Determining the polarization ellipse parameters of a multimode radiowave signal

A spectral-polarization method is proposed to determine the polarization-ellipse parameters of a radiowave signal in the wave front plane by analysis of three mutually orthogonal projections of the field vector. First, we calculate the complex Doppler spectra for the temporal variations of those projections. Then, these data are used to determine the polarization parameters of the electromagnetic wave for each spectral component. Formulas illustrating the proposed technique are presented, and the results of numerical simulation showing the possibility of practical implementation of the idea are given. Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences; Higher Aircraft Engineering Military School of Irkutsk, Irkutsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 4, pp. 324–332, April 1999.     

Study of the applicability conditions of the correlation function of a wideband multipath signal for estimating source coordinates

Using theoretical analysis and mathematical modeling, we study the dependence of the number of maxima in the correlation function of a wideband signal, whose parameters are related to the source coordinates, on the hydroacoustic conditions, the parameters of the receiver, and the signal/noise ratio.     

Determining a Skyrme-type effective interaction from realistic two-nucleon interaction

The Variational Monte Carlo (VMC) method is employed to determine characteristics of symmetric and asymmetric nuclearmatter. The realistic Urbana v14 nucleon-nucleon interaction potential of Lagaris and Pandharipande was used in the VMC calculations with addition of a phenomenological density-dependent term to simulate many-body interactions. A new Skyrme parameter set SKaan-U14 is found to consistently reproduce the characteristics of the nuclear matter obtained from VMC calculations. The properties of symmetric and asymmetric nuclear matter are calculated by the new Skyrme parameter set. The results obtained by using the new Skyrme parameter set are compared with results obtained by different Skyrme parameter sets in the literature.     

宽带声呐湖底沉积物分类研究

本文论述如何运用实际宽带主动声呐的回波信号识别湖底沉积物介质类型。五类湖底沉积层介质分别为:淤泥、岩石、孵石、沙、沙/砾石混合层。比较了等Q和等带宽两种子带能量频域特征提取方法,确认了等Q方法的优点。应用标准前馈BP人工神经网络结构,对五类湖底沉积层介质的平均正确识别率达到82.1%。     

Determining noise parameters of MESFET''s solely from their S parameters

A method for determining the noise parameters of MESFET's solely from their S parameters is presented in this paper. The enhanced Johnson noise, the diffusion noise, the thermal noise, the influences of bias condition, the effect of parastic resistances and the aftermath of package are all taken into consideration in the noise model. The calculating results of our method agree very well with the measured data. This method can be employed rapidly, conveniently, both at the wafer stage of device fabrication and to packaged devices.List of symbols a Thickness of the active layer - b Undepleted channel width - C, Cr Correlation coefficient - C_c Coupling capacitance - C_cg, C_cd, C_sg, C_sd Fringing capacitances - C_dc Drain-channel feedback capacitance - C_gs Gate-source capacitance - C_gd Gate-drain feedback capacitance - D The high field diffusion constant, =35cm²/sec - F_min Minimum noise figure - g_gn, g_dn Equivalent noise conductance - g_m Transconductance - I_ds Drain-to-source current - k Boltzmann's constant, =1.38×10^–23J/°K - L Gate length - L_dom Length of high-field domain - L_g, L_d, L_s Inductances of bond wire - N_D Doping density - q Electronic charge, =1.6×10^–19C - r_d Drain resistance - R_ds Output resistance of MESFET - R_g, R_d, R_s Resistances of bond wire - R_gs Ohmic resistance of a gate-source portion of a FET - R_n Equivalent noise resistance - S Scattering parameters - s Bias parameter, - S _io Spectral density - T Reference temperature - V_bl Built-in diffusion potential - V_ds Drain-source voltage - V_gs Gate-source voltage - V_nd Open-circuit noise voltage at drain - O _s Saturation velocity - W Gate width - x_i ith element of the equivalent circuit - Y_cor Correlation admittance - Y_i,j Four MESFET Y parameters corresponding to S parameters - Y_i,j MESFET Y parameters calculated from its equivalent circuit - Y_opt Optimum signal source admittance - _O Permittivity of free space - _r Realitive dielectric constant - Low field mobility - Transit time - f Narrow frequency interval Graduate student currently working toward the M.S. degree     

一种低信噪比测频技术

鉴于数字信号处理器(DSP)的迅速发展,本文提出了一种计算式测频方法。该方法可根据采样幅值计算出待测频率,并与自适应滤液器和参数平滑技术相结合,从而可在信噪比较低和存在其他线谱干扰的情况下实现信号频率的精测。计算机仿真和实际的工程使用已证明了它的有效性。该方法在水声和其他通信系统中具有一定的应用价值。     

Setup for taking the radiation spectra of wideband semiconductors

A setup is developed for measuring the spectra of wideband semiconductors (III nitrides) and related heterostructures. The setup makes it possible to trace the time distribution of the luminescence intensity at a fixed wavelength with a resolution of ±5 ns and a sampling rate of up to 10 MHz in the time interval from several microseconds to several hundreds of microseconds. Also, it plots the integral intensity of luminescence versus the wavelength. Precision measurement conditions are provided.     

Penetration of long strikers under hydrodynamic conditions with allowance for the material compressibility

The influence of compressibility on the fast penetration of long metallic strikers into different barriers at interaction speeds of up to 10 km/s is investigated. The investigation is based on the hydrodynamic theory of penetration. Compressibility-related corrections to Lavrent’ev’s rate and depth of penetration, which were obtained in terms of the concept representing the penetration process as collisions of ideal incompressible liquid jets, are estimated. The variation of these corrections with the interaction speed under subsonic and supersonic conditions is analyzed. If the compressibilities of the striker and barrier materials differ radically, the penetration depth disagrees with that predicted by the hydrodynamic theory (assuming the incompressibility of the materials) by 10–15%.     

Determining the order parameters of a nematic liquid crystal from the resonant Raman-scattering spectrum

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 6, pp. 938–944, December, 1989.     

Detection of the absorption spectra of water clusters under atmospheric conditions

The absorption spectrum of water clusters in the 5000–5300 cm^?1 range has been directly measured under laboratory conditions close to atmospheric conditions using the dynamical method for detecting water vapor in the metastable phase. It has been shown that detected absorption is primarily determined by water dimers.     

Determining the sea-roughness spectra from an optical image of the sea surface

An optical model of sea-surface imaging based on a two-scale presentation of sea roughness is developed. Using this model, an exact expression for the sea-surface image spectrum in diffuse sky light is obtained, which made it possible to estimate the nonlinear contribution of waves of different scales to the image spectrum. In particular, it is shown that the image spectrum is proportional to the wave tilt spectrum and the coefficient before the tilt spectrum is determined by the modulation of the short-wave contrast by long waves. Accuracy of determination of spectral contrasts of waves in surface-roughness anomalies (film slicks, internal-wave field, etc.) and accuracy of measurement of two-dimensional wave spectra from the sea-surface image spectrum are estimated. Examples of sea-roughness variability in the internal-wave field and examples of two-dimensional sea-roughness spectra are presented. All data were obtained by the optical method under full-scale conditions. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 1, pp. 53–63, January 2006.     

Size and average density spectra of macromolecules obtained from hydrodynamic data

It is proposed to normalize the Mark-Kuhn-Houwink-Sakurada type of equation relating the hydrodynamic characteristics, such as intrinsic viscosity, velocity sedimentation coefficient and translational diffusion coefficient of linear macromolecules to their molecular masses for the values of linear density M_L and the statistical segment length A. When the set of data covering virtually all known experimental information is normalized for M_L, it is presented as a size spectrum of linear polymer molecules. Further normalization for the A value reduces all data to two regions: namely the region exhibiting volume interactions and that showing hydrodynamic draining. For chains without intachain excluded volume effects these results may be reproduced using the Yamakawa-Fujii theory of wormlike cylinders. Data analyzed here cover a range of contour lengths of linear chains varying by three orders of magnitude, with the range of statistical segment lengths varying approximately 500 times. The plot of the dependence of [η]M on M represents the spectrum of average specific volumes occupied by linear and branched macromolecules. Dendrimers and globular proteins for which the volume occupied by the molecule in solution is directly proportional to M have the lowest specific volume. The homologous series of macromolecules in these plots are arranged following their fractal dimensionality.     

Determining film parameters from the dispersional dependence of waveguide polaritons

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 4, pp. 622–626, April, 1991.     

Transmission spectra and the effective parameters for planar metamaterials with omega shaped metallic inclusions

Planar metamaterials with omega shaped metallic inclusions were studied experimentally and theoretically. Our results show that when the incidence is perpendicular to the plane of the omega structure, the omega medium acts effectively as an electric resonator metamaterial. The stop band of the omega medium is due to the negative part of the electric resonance of the omega structure. The transmission band of the composite metamaterial (CMM) that is based on the omega medium is due to the strong positive part of the electric resonance of the omega structure. Consequently, the transmission band of the CMM does not coincide with the stop band of the omega medium. Furthermore, the transmission band of the CMM is a band with positive refractive indices. Our experimental and numerical results are in good agreement.     

Retrieval of the effective constitutive parameters from metamaterial absorbers

The equivalent medium theory of metamaterials provides a way to obtain their effective constitutive parameters. However, because of its non-reciprocity, the complexity of the electromagnetic coupling, and a metallic bottom layer, it has been challenging to retrieve them from a metamaterial absorber. In this paper, we propose a method without any approximation to obtain them, in which the non-reciprocity and the strong electromagnetic coupling are included. Compared with the three methods such as symmetric metamaterial method, asymmetric metamaterial method and metasurface method, our method can reveal the metamaterial absorber's electrical and magnetic resonance and show its electromagnetic coupling coefficients. To deal with a metamaterial absorber with a metallic bottom layer, four corners of the metallic bottom layer in the unit cell are removed, making it possible to retrieve the electromagnetic parameters. Surprisingly, these results show that the metamaterial absorber with a metallic bottom layer in our example operates in a negative refraction state at the half absorption frequencies, which helps further understand the absorbing mechanism of these metamaterial absorbers.