利用表面电磁波进行能量分配的研究

研究了二维分界面上的表面电磁波,推导得出二维分界面上TE表面电磁波的电场强度、磁场强度和能流密度的表达式,得到分界面上表面波的存在条件,根据总能流把分界面分为左手分界面和右手分界面,对二维分界面上表面电磁波的传播进行仿真,最后提出利用表面电磁波进行能量分配,并给出了仿真结果.     

Nondestructive Measurement of a Dielectric Layer Using Surface Electromagnetic Waves

In this investigation, the possibility of nondestructively measuring the thickness and dielectric constant of a layer of dielectric material on a conducting substrate by surface electromagnetic waves (SEW) has been demonstrated. The theoretical approximate dispersion relations near cutoff were derived for both the TE and TM modes and found to be linear functions of frequency, the thickness and dielectric constant were then calculated as simple algebraic functions of the slope and intercept of the dispersion curve. An experimental apparatus utilizing a prism-coupler was constructed to excite surface electromagnetic waves in a dielectric layer whose characteristics were known. By suitable measurements of the frequency and the coupling angle of the source, the dispersion curve was determined experimentally and the resulting dielectric constant and thickness of the layer calculated.     

声表面波混频谐波的实验观察

基于超声无损检测技术的需要,该文在理论分析声表面波混频效应的基础上,提出了一种混频声表面波的激发方法,并进行了相应的声表面波混频谐波的实验观察研究。设计并制作了以斜入射的体横波和体纵波分别激发声表面波的楔块,通过选择适当的体横、纵波激励信号的周波数及时间延迟,可使斜入射体横、纵波分别激发的声表面波完全混叠。通过对接收到的混叠声表面波时域信号进行脉冲反相处理和傅里叶变换,得到明显的声表面波混频谐波信号。结果表明,借助于楔块两列斜入射的体横、纵波可有效产生混频声表面波,实验观察与理论预期一致,这为发展基于混频声表面波的超声无损检测技术奠定了基础。     

On Polarization Selection of Electromagnetic Waves and Its Realizability

The realizability of polarization selection of electromagnetic waves is proved. The possibility of determination of the polarization of the radiated wave even in the case an arbitrary variation in the mutual positions of transmitting and receiving antennas is shown.     

On the Theory of Shielded Surface Waves

An analysis is given for the modes which will be excited between two parallel impedance boundaries. It is shown that, for inductive-type surfaces, two of these modes have a surface wave character even though the structure is bounded in the transverse dimension. The interaction between these surface waves and the accompanying waveguide modes is discussed for this model which is admittedly highly idealized.     

电磁超声表面波产生机理的ANSYS仿真

针对电磁超声在金属表面缺陷检测的应用问题,研究了电磁超声表面波的产生和传播机理,根据电磁超声产生原理,采用有限元仿真分析软件ANSYS,对电磁超声表面波的产生过程进行了偏置磁场、工件表面感生涡流和所受洛伦兹力、振动产生超声波三部分的仿真.仿真结果表明通有交变的线圈在工件感生出交变的涡流,在偏置磁场的作用下,工件表面质点受到与激励电流和感生涡流频率相同的洛伦兹力,在这个力的作用下,质点发生位移,并以表面波的形式向外传播.     

On the Possibility of the Propagation of Solitary Electromagnetic Waves in Bigraphene

The possibility of the propagation of a solitary electromagnetic wave in bigraphene, between the layers of which a potential difference is applied, is studied. The condition is found under which the formation of such a wave is possible. The dependence of the solitary-wave shape on the potential difference between graphene layers is studied. As possible solitary-wave identification, the electric charge carried away by the wave in the direction of its propagation is calculated.     

Velocity Modulation of Electromagnetic Waves

This paper deals with electromagnetic wave propagation through dielectric media whose propagation constants vary as a function of time. If the parameters of the medium cannot respond to changes in the electric and magnetic fields of the propagating wave, the fields within such media will be linear. Maxwell's equations are solved for cases in which the scalar permittivity and permeability vary independently with time. When the impedance is constant, an exact solution is obtained. When the impedance varies, a closed form approximation is found since an exact solution is not always possible. The field energy and electromagnetic momentum are derived for a velocity transient and it is seen that, in general, the energy changes and the momentum remains constant. The frequency deviation that results when a monochromatic wave is passed through a section of dielectric with nonconstant velocity of propagation is discussed in detail. An approximate solution is obtained for the case in which the electrical length of such a section is small; it is found that essentially linear phase modulation occurs. The general solution is found for the case in wtilch the electrical length of section is long and the permittivity of the medium sinusoidally modulated. The optimum length found to give the greatest frequency deviation is shown to be generally impracticable. It appears that ferroelectric or ferrimagnetic velocity-modulated dielectrics are feasible, at least for low-power modulators.     

平板与正弦型组合粗糙面的电磁波复合散射

分别用正弦型组合粗糙面和正弦型二维粗糙面模拟海洋表面，建立了海上目标电磁散射的简化模型，用物理光的双次反弹来表示目标与组合粗糙面之间的电磁波相互作用。     

电磁波在等离子体中的传播衰减

针对通信黑障的问题,文中从电磁波在等离子体中的传播特性出发,利用Matlab数值仿真,研究不同电磁波频段,不同等离子体参数,包括等离子频率、碰撞频率、等离子温度、压强等对电磁波传播衰减的影响,以及外加磁场作用下,不同极化的电磁波在等离子体层的传播衰减特性。研究结果表明:外加磁场可明显降低圆极化电磁波衰减,并且当外加磁场满足一定条件,大于最小磁场强度时,电磁波衰减小于10 dB;且同等条件下右旋极化比左旋极化电磁波的衰减更小,为了获得较小的电磁波衰减,右旋极化电磁波所需的磁场强度也小于左旋极化。     

时变等离子体与电磁波相互作用研究

通过实验验证了时变等离子体对电磁波产生的调制,证明了该调制的频率与等离子体变化频率保持一致,该调制本质是因为电磁波进入等离子体后波矢发生了改变,导致电磁波的幅度和相位产生了变化等离子体类似色散介质。随着信号的频率上升,等离子体调制的强度减弱。对调制后的信号进行解调幅和解调相,验证了调幅信号和调相信号具有同周期,但是周期内的变化不一样。     

Toroidal Resonators for Electromagnetic Waves

The solution of Maxwell's equations for toroidal systems has been reduced to the solution of the scalar Helmholtz equation. The eigenfunctions and the corresponding electromagnetic fields have been calculated analytically. The dispersion relation was formulated. Three different types of eigenmodes were obtained for each frequency. The structure of the electromagnetic field of the m= 0,1,2, and 3 modes is analyzed.     

脉冲电磁波波形的变化规律＊

本文研究脉冲电流激励的电磁波波形及其随轴向距离的变化规律。     

Electromagnetic Waves in Waveguides with Wall Impedance

A variational expression for the propagation constant of the waves in waveguides with inhomogeneous media and with wall impedance is presented. Using this expression, the shift of the propagation constant due to the wall impedance is calculated. It is also clarified how the removal of degeneracy takes place. Then the same problem is discussed using another approach, a perturbation method. The result is identical with that of the variational principle, as is to be expected. In the final section, taking degenerate TEM modes as an example, it is shown that appropriate choices of field configuration are necessary when the formula for an attenuation constant derived from the conservation of energy is applied to degenerate modes.     

Range-Doppler Resolution of Electromagnetic Walsh Waves in Radar

A number of papers have appeared during recent years about electromagnetic waves produced by antenna currents with the time variation of Walsh functions rather than that of sinusodial functions. Experimental transmitters and receivers for such waves have been developed. There are a variety of effects of Walsh waves that do not exist for sinusoidal waves or are so obscure that they are generally not recognized. This makes a discussion of these effects difficult for the nonspecialist. The range-Doppler resolution in radar lends itself more readily to a discussion, since Walsh waves bring in this case not a new effect, but only a substantial improvement of a well-known one. It is shown that our present technology should permit an improvement of about one order of magnitude in the Doppler resolution by using carriers derived from Walsh or other two-valued functions rather than sinusoidal functions. The theoretical improvement of the relative range resolution is substantially greater since it no longer depends upon the duration of the modulating signal but upon the period of the carrier and the switching time of the carrier. The absolute range measurement is not changed.     

On the Effect of Absorbing Materials on Electromagnetic Waves with Large Relative Bandwidth

Coats of absorbing material over metallic surfaces can substantially reduce the energy of a returned radar signal. This paper analyzes the effect of such coatings on radar signals with large relative bandwidths close to 1, rather than the conventional relative band- widths in the order of 0.01 or less. Normal incidence of the wave, and absorption due to ohmic losses are assumed. The purpose of the paper is strictly to draw attention to the significance of a change from small to large relative bandwidths, since the decades of work on the reflection of sinusoidal waves with various angles of incidence by targets with various shapes, constructed with a variety of materials, cannot be duplicated for nonsinusoidal waves with less than corresponding decades of effort.     

雨滴对船用雷达电波的作用

本文讨论雨滴对船用雷达的两个波段，即Ｓ波段和Ｘ波段雷达电波的辐射和吸收作用，并且对辐射和吸收作用作出比较，对Ｓ波段和Ｘ波段的作用也作出了比较。     

Interaction of Electromagnetic Waves with Cylindrical Plasma

Exact numerical solutions are given for the interaction of a plane, electromagnetic wave with a cylindrical plasma. The incident wave is normal to the plasma axis and both TE and TM polarizations are considered. The electron density profile is represented by a Gaussian curve consistent with flow-field calculations for wakes and jets. Transmitted and scattered amplitudes are evaluated as functions of the polar angle and plasma parameters. The data are compared with previous theoretical and experimental work. [17],[18] Parabolic electron density profiles are also investigated and contrasted with the Gaussian results. The sharp cutoff in a parabolic profile has a significant effect on the electromagnetic interaction. Applications to microwave diagnostics are discussed including a new bistatic method.