The spectrum of radar signal will be modulated by moving target or vibration and turning part of the target,
this is called micro-Doppler effect. It is a new way of using micro-Doppler effect to realize the feature extraction and
target recognition. Because the complex vibration target has more complicated frequency component than the single
frequency target, so it is very useful to do the research of simulation and experiment of laser micro-Doppler effect for
detecting complex vibration. In this paper, the research on simulation and experiment of laser micro-Doppler effect for
detecting complex vibration of moving target was developed based on the simulation research of micro-Doppler effect in
lidar. Firstly, the geometry of complex vibrating target detection in radar was established. Secondly, the simulation and
experiment signal sources were compared and also the returned signals in radar of the simulation and experiment were
compared, the compared results showed that the two complex signal sources were very similar, and the frequency
change trend of returned signals in radar was the same. Thirdly, joint time-frequency analysis method of the reassigned
smoothed pseudo Wigner-Ville distribution (RSPWVD) was introduced to analyze the signals. The results showed that
in RSPWVD, the waveform of the vibration target, the target vibration period, the Doppler frequency shift and the
target’s speed can be got. The simulation results and the experiment results got by the RSPWVD had the basically same
frequency characteristics. So the RSPWVD can reflect very well the micro-Doppler characteristics of moving target’s
complex vibration. In conclusion it proved the validity of the simulated model, also it proved that using this
time-frequency method to analyze the micro-Doppler signal of complex vibration was correct. And it laid the foundation
of further using lidar to realize the classification and identification of target.
KEYWORDS: Acoustics, Signal detection, Wavelets, Data acquisition, Signal generators, Fourier transforms, Wavelet transforms, Signal to noise ratio, Signal processing, Electronic filtering
With the localizing character of wavelet transform, acoustic signal from water surface using laser light can be decomposed into the detail part of every scale by multi-resolution analysis. The results of experiment show that wavelet analysis has the great ability of noise rejection and is fit for weak signal detection and feature extraction.
Fourier-transform infrared spectroscopy is an efficient technique for the detection and quantification of molecules in gas mixtures. A passive infrared system was used to detect specific hazardous clouds in the atmosphere and sound an alarm in time. The Fourier transform infrared spectrometer is operated in the 8-12 atmosphere window region of the spectrum. A spectral identified system of hazardous clouds is based on neural network. The network is trained by the use of the backward-error-propagation algorithm. The identical results of the target spectra from the open-air have demonstrated that the detection-integrated system may be used to detect and identify the infrared spectra of hazardous clouds.
Infrared spectra from the several typical pollution clouds are observed remotely using a passive Fourier Transform Infrared Spectrometer. The primary purpose of the study is to determine an efficient method to distinguish hazardous-cloud from several clouds. Spectral pattern recognition techniques are employed to suppress the strong and highly varying background to extract the very weak emission features from measured spectra. It can be used to discriminate specific pollution cloud between several smokes and interferents.
The development of effective methods in environmental pollution control is a main task of environmental research. Fourier-transform IR spectroscopy is an efficient technique for the detection and quantification of molecules in gas mixtures. A passive IR system designed to detect specific pollution clouds in the atmosphere and sound an alarm in time. The sensor is a Fourier transform spectrometer operating in the 8-12 micrometers atmosphere window region of the spectrum. The system can be operated unattended and be highly reliable and accurate in its decisions. An on-board microcomputer will be applied to achieve automatically control of system, acquire data, process it and make decisions. The paper describes the signal processing and spectral pattern recognition techniques. Measurement results for ambient air with the spectrometer are reported.
Computed Tomography (CT) is a modern medical diagnostic technique in which x-ray transmission measurements at numerous angles through the human body are processed by computer to produce cross-sectional pictures of the body. This technique also has found applications in such diverse fields as materials testing, astronomy, microscopy, image processing and oceanography.In this paper, a modification of this technique, using emitted IR or microwave radiation instead of transmitted x-ray radiation, can be applied to satellite radiance measurements taken along the orbital track at various angles. The channels of IR sensors for the CT retrieval are selected from HITRAN Database, and analyzed by Eigen-value analysis. We discuss in detail the effect retrieval result of CT technique form projection-angle. Finally, using the balloon sounding data, the result of CT are compared with the result of conventional method. Because the advantage over conventional remote sensing methods is the additional information acquired by viewing a given point in the atmosphere at several angles as well as several frequencies. The results show that the temperature profiles by CT retrieval are better than the conventional method.
A real-time compound identification system for Fourier Transform Infrared Spectroscopy data has been based on the direct comparison of interferograms. Statistical pattern- recognition methods are applied to the feature extraction of infrared interferograms. Using large training sets, a real- time classification filter has been developed that is able to discriminate the specific-compound of infrared interferograms, and it has a very high probability. Our system can be used to identify several specific-compounds (several chemical vapors) of infrared interferograms of remote detection.
We have constructed wavefront compensated system that measures wavefront tilt of light propagation through the laboratory-generated turbulence in a convective tank. The measurements of optical characteristic in simulation cell have been measured. The wavefront tilt power spectral density and arrival-angle of fluctuations are also shown simultaneously The spectra show distinct asymptotic slopes, in general, agree with theoretical predictions based on the Kolmogorov model. The distribution variance of arrival-angle fluctuations follows (Chi) 2 distribution.
We have constructed wavefront compensated system that measures wavefront tilt of laser through the generated turbulence of the convective tank in laboratory. The wavefront tilt power spectral density has been measured. The measurements of optics characteristic in tank have been also measured simultaneously. The spectra show distinct asymptotic slopes, in general, agree with theoretical pre- dictions based on the Kolmogorov model. This paper reports on the results of some experiments made to evaluate the performance of the system, and to improve characteristics of turbulence in the con- vective tank. Spectral analyses of these signals allow to study bandwidth of this system. We study the behaviour of image distortion in order that the compensation system can be established.
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