Li Yingle

The scale-transformation of electromagnetic theory and its applications

The scale-transformation of electromagnetic theory is investigated in detail based on the form of Maxwell equations in scale-transformation being unchanged in different coordinate systems. The relations of electromagnetic parameters in a rectangular coordinate system and in a spherical coordinate system are presented respectively. The scale-transformation invariants for electromagnetic field are derived and their physical meaning is also presented. It is indicated by simulation that the electromagnetic waves located in medium can be considered to be isotropic due to the fact that the size of propagating vector affected by the scale factors and observing azimuth is on a size of 10−9, which provides a new approach for investigating the electromagnetic characteristics of ellipsoidal targets.

The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction

The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction are derived. These fields in a particular case retrogress to those available in the literature. The obtained results have great potential in practical applications.

Anisotropic scattering for a magnetized cold plasma sphere

The transformation of parameter tensors for anisotropic medium in different coordinate systems is derived. The electric field for a magnetized cold plasma sphere and the general expression of scattering field from anisotropic target are obtained. The functional relations of differential scattering cross section and the RCS for the magnetized plasma sphere are presented. Simulation results are in agree with that in the literatures, which shows the method used and results obtained are correct and the results provide a theoretical base for anisotropic target identification etc.

Microwave propagation in charged sand particles

Based on the forward scattering amplitude function for charged sand particle under the Rayleigh approximation, the calculation model of microwave attenuation due to charged sand particles is given in terms of equisized distribution and exponential distribution. The attenuation is calculated and analyzed. The results show that the attenuation with charged sand is larger than without regard to charges on the sand surface, and the more concentrative the surface charges on sand particles are, the greater are the influence on microwave attenuation. The attenuation due to the sand particles following exponential distribution is greater than that due to the sand particles for the equisized distribution.

Electric fields inside and outside an anisotropic dielectric sphere

Analytical expressions of electric fields inside and outside an anisotropic dielectric sphere are presented by transforming an anisotropic medium into an isotropic one based on the multi-scale transformation of electromagnetic theory. The theoretical expressions are consistent with those in the literature. The inside electric field, the outside electric field and the angle between their directions are derived in detail. Numerical simulations show that the direction of the outside field influences the magnitude of the inside field, while the dielectric constant tensor greatly affects its direction.

Rayleigh Scattering for An Electromagnetic Anisotropic Medium Sphere

Based on the scales theory of electromagnetic waves, the analytical expression of electrical fields inside an anisotropic medium sphere is studied. Differential scattering cross section and radar cross section (RCS) for an anisotropic spherical target are presented. The correctness of the obtained results is tested. The simulation results show that the scattering of an anisotropic sphere has the property of a dipole radiation under the condition of Rayleigh scattering. The larger the dielectric constant is, the stronger the dipole scattering is. Anisotropy in magnetism only has an effect on differential RCS. These results provide a theoretical base for the identification of anisotropic targets.

Scattering of particles in wave beam based on series expansion

Based on the orthogonalities of the vector wave functions, the expressions of scattering fields are developed as the particle in the zero order field and in the first order fields of x, y, and z, respectively. A general relation between the expansion coefficients of scattering field and incident field is presented. Taking the elliptical beam for example, the scattering property of a particle in beam is investigated. After analyzing the effects of the beam waist, irradiating distance, etc. on scattering property, the validity of the proposed algorithm is demonstrated. Results show that the beam waist may improve the particle identification property and the particle has a strong scattering both in the forward direction and in the backward direction. The method proposed is simple and is a new way of researching the scattering from particles in electromagnetic beams.

Doppler shift of a laser pulse beam scattered by a rotating cone and cylinder

Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense.

General expressions of propagation vector of electromagnetic wave for lossless anisotropic media

Three general representations of the eign-propagating vectors are presented for the lossless anisotropic medium, respectively. When the lossless medium is uniaxial crystal, the phase velocities and the corresponding eign-propagating vectors are entirely agreement with what in the literatures, when the medium is an isotropic one, the phase velocities and the corresponding eign-propagating vectors are also agreement with what in the literatures in theory. The validity of the results is demonstrated. The representations of these eign-propagating vectors are not confined by the permittivity tensor.

Scattering of electromagnetic pulse wave by spherical sand and dust particles

The generalized Lorentz-Mie formulas are used to study the scattering characteristics when a femtosecond pulse illuminates a spherical sand and dust particle. Efficiencies for extinction and scattering of pulse wave by sand and dust particles are calculated for different radii and pulse duration. The calculations show that even for pulses with a constant carrier wavelength and pulse-filling coefficient, the efficiencies for extinction and scattering differ very much between the carrier wave and the different pulses.