One-Dimensional Range Profile Of Terahertz Pulse Of The Beam On Ball And Ellipsoidal Target

Scattering properties of terahertz imaging technology and research in national defense and military as well as civilian areas have significant scientific value and broad application prospects. According to Kirchhoff approximation, based on the basic theory of scattering field, beam scattering theory and the basic pulse scattering theory, the high-frequency approximation and far-field approximation, study and discuss the rough target of coherent and incoherent scattering properties of terahertz waves plane, thereby obtain the scattering characteristics in time-domain and frequency domain of terahertz beam incident rough target, discuss some problems about terahertz imaging simulation of one-dimensional distance, mainly as follows:1. Based on the radar cross-section and the definition of RCS, same as the definition of infrared and microwave, deduce THz scattering cross-section formula expression, and analyze the impact of the target surface roughness statistical parameters and metal dielectric parameters on scattering cross section of the main factor.Described in the methods of getting the material optical constants from terahertz measurements. Under reflective type and the transmission type of terahertz time-domain spectroscopy system,and type without substrate, the material of the optical parameter extraction methods is introduced. Through the terahertz time-domain spectroscopy system error analysis, how to choose material and preparation is discussed.2. Compared analysis of methods and means in microwave and laser research radar cross section, with the conclusion that the scattering cross section of an arbitrary object can be divided into coherent and incoherent scattering depart,select Kirchhoff method to research terahertz radar cross section. By the rough surface scattering method Kirchhoff scalar approximation theory, we deduce a rough target coherent scattering cross section of expression in terahertz.It can be presented as the corresponding target smooth conductor cross-section, the characteristic function and the target surface mirror point the product of the Fresnel reflection coefficients of three parts. When calculate the Incoherent scatter section, the target can be separated into a series of small bins, incoherent scattering cross sections can be obtained by adding every bin of RCS in terahertz. Numerical study and examine the influence of the metal dielectric parameters, surface roughness statistical parameters and polarization characteristics of a rough sphere, ellipsoid in coherent and incoherent scattering characteristics.3. Enter the basic nature of the Gaussian beam field. Through the use of flat spectral expansion method and the physical optics approximation, Gaussian beam field can be seen by the propagating in different directions, different amplitude superposition of plane waves. Based on rough surface scattering theory, obtain the coherent and incoherent scattering cross section in terahertz Gaussian beam expressions. Coherent terahertz beam scattering cross-section equivalent the impact of beam factor with the results of plane wave scattering. Terahertz Beam with the incoherent scattering cross section also relates beam parameters. Numerical discuss the cross section of a rough sphere and ellipsoid in terahertz beam, analyze the impact of beam width, surface statistical parameters and the metal surface of the dielectric parameters.4. According to the basic theory of time-domain pulse scattering, the coherent component of two frequency mutual coherent functions is the key to solve the problem on terahertz pulse scattering problem. Combined with beam scattering theory in the frequency domain, obtain the expressions of coherent and incoherent component function, then obtain the scattering beam impulse response. Depending on the above theory, the scattering power of the incident pulse is the convolution of the power of the incident pulse and the backward to the impulse response. Calculate the one-dimensional image of a rough sphere, ellipsoid in terahertz pulse, analyzes the target size, waist width, pulse width, and the geometry of the target factors.