Target recognition by vibrometry with a coherent laser radar

Laser vibration sensing can be used to classify military targets by its unique vibration signature. A coherent laser radar receives the target´s rapidly oscillating surface vibrations and by using proper demodulation and Doppler technique, stationary, radially moving and even accelerating targets can be taken care of.A frequency demodulation method developed at the former FOA, is for the first time validated against real data with turbulence, scattering, rain etc. The issue is to find a robust and reliable system for target recognition and its performance is therefore compared with some frequency distribution methods. The time frequency distributions have got a crucial drawback, they are affected by interference between the frequency and amplitude modulated multicomponent signals…


1 Introduction
1.1 Background
1.2 Objectives
2 Atmospheric laser propagation theory
2.1 Disturbances on reflected laser radar beam
2.1.1 Clutter
2.1.2 Turbulence
2.1.3 Speckle
2.1.4 Weather conditions
2.2 The reflected signal
2.2.1 Doppler shift
2.2.2 Modulation index
3 Time frequency signal analysis methods
3.1 Linear time frequency representation
3.2 Quadratic time frequency representation
3.2.1 Spectrogram
3.2.2 Wigner distribution
3.3 Statistical peak distribution
3.3.1 Detection of peaks
3.3.2 Distribution of peaks
3.3.3 Amplitude variations of peaks
3.4 The modified FOA method
3.4.1 Algorithm description
3.4.2 Acceleration estimation
3.4.3 Mixing by IQ-representation
3.5 Comparison of different methods
3.5.1 Software development
3.5.2 The modified FOA method
3.5.3 Statistical peak distribution
3.5.4 Spectrogram
3.5.5 Wigner distribution recognition by vibrometry
4.1 Specification of data
4.2 US Air Force laser system
4.3 Target properties
4.4 Different aspects for a certain vehicle
4.5 Tone comparisons
4.5.1 Vehicle A
4.5.2 Vehicle B
4.5.3 Vehicle C
4.5.4 Vehicle D
4.5.5 Vehicle E
5 Discussion and conclusions

Author: Olsson, Andreas

Source: Linköping University

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