Parameter Estimation of Target with Micro-Motion Based on Terahertz Radar
General model is established for the echo signal of a target with micro-motion. Then time-frequency analysis and Hough transform are utilized for motion parameter estimation and radar signature extraction in terahertz band, and the estimation of reflectio
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Parameter Estimation of Target with Micro-Motion Based on Terahertz Radar Jian Tu, Zhengwu Xu, and Jin Li
Abstract General model is established for the echo signal of a target with micro-motion. Then time-frequency analysis and Hough transform are utilized for motion parameter estimation and radar signature extraction in terahertz band, and the estimation of reflection coefficients of scatterers is completed through NLS and CLEAN algorithm. The simulation result shows that this method of Hough transform has the advantages of high precision and strong anti-noise. The model of echo signal and method of parameter estimation are useful for radar target detection and identification. Keywords Micro-Doppler • Time-frequency analysis • Feature extraction • Hough transform • Parameter estimation
52.1
Introduction
Mechanical vibration or rotation of structures in a target may induce frequency modulation on returned signals and generate sidebands about the center frequency of the target’s Doppler frequency [1]. The modulation due to vibrations and rotations is called micro-Doppler phenomenon. Micro-Doppler phenomenon is very common in nature, such as the human heartbeat, vibration or spin of missile warheads, etc.. . . while in terahertz band micro-Doppler phenomenon is particularly significant. In this chapter, considering the micro-motion of target in the terahertz band, the echo model is established [2], time-frequency transformation and Hough transform are applied to extract the micro characteristic parameters [3–6], and the estimation
J. Tu (*) • Z. Xu • J. Li School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, China e-mail: [email protected] Q. Liang et al. (eds.), Communications, Signal Processing, and Systems, Lecture Notes in Electrical Engineering 202, DOI 10.1007/978-1-4614-5803-6_52, # Springer Science+Business Media New York 2012
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of reflection coefficient of scatterers is completed through nonlinear least squares and the CLEAN algorithm [2, 7]. These are very helpful for radar target detection and identification [8].
52.2
Target Echo Modeling
We assume a target of multiple scatterers containing macro- and micro-motion to do a compound movement on the radar radial direction. Its movement rule is a higher order polynomial of time t or the infinite series oft. Weierstras quantitative shows that arbitrary radial rule of motion may be a finite polynomial of t approximation R1 ðtÞ
n X
aj tj
(52.1)
j¼0
where n is the number of finite polynomial, micro objectives of the target can be approximated as vibration or rotation movement, its rule of motion is R2 ðtÞ ¼ A sinðBt þ ’Þ
(52.2)
where A is the vibration amplitude, B is the frequency of vibration, ’is the initial rotation angle. Then the echo of target can be expressed as SðtÞ ¼
k X i¼1
"
!# n X j4pf 0 R0 þ si exp aj tj þAi sinðBi t þ ’i Þ c j¼0
(52.3)
where si is the scattering coefficient of the ith scatterer, R0 is the initial distance between radar and target,f 0 is
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