are caused by reference normal clock and pulsar itself, and the two influences are not correlative. Firstly, filters such as wavelet and HHT are implementing to data handling and error analysis, and then the paper investigated and developed a multiple-pulsar-observation method. Judging from the signals transmitted from different pulsars, the onboard timing residuals are determined by credibility weight of different pulsars' observation different components. Finally this paper comes to the conclusion via simulations. The method allows separating the error from a single pulsar timing errors and the on-board time can be obtained by filtering the observation residuals of pulsars observed, extracting the filtering result of different pulsars, and then choosing the weight according to the stability of timing result denoted with timing variance. © 2011 IEEE.

Wu X.,Beihang University | Wu S.,Beihang University | Xing Z.,Beihang University | Zhang W.,Beijing Huahang Radio Measurement Institute
Proceedings of the 2015 27th Chinese Control and Decision Conference, CCDC 2015 | Year: 2015

The problem of seeker allocation and target assignment (SATA) of multiple hetero-seeker missile formation in the anti-ship cooperative attack was investigated in this paper. A calculation model of penetration probability and a model of SATA for the missile formation attack were designed, considering the characteristics of the missile seeker, the operational process of the missile formation cooperative attack, the shipboard anti-missile weapons with the constraints of the ammunition restrictions and the target value. Then a method based on genetic algorithms (GA) was presented, with novel encoding, modified initialization, crossover and mutation operations. Simulations demonstrate the viability of the proposed method, showing that the missile formation penetration probability increases by 10% using the proposed algorithm; it could provide basis and reference for actual combat operation. © 2015 IEEE.

Jia X.,Harbin Institute of Technology | Zhao C.,Beijing Huahang Radio Measurement Institute
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2011

In modern tactical missiles terminal guidance system, strap-down stable scheme is prior to traditional gyro stable scheme in cost and volume, and is a new direction of missile seekers. The critical technique of strap-down terminal guidance system is the so called mathematical stabilization platform and strap-down stable control algorithm. The stabilization control scheme and guidance information extract approach of terminal guidance system with a semi-strap-down structure were discussed. A practical mathematical stabilization control algorithm and the relevant line of sight (LOS) angle rate extract method were devised, which was suitable for engineering implementation. First of all, the principle of strap-down stabilization control was discussed. After that, a new control law of the mathematical platform was described, together with a calculation algorithm of guidance information such as LOS angle and LOS angle rate. Moreover, in order to overcome the deficiency of calculation precision caused by imprecision of sensor's measurement and non-ideality of differential operation, a practical evaluation filter model of LOS angle rate was given out based on the angle tracking model of a missile to a target. Finally, computer simulations were made which verified the efficiency of above methods.

Wang W.,Harbin Engineering University | Liang D.,Harbin Engineering University | Wang Z.,Beijing Huahang Radio Measurement Institute | Yu H.,Harbin Engineering University | Liu Q.,Harbin Engineering University
Radioengineering | Year: 2015

The work presented in this paper is aimed at the implementation of a real-time multiple-input multiple-output (MIMO) imaging radar used for area surveillance. In this radar, the equivalent virtual array method and time-division technique are applied to make 16 virtual elements synthesized from the MIMO antenna array. The chirp signal generater is based on a combination of direct digital synthesizer (DDS) and phase locked loop (PLL). A signal conditioning circuit is used to deal with the coupling effect within the array. The signal processing platform is based on an efficient field programmable gates array (FPGA) and digital signal processor (DSP) pipeline where a robust beamforming imaging algorithm is running on. The radar system was evaluated through a real field experiment. Imaging capability and real-time performance shown in the results demonstrate the practical feasibility of the implementation.

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