Effects of Birefringence Within Ice Sheets on Obliquely Propagating Radio Waves

In this paper, effects of birefringence on radio waves obliquely propagating though polar ice sheets are examined to facilitate interpretations of bistatic and side-looking radar data. A formalism applicable for arbitrary radar configurations is developed to predict the returned power from within and beneath the ice sheets that have arbitrary alignments of ice crystals (ice fabrics). We applied this formalism to a range of ice fabrics found in ice cores and assessed the effects of birefringence in terms of ray-path configurations, ice fabrics, and radar frequency. Predicted frequency dependence of the bed return power replicates prominent features observed at Greenland NGRIP ice-core site. Results show that birefringence in ice of 1 km or more thickness with strong (weak) fabric can reduce the power returned from the bed 2 dB or more at frequencies higher than 200 MHz (20 MHz) as compared to isotropic ice. This suggests that quantitative interpretation of the power returned from the bed requires careful assessment of birefringence almost everywhere over the ice sheets. Application of this formalism also suggests a radar-frequency range usable for attenuation measurements, possible effects of fabric on synthetic aperture radar processing, and a feasibility of remote sensing of ice fabric.     

双各向异性手征Ω介质板中电磁波的传输特性

应用广义谱域指数矩阵方法，本文研究了单层和双层双向向异性手征Ω介质板在斜入射电磁波的照射下的反射和透射性。重点分析了由于Ω单元不同取向引起 反射和透射波中的交叉极化转换效应，和不同本构参数对反射、透射系数的影响。     

Plane Waves Propagating in Chiral Plasma and Chiral Ferrite Media

Plane wave propagation in chiral plasma and chiral ferrite media is studied in kDB coordinate system. General wave equations and characteristic equations of plane waves propagating along an arbitrary direction in chiral plasma and in chiral ferrites are derived in simple formulations respectively. Four wavenumbers and their corresponding dispersion characteristics are resulted for propagation both along and normal to the biasing magnetic field. When plane wave with negative helicity propagates along the biasing magnetic field in chiral ferrites, backward waves emerge. However backward waves occur with both positive and negative helicities when propagating along the biasing magnetic field in chiral plasma.     

Propagation of Surface Waves on an Inhomogeneous Plane Layer

The permittivity of a plane layer is assumed to vary continuously as a function of distance measured from the surface. Solutions for the field distributions of surface waves on the inhomogeneous layer are developed with the WKB technique. Transcendental equations for the phase velocity are derived for TE and TM modes. These equations are solved most conveniently with the aid of phase-velocity graphs which are included. The accuracy of the solution is verified by comparison with the rigorous solution for an exponential inhomogeneity.     

瞬态电磁波在磁化等离子体中传播与散射的FDTD方法

本文从磁化等离子体中电子的广义运动方程出发，给出了一套ＦＤＴＤ计算公式，克服了卷积递归法不适用于直流入射以及小信号近似的缺点，其正确性由数值计算结果得到验证。     

Extraction of the Inversion and Accumulation Layer Mobilities in n-Channel Trench DMOSFETs

A new method to extract both the inversion and accumulation layer mobilities of electrons in n-channel trench double-diffused MOSFETs (DMOSFETs) is proposed and implemented for the first time. First, a model is developed for the on-resistance of the n-channel trench DMOSFET. This on-resistance model is fitted to the experimental data measured from an experimental n-channel trench DMOSFET by the method of linear least squares fitting. A very good fit is obtained such that the average percentage error between the model curve and the experimental on-resistance is less than$pm$1%. The fitting parameters obtained are used to calculate the inversion and accumulation layer mobilities as a function of a wide range of effective electric field. The calculated mobilities agree with those previously reported for conventional MOSFETs. The results are useful for optimizing the performance and reliability of the trench DMOSFETs.     

平面波导基模的衍射特性

在平面坐标系中简化电磁波的瑞利-索末菲标量衍射积分公式,推导出折射率对称阶跃分布的介质平面波导的基模衍射场分布的计算公式,给出由sinc函数形式描述的端口衍射场空间频谱和光强分布。首次提出介质平面波导衍射场存在中央亮条纹的概念,中央亮条纹的功率大于波导总功率的99.49%,中央亮条纹的最大空间频率介于π和1.5π,它可用于计算中央亮条纹的角半径。     

矩形贴片天线基模和高次模的研究和利用

对矩形贴片天线的基模和高次模进行了研究。研究表明,矩形贴片天线的基模和高次模都具有良好的辐射性能。据此提出了同时利用天线的基模和高次模来实现高性能的大频差双频段天线的思路。本文研究为实现性能优良的双频段大频差天线提供了一种新的思路。     

Spatial Distribution of the Amplitudes of Electromagnetic Waves Propagating in a Bounded Multilayer Structure with Periodic Irregularity

The step-by-step method is used for the analysis of propagation of electromagnetic waves in a multilayer structure of a finite length with periodic irregularities of the permittivity, permeability, and conductivity. The distribution of the wave amplitudes in the structure layers is considered and two its main types, sinusoidal and exponential, are revealed. Passbands and stopbands in frequency dependences of reflection and transmission coefficients are found. Parameters of these passbands and stopbands are determined by the combination of the periodicity of irregularities and the finiteness of the structure length. In the case of the tensor permeability, an additional stopband caused by gyrotropic properties of the magnetic medium is found. For the case of a conducting medium, the excess of the normalized amplitude of propagating waves over the unit level is considered and possible factors that cause its appearance are discussed.     

Proper and Improper Complex Waves of a Circular Two-Layer Screened Waveguide with an Axial Longitudinally Magnetized Ferrite Layer

In a two-layer circular screened waveguide with a longitudinally magnetized inner ferrite layer, the presence of different types of complex waves (CWs) both satisfying and not satisfying the energetic orthogonality condition is shown. The CWs are the solutions of a homogeneous boundary value problem, but, in the first case, the waves are energetically independent and, in the second case, they are associated with the source and indirectly coupled through it.     

Koch岛分形天线基模和高次模研究

主要研究了Koch岛分形天线的基模和高次模。研究表明,Koch岛分形天线高次模和基模都具有良好的辐射性能,且2种模式频比可达4.6∶1。基模的电流分布在天线的中间区域;高次模的电流分布在分形不规则的边界,形成强烈谐振。对Koch岛分形天线的基模和高次模的深入研究,为设计出性能优良的大频差天线打下了基础。     

Measurement of Layer Thickness and Permittivity Using a New Multilayer Model From GPR Data

The conventional method, i.e., the common middle point (CMP) method, has been used for many years for estimating the depth and permittivity of layered media from ground-penetrating radar (GPR) data. However, the CMP method results in noticeable errors in thickness and permittivity readings with the increase of antenna separation. To improve the measurement accuracy, a new mathematical model is presented, covering GPR measurement in one- and two-layer cases. In this model, we first check all the possible wave paths when the GPR signal propagates in the multilayer environment. We not only consider the effects from the air-ground interface but also introduce a ray-path-searching process in the GPR measurement using Fermat's shortest path law. The shortest path is then used in the process of GPR data inversion in order to calculate the depth and permittivity of each layer. Finally, we use the transmission-line matrix (TLM) method to simulate the propagation of a GPR signal in the multilayered formation. A time-sequence image that was produced by the finite-difference time-domain method has also been used to explain this presented model. By comparing the numerical simulation results with the measured results, it is found that the estimated layer thickness and permittivity by the new model agree well with the simulated results. It proves that the new model is more accurate and closer to the real measured situation.     

有液体层负载时压电薄板中兰姆波的传播特性

对有液体层风载时压电薄板中兰姆波的传播特性进行了理论研究和数值分析,给出了兰姆波相速、叉指换能器激发兰姆波的机电耦合系数与压电薄板及液体层归一化厚度之间的关系曲线,同时,还探讨了压电薄板的晶体取向和电边界件对兰姆波特性的影响。文中给出了结果,较全面地描述了有液体层负载时压电薄板中兰姆波的传播特性。     

Stability Analysis of Injection-Locked Oscillators in Their Fundamental Mode of Operation

Phase-lock stability of fundamental-wave injection-synchronized oscillators is investigated on the basis of a new time-domain approach. Starting from a quite general oscillator modeling and assuming single-frequency quasi-static operation, both exact and first-order approximate stability criteria are derived in a fully analytical form suitable for computer implementation. The examples worked out demonstrate good agreement of this theory with experimental observations available in the literature on multiple-tuned oscillators, whose behavior under large-signal injection was so far predictable only through graphical methods.     

宽温区MOSFET反型层载流子迁移率的模型和测定方法

首先介绍了宽温区 (2 7～ 30 0°C) MOSFET的阈值电压、泄漏电流和漏源电流的特点以及载流子迁移率的高温模型 ;进而给出了室温下 MOSFET反型层载流子迁移率的测定方法 ,最后提出了利用线性区 I- V特性方程测定宽温区 MOSFET反型层载流子迁移率的方法 ,并给出了测试结果     

On Slow and Fast Surface Waves Propagating on Plane Boundaries of Conducting Media with High Conductance. The Zenneck Wave

The regularities of transition of phase and group velocities from slow surface waves (whose velocities are below the light speed) to fast surface waves (whose velocities are above the light speed) on the plane boundaries of highly conducting media are investigated when the parameters of media vary. It is shown that the structure of waves does not change qualitatively in the case of this transition: the waves remain to be surface ones in contrast to surface waves of dielectric waveguides. The latter ones are transformed into leaking waves or their structure changes in a more complicated way in the case of such transition. A result relating, in particular, to the Zenneck wave is obtained.     

Depolarization, Scattering, and Attenuation of Circularly Polarized Radio Waves by Spherically Asymmetric Melting Ice Particles

The eccentric spheres model and an extended Mie solution are used to formulate scattering of a plane, electromagnetic wave by a single melting ice particle as well as by a horizontal layer of such particles. The incident wave is left-hand circularly polarized, whereas the scattered wave, as a result of depolarization by the spherically asymmetric particles, comprises left-hand and right-hand circularly polarized components. The Stokes parameters of the scattered wave are calculated throughout the melting process. Furthermore, radar observables of backscattering and depolarization, as well as the specific attenuation, across the melting layer are calculated. The numerical application manifests how the internal spherical asymmetry of melting ice particles is imprinted on backscattering, forward scattering, and depolarization. Moreover, it is shown how each part of the melting layer contributes to the attenuation and depolarization of the radio waves crossing that layer     

Mode Distribution and Bandwidth Characteristic of Arbitrarily Trapezoidal-Groove Guide for Millimeter Waves

The modes TE and TM of arbitrarily trapezoidal-groove guide are analyzed by using the mode-matching method. The mode TE₁₁ is the dominant mode of the trapezoidal-groove guide under different conditions. The bandwidth characteristic and the operation condition for the single dominant mode are discussed. The obtained conclusions are of very important significance in theoretical study and practical application of trapeziodal-groove guides for millimeter waves.     

Computer Analysis of the Fundamental and Higher Order Modes in Single and Coupled Microstrip

By means of finite difference methods, dispersion curves are obtained for the fundamental and higher order hybrid modes in both single and coupled microstrip. Structures of realistic proportions are investigated by the use of a graded finite difference mesh. Variational methods are used in deriving the finite difference equations. The higher order modes are found to be similar to LSM slab line modes. A spurious nonphysical class of solutions is found to exist in this and similar formulations, the characteristics of which are described.     

非线性阶跃型折射率光纤基模传播常数的变分公式

用变分法导出了克尔型（Ｋｅｒｒ—ｌａｗ）非线性阶跃型折射率光纤基模的传播常数公式结果表明，光束功率对基模的传播常数有显著影响。