Electrodynamic analysis of a Pendry lens

Excitation of a magnetodielectric plate with the parameters ? → ?1 and μ → ?1 by an elementary electric dipole is considered. The behavior of the wave field is investigated in the case when the values of the constitutive parameters approach the singular point ? = μ = ?1 along the curve ?μ = 1. A condition is established under which the transverse dimension of the field in the focal plane of the lens is smaller than the diffraction limit. The dimension of the spot is expressed in an explicit form. It is shown, that, in the situation considered, the effect of longitudinal focusing is absent.     

The resonance properties of the near field in finite thin Veselago and Pendry lenses

The problem of excitation of a finite thin plate made from a metamaterial with the electrodynamic parameters ? _r ?? ?1, ?? _r ?? ?1 and ? _r ?? ?1, ?? _r = 1 by a point source is considered. Resonance phenomena in the near field of plates are found that are caused by the interaction of the formed surface waves. It is shown that the near field of the plate has the form of standing surface waves localized near wide faces of the plate, and the high Q factor of the observed resonances leads to the extremely strong dependence of the excited near-field amplitude on the electric and geometric parameters of the plates.     

The resonance field of a radiator surrounded by an inhomogeneous spherical plasma shell

The field of a radiator located in free space and surrounded by an inhomogeneous spherical plasma shell whose permittivity passes through the point ? = 0 is found and investigated. It is shown that the behavior of the permittivity in the vicinity of the value ? = 0 substantially affects the formation of the source field. The resonance properties of the obtained solution to the problem are studied for a sphere of a small electrical dimension.     

Effective electromagnetic and chiral parameters of chiral composite material

The effective parameters of chiral composite are studied using a simple model, that is, randomly oriented non-interacting wire helices embedded in a nonchiral host medium. It is found that both the effective permittivity ? and permeability μ are independent on the handedness of the chiral objects while the effective chirality admittance ξ is dependent. It is also found that when the ratio of the radius of the chiral helix to its pitch is about 0.23, maximum chirality admittance is achieved. The effective parameters of equichiral sample are also discussed.     

The reconstruction of the relative phases and polarization of theelectromagnetic field based on amplitude measurements

The problem of determining the relative phases among the components of a monochromatic electromagnetic field at a single point based on amplitude measurements only is addressed. The following questions are answered: (1) How is the phase information reconstructed from amplitude measurements? (2) Do amplitude measurements contain enough information to reconstruct the phases uniquely? (3) How many amplitude measurements are required? and (4) In what directions must the amplitude measurements be taken to ensure that the reconstructed phases are unique? To answer these questions, a more general problem in n dimensions, the special case where n=3 being the solution to the above problem, is proposed and solved     

The effect of chirality on the existence of backward waves in metamaterials made from resonance planar chiral elements

Artificial media made from lattices of resonance planar chiral elements (RPCEs), such as planar double open rings and plane spirals, are considered. The effect of chirality on the electromagnetic properties of such media is investigated theoretically. It is shown that, when RPCEs are identically oriented, backward waves do not propagate in the medium, although there is a region where permittivity ? and permeability μ are negative simultaneously. However, such a metamaterial exhibits chirality and, hence, the refractive index turns out to be imaginary even when energy dissipation is disregarded. It is found that a medium with the opposite orientation of neighboring RPCEs is nonchiral; in such a medium, the resonance property of ? and μ is retained; the refractive index is real; and backward waves are present at frequencies at which both ? and μ are negative. For these media, it is found that there are regions where the directions of propagation of the wave energy and phase coincide (right-handed passbands), a region where these directions are opposite (left-handed passbands), and regions of evanescent waves.     

Reliability of a quasi-redundant electronic system with “standby” in the main unit

The reliability of a quasi-redundant electronic system with a standby in the main Unit has been studied. It is assumed that failure and repair time distribution of each unit is negative exponential with parameters γ and μ respectively. Laplace transforms have been used in solving the difference-differential equations.     

Effect of rain in the near field of an antenna

The effect of rain on the field at a point irradiated by a microwave antenna is found, in contrast with previous work, to be effectively independent of the parameters of the antenna. The standard Fresnel zone criterion for the `active rain volume? has been extended to treat rain in the near field of the antenna.     

Two-frequency resonance scattering by finite thin metamaterial plates

A finite thin plate made from a metamaterial with negative values of permittivity ? and permeability ?? is considered. The 2D problem of excitation of the plate by a cylindrical wave is numerically investigated. It is found that the frequency dependence of the excited near field has two high-Q resonances closely spaced in frequency and that the constitutive parameters have values close to those that lead to triple (double) degeneration of a surface wave in an infinite plate. The near and far fields at the resonance frequencies are calculated.     

Definition of parameters values of sinusoidal signal,distorted by unknown pulses

In this paper a problem of definition of sinusoidal signals parameters distorted by unknown pulses is considered. It is supposed that shape, quantity and other parameters of pulses a priori unknown, but their total duration is less then an observation interval. It is given a criterion that this problem solution is achieved at the point of a minimum of a functional “duration residual” between known data and mathematical model.     

Diffraction of a cylindrical wave by a perfectly conducting cylinder enclosed in a metamaterial shell with a negative refractive index

The problem of diffraction of a plane (cylindrical) wave by a perfectly conducting cylinder enclosed in a metamaterial shell is rigorously solved. The influence of the geometric dimensions of the shell, the value of the negative refractive index of the metamaterial medium, and the position of a cylindrical wave source on the field structure in the near zone of the scatterer is investigated. It is found that, in the quasi-optical range of the problem parameters, this structure does not exhibit ideal focusing. It is shown that, there are two types of caustics inside the shell. The first type is related with rays reflected by the surface of the interior cylinder and has one cusp point, and the second type is formed by the geometric-optics rays that are refracted by the outer boundary of the shell and do not fall on the surface of the interior perfectly conducting cylinder. The spatial distribution of the total field amplitude and of the equal-amplitude lines in the near zone of the scatterer is reported. The obtained numerical results are correctly interpreted from the physical viewpoint.     

Infrared Texture Simulation Using Gaussian-Markov Random Fields

Infrared battlefield simulation is a most important subject today to test infrared weapons. The reality and details of simulated scenes are always relied on the infrared textures. A texture is considered to be a stochastic, possibly periodic, two-dimensional image field. A texture model can be described as a mathematical procedure. Markov random field(MRF) model is a famous model to synthesize the visible textures of various kinds. In this paper, the Gaussian-Markov random fields(GMRF) are firstly used to sample the distribution of temperature field on the surface of terrain. And the Planck's radiation law is applied to calculate the emittance in the bands of 3～5 μ m or 8～14 μ m. The emittance distribution of the terrain can be normalized and colored by the range of 0 to the gray levels decreased by 1. Then an infrared texture is generated by GMRF by given a set of certain parameters.     

NMOS器件ESD特性模拟

NMOS管I-V曲线在ESD(electrostatic discharges)脉冲电流作用下呈现出反转特性,其维持电压VH、维持电流IH、触发电压VB、触发电流IB以及二次击穿电流等参数将会影响NMOS管器件的抗ESD能力。文章通过采用SILVACO软件,对1.0μm工艺不同沟长和工艺条件的NMOS管静电放电时的峰值电场、晶格温度以及VH进行了模拟和分析。模拟发现,在ESD触发时,增加ESD注入工艺将使结峰值场强增强,VH减小、VB减小,晶格温度降低;器件沟长和触发电压VB具有明显正相关特性,但对VH基本无影响。最后分析认为NMOS管ESD失效主要表现为高电流引起的热失效,而电场击穿引起的介质失效是次要的。     

数字电视显示参数分析

分析数字电视的幅型比、图像尺寸、分辨率等显示参数，说明它们与临场感、视场角等视觉特性的关系。在模拟电视向HDTV的过渡期内，从显示参数角度分析现有电视接收设备可能会出现的问题。     

Least squares estimation of 2-D sinusoids in colored noise: asymptotic analysis

This paper considers the problem of estimating the parameters of real-valued two-dimensional (2-D) sinusoidal signals observed in colored noise. This problem is a special case of the general problem of estimating the parameters of a real-valued homogeneous random field with mixed spectral distribution from a single observed realization of it. The large sample properties of the least squares (LS) estimator of the parameters of the sinusoidal components are derived, making no assumptions on the type of the probability distribution of the observed field. It is shown that if the disturbance field satisfies a combination of conditions comprised of a strong mixing condition and a condition on the order of its uniformly bounded moments, the normalized estimation error of the LS estimator is consistent asymptotically normal with zero mean and a normalized asymptotic covariance matrix for which a simple expression is derived. It is further shown that the LS estimator is asymptotically unbiased. The normalized asymptotic covariance matrix is block diagonal where each block corresponds to the parameters of a different sinusoidal component. Assuming further that the colored noise field is Gaussian, the LS estimator of the sinusoidal components is shown to be asymptotically efficient.     

Optimal modulation for known interference

We present a symbol-by-symbol approach to the problem of canceling known interference at the transmitter in a communication system. In the envisioned system, the modulator maps an information symbol (taken from a finite alphabet) and an interference symbol (from the complex field) onto a transmitted constellation point. Our scheme is based on joint optimization of a modulator and demodulator, subject to a constraint on the average transmit power. The demodulator picks the information symbol (as a function of the received symbol) that minimizes the average error probability. We emphasize that our focus is on transmission in a single (complex) dimension, and hence the proposed technique is a ?modulation? rather than a ?coding? scheme. We illustrate that the new scheme outperforms Tomlinson?Harashima precoding, which is a classical but suboptimal solution to the one-dimensional known-interference precoding problem. In our simulations, the new approach is able to perform close to the no-interference bound.     

基于遗传算法的多关节三维扫描仪系统参数定标

介绍了多关节三维扫描仪坐标测量原理,分析了结构参数误差模型,指出多关节三维扫描仪定标实质上是一个优化过程,提出了利用遗传学原理进行定标,并给出了算法,实验结果表明该算法能有效地确定扫描仪的结构参数。     

Specific features of the charge carrier mobility in nanowires in transverse electric and magnetic fields

The effect of an electric field E orthogonal to the quantum-wire axis and a magnetic field H (H ⊥ E, H ‖ E) on conductivity is studied within the context of the parabolic potential model. It is shown that, if the interaction of charge carriers with the rough surface of the nanostructure is taken into account, the charge-carrier mobility μ as a function of increasing E is described by an unsteady oscillating curve. A physical interpretation of such behavior of μ with E is proposed. The specific features of mobility in a transverse magnetic field are discussed.     

IR photodetectors in the range of λ = 1.5–8 μm, based on silicon with multicharged nanoclusters of manganese atoms

It is demonstrated that infrared photodetectors based on silicon with multicharged nanoclusters of manganese atoms can be designed that operate in the wavelength range of ?? = 1.55?C8 ??m. Photodetectors fabricated on such materials have the following parameters: a spectral sensitivity range of ?? = 1.55?C8 ??m, an operating temperature range of T = 77?C250 K, an optimal electric field of E = 5 V/cm, an optimal size of V = 3 × 2 × 1 mm³, a sensitivity threshold of S = 10^?9 W/cm², and a response time of ?? < 10^?6 s.     

Characteristics of near field of the horizontal vibrator located above a square screen

The 3D vector problem concerned with the diffraction of the horizontal half-wave vibrator field by a perfectly conducting and infinitely thin rectangular screen is solved during observations at a finite distance from the vibrator. The technique for calculating the diffracted field, which is based on the laws of geometric diffraction theory and uniform diffraction coefficients obtained from the rigorous solution to the problem of the diffraction of the field of a Hertzian electric dipole at the edge of a perfectly conducting semiplane, is proposed. Fast-acting programs for calculating and analyzing the amplitudes and phases of the components of diffracted and complete vibrator fields in the entire space of observation angles at the set distance of the observation point from a rectangular screen and along the normal to the screen under changes in the distance between the screen and the observation point are developed. The character of the transformation of the spatial amplitude distribution of three field components depending on removal of observation point from an antenna is studied. It is shown that the distance to the far field zone of the investigated radiating system exceeds two wave lengths.