Accurate low-cost measurement technique for occupational exposure assessment of base station antennas

A new technique for near field measurements around wireless base station antennas is presented. Using these safety measurements the compliance boundaries of a base station are determined and compared with FDTD simulations. Excellent agreement is reported. The measurements are performed in a non-anechoic measurement site which results in a low-cost method.     

Procedures for noninvasive electromagnetic property and dosimetrymeasurements

Five different formulations are presented that can be used to determine local values of the complex permittivity, electric field, polarization current density, and rate of energy deposition, within an inhomogeneous dielectric object of arbitrary shape. These formulations were obtained from the matrix equations for moment-method solutions of the electric field integral equation. Implementation of these formulations requires knowledge of the shape of the object and the incident electric field, and measurements of the scattered electric field at a number of points external to the object. The use of a new type of model, with antenna arrays for measurements, has caused a substantial improvement in matrix conditioning. Results of numerical simulations using 21-cell models with high dielectric contrast (bone/muscle) suggest that all five formulations have sufficient accuracy to warrant experimental testing using cylindrical scatterers with transverse magnetic polarization     

多角度偏振成像仪系统级偏振定标方法研究

系统级偏振定标是多角度偏振成像仪(Directional polarization camera, DPC)研制过程中的关键环节,对于提高大气气溶胶和云相态等定量化探测应用具有重要意义。结合矩阵光学和辐射度学理论,建立了多角度偏振成像仪偏振响应定标模型,对关键影响参量进行定标。采用大口径积分球参考光源和分视场测量方法,消除了光楔平板对DPC三检偏通道视场非一致性的影响,实现了高频和低频相对透过率的高精度测量。采用傅里叶级数的分析方法,建立全视场起偏度的测量模型,消除参考光源偏振方位角绝对位置引入的测量误差,实现光学系统偏振特性的准确测量。采用可调偏振度光源和大口径积分球辐射源,开展了偏振定标精度的比对验证实验和精度分析。测试结果表明,全视场偏振定标精度优于0.5\%,自然光状态下的偏振定标精度优于0.05\%,验证了宽视场偏振遥感器偏振辐射响应定标模型的合理性,说明该系统级偏振定标方法可满足宽视场光学偏振遥感器的高精度偏振观测科学应用要求。     

弹光调制偏振Stokes参量测量及误差分析

为了更简便地实现Stokes矢量测量，采用一种工作在不同频率上的双弹光调制器，利用它的频率叠加对光进行调制，产生载有被测量的高频调制分量，通过锁相一次得到了适用于所有偏振态测量的4个Stokes分量，且进行了理论分析、仿真验证以及误差分析，即对相位延迟幅度、入射角等因素对测量结果的影响进行了分析。结果表明，该方法实现了只需测量一次便可测出偏振态的所有分量，为进一步工程实现提供了基本的理论支撑。     

Improved method for evaluating antenna performance in mobile environment with consideration of polarization and phase

The paper presents an improved method for evaluating antenna performance in a multipath propagation environment. It demonstrates, theoretically and experimentally, that by using polarization and phase terms of the incident field and the antenna system in the evaluation of the antenna effective gain (AEG), the AEG can be evaluated more efficiently as compared with the conventional method. First, a theoretical expression of the received power is given by using the open-circuit voltage at the antenna terminals, in which both the polarization and the phase of the incident field and antenna gain patterns are explicitly used. Secondly, a newly developed system for the measurement of field parameters, such as polarization and phase as well as amplitude, is introduced. Thirdly, incident field parameters measured in urban and suburban areas of Tokyo are described. It was confirmed that major incident waves were counted in up to five or six directions at a mobile terminal and their polarizations and phases were different depending on the direction of incidence. Also, measurement of the antenna gain patterns of the latest personal digital cellular handset at a talk position finds the dependence of the AEG on polarization and phase, which were significantly varied by the body effect. Finally, the AEG is evaluated based on the method introduced here, and its usefulness is compared with that of the conventional method.     

New method for measuring properties of nonhomogeneous materials bya two-polarization forward-scattering measurement

A novel method for measuring properties of grainy materials using a two-polarization scattering measurement combined with free-space phase measurement is introduced. The theoretical background of the measurement method is presented. Laboratory measurements of the depolarized scattering cross sections of white rice, green lentils, polystyrene beads, polyethylene beads, and their mixtures at 10 and 35 GHz using a vector network analyzer and two horn antennas are then presented. Results are compared with those based on the first-order multiple scattering theory. A low-cost set-up for industrial measurements is suggested     

Measurement and behavior of dual-polarization vegetation opticaldepth and single scattering albedo at 1.4- and 5-GHz microwavefrequencies

A measurement procedure has been developed and tested to determine horizontal and vertical polarization radiative transfer properties, i,e., single scattering albedo (ω) and optical depth (τ), of vegetation under field conditions. The procedure was applied to a wheat crop for a series of biomass densities. The measurements were done using two different radiometers (1.4 and 5 GHz) and for different view angles. The measurements and calculations indicated that the ratios of horizontal and vertical polarization radiative transfer properties (α=Γ_h/Γ_ν, α'=τ_h/τ_ν and β=ωh/ω_ν) are slightly dependent on view angle. However, no significant dependence on biomass density could be discerned     

天线极化特性的近场测量技术

针对天线极化特性如何在近场测量系统进行测试的问题,文中从实际工程应用出发,结合电磁场理论,基于椭圆极化波的分解理论,提出了利用线极化探头测量椭圆极化天线特性参数的方法。通过线极化探头进行两次正交的测量即可得到圆极化天线的方向图、轴比、倾角、增益等特性信息,也得到了线极化天线的交叉极化特性。     

一种外场动态全极化RCS测量标校方法

在外场条件下,获取动态目标全极化雷达截面(RCS)特性是电子对抗和目标隐身研究的需求.分析了目标RCS极化散射矩阵测量体制,研究了外场动态全极化RCS测量的标校方法,并在实际测量中对此方法进行了验证.该方法可为外场动态目标全极化RCS测量提供参考.     

Polarization Extraction in Planar Near-Field Phaseless Measurements

Near-field measurements typically require both amplitude and phase information to correctly predict the far-field. Unfortunately, there are situations in which the phase data is not available or impractical to obtain. That is why there has been a need for the development of phaseless techniques. Up until now, a number of remarkable solutions to this problem have been proposed by the researcher in different disciplines. Unfortunately, the complete vectorial representation of the field is not investigated in depth. The evaluated cases are usually linearly polarized and only the dominant polarization is investigated while the cross polarized field is usually neglected. This paper addresses the polarization issue in a two-component approach and then proposes a solution to the problem. A searching mechanism, for the incorporation of an appropriate initial guess, is integrated into the well-known, iterative Fourier technique (plane-to-plane) to enhance the algorithm response. Then, using two sets of measured orthogonal information data gathered by two linearly and orthogonally polarized probes, it is shown that with the aid of only a single point amplitude measurement, the polarization characteristics of the antenna can be extracted up to an inherent ambiguity of the right- and left-handedness. In order to have an assessment of the applicability of the proposed method, both linearly and circularly polarized antennas are simulated. Additionally, the method of extracting the polarization from the phaseless data is also verified through a bi-polar near-field measurement.     

Measurements and Prediction of the Polarization-Dependent Properties of Rain and Ice Depolarization

Relationships between rain and ice attenuation and depolarization at 19 GHz have been determined for linear incident polarizations ± 4 andpm 8degfrom vertical. These relationships are based on measurements made using beacon transmissions from a COMSTAR satellite. A technique is used to bound depolarization magnitude at any incident polarization from a depolarization magnitude measurement made at another polarization. This technique makes use of previous observations that depolarization is minimal at vertical and horizontal incident polarizations. The bounds are compared with the results from the COMSTAR measurements.     

Optical fiber characterization by simultaneous measurement of thetransmitted and refracted near field

An experimental setup is presented which permits, in a routine way for R&D purposes, simultaneous measurement of the transmitted near field at 1300 nm and 1550 nm, and the refracted near field at 820 nm. A new method for the calibration of the refractive index is proposed. The obtained accuracy for the refractive index is dn±0.0002. The reproducibility of measurements of geometrical parameters like the mode field diameter, the core and cladding diameters, and concentricity error, is ±0.1 μm. Measurements of the mode field as a function of polarization state for four different hi-bi fiber are presented     

Dynamic modeling of a horizontal washing machine and optimization of vibration characteristics using Genetic Algorithms

In this work, a 2D dynamic model of a horizontal axis washing machine is derived regarding the rotation plane in order to examine the vibration characteristics of the spin-cycle and improve the design proposing a new optimization scheme based on Genetic Algorithms (GA). The dynamic model is numerically simulated and the outputs are validated using experimental vibration data acquired from a test-rig including the drum and the motor of a horizontal-axis washing machine. The measurements are performed using piezo-transducers and a novel measurement scheme is used to obtain displacement values from acceleration data as well as estimating the instantaneous frequency of the rotation with appropriate signal processing. This study has two main contributions: (i) a new method for design improvement applying GA to optimization of vibration characteristics for the horizontal-axis washing machines, and (ii) a novel measurement method yielding the displacement in 2D and instantaneous frequency of vibration from acceleration data. While the GA is contributing to passive improvement methods in the field, the novel measurement method opens the way for low-cost diagnosis and active-vibration control of washing machines.     

New method to measure emitter resistance of heterojunction bipolar transistors

The in third-order intermodulation as a function of emitter current in a bipolar transistor is exploited to find emitter Ohmic resistance. The measurement can be carried out using only low-cost equipment and a scalar receiver. Results for an heterojunction bipolar transistor (HBT) are compared with those found using a vector network analyzer and a sophisticated extraction algorithm. The method is extended to simultaneously determine thermal resistance, R/sub TH/, and to obtain a most precise estimate of emitter resistance.     

Reflectometric measurements of PMD properties in long single-mode fibers

Polarization sensitive reflectometric measurements are effective tools for the characterization of polarization properties of optical-fiber link. The field of application of these techniques depends on whether they use a continuous wave source or a pulsed source to generate the probe signal. In the first case, reflectometric techniques may be successfully applied to perform single-end measurement of differential group delay and polarization dependent loss. In the second case—that is the case of polarization sensitive optical time domain reflectometry—the local birefringence of a single mode fiber can be measured and characterized. In this paper the theory and the applications of polarization sensitive reflectometric techniques are reviewed.     

Three ways to implement interfacial techniques: application tomeasurements of chromatic dispersion, birefringence, and nonlinearsusceptibilities

Depending on the spectal width of the source illuminating an interferometer, measurement procedures can utilize either the whole interferogram, or only the fringe envelope, or only the fringe quick oscillations. With an ultraband spectrum source, a simplified adaptation of the methods of Fourier transform spectroscopy yields the variations of the test-fiber propagation constant over the whole wavelength-interval of the source. Chromatic dispersion can then be computed from a single interferogram. With narrower spectrum sources, only the fringe envelopes are utilized and yield measurements of mode delay, with application to chromatic and polarization mode dispersion. In this case, however, interferograms at several wavelengths are necessary. With even narrower spectrum sources, the fringe quick oscillations provide measurements of phase shifts, related to changes in the mode propagation constant, when outside perturbations are applied to the test fiber. A direct method for measuring the third-order nonlinear susceptibilities is discussed. In this case the outside perturbation is an intense pump laser field     

Six-Port Interferometric Technique for Accurate $W$ -Band Phase-Noise Measurements

An innovative six-port (SP) phase-noise measurement technique for millimeter-wave high-power sources is proposed in this paper. Simulation results using a 94-GHz rectangular waveguide SP circuit model validates the measurement principle for both millimeter-wave oscillators and amplifiers. Phase-noise measurement results of a 100-W extended interaction Klystron amplifier are presented and discussed. Compared to conventional methods, this new method allows accurate low-cost phase-noise measurements.     

Algorithms for estimating the complete group of polarization invariants of the scattering matrix (SM) based on measuring all SM elements

The procedure for estimating polarization invariants of the backscattering matrix in horizontal-vertical basis is considered for radar observation of arbitrary nonreciprocal objects. Two polarization invariants are added to the well-known six Huynen-Euler invariants. These new invariants (nonreciprocity angle and difference in absolute phases of the symmetric and antisymmetric parts of the scattering matrix) describe the nonreciprocal properties of the object itself. With the simultaneous measurement of all eight quadratures of the scattering matrix elements, the closed-form expressions for calculating the eight polarization invariants are given. The derived expressions are the starting point for complete estimation of the polarization properties of arbitrary radar objects with a nonsymmetric scattering matrix. The given approach can be used to study various polarization effects in remote radar sensing of artificial and natural objects, and also to simulate polarization measurement processes and estimation errors caused by the measurements of scattering matrix elements at different instants.