Sensitivity of Homogeneity Mapping of Semiconducting Wafer Using Millimeter Waves

The homogeneity mapping by measuring the phase or the amplitude of millimeter wave reflected from or transmitted through the semiconducting wafer is considered. The sensitivity of the conductivity homogeneity mapping is determined and conditions at which conductivity inhomogeneities can be distinguished from dielectric constant inhomogeneities are established.     

Nondestructive Material Homogeneity Characterization by Millimeter Waves

Millimeter wave bridge technique for nondestructive material homogeneity characterization is described. The idea of this technique is the local excitation of millimeter waves in testing material and the measurement of the transmitted amplitude and phase in it different places. Some results of the homogeneity measurements for the dielectric substrates are presented.     

Waveguide Filter on Base of Dielectric the Bragg Structure for Millimeter Waves Applications

It is considered and offered the waveguide band elimination filter with the working mode H₁₀ that can be used in millimeter waves devices such as up, down- converters, mixer, etc. The characteristics of the filter was calculated by using analogy in electromagnetic the waveguide propagation and optical the wave propagation in the medium with the specific refractive index N. This conception can be applied for party-filled waveguide in the case when the Brillouin decomposition of the waveguide waves into plane waves is correct and the transformation of the incident (propagating) mode into other the mode types is absent.In this work were calculated the spectrum energy transmittance T(f) in the filter stop band and the wavelength ₀ in the center of this band using the characteristic equation obtained in the result of theoretical consideration. Theoretical results are compared with experimental measurements.     

Computation of the Backscattering Power Density for Rainfall in Millimeter Waves Band

The size distribution and canting angle distribution for non-spherical rain drops are taken into account. Utilizing the Muller matrix, the backscattering power densities are computed at different rain rate and different polarization in millimeter waves band, according the rainfall condition in Xi'an, China. Finally the results obtained are discussed.     

Analysis for Transmission Properties of Arbitrarily Trapezoidal-Groove Waveguide for Millimeter Waves

In this paper, the transmission properties such as the dispersion and attenuation characteristics for the dominant mode of the trapezoidal-groove waveguide with arbitrarily inclined angle are analyzed and discussed by using the mode-matching method. Some calculated results are in very good agreement with the published data. The obtained conclusions are of important significance in theoretical studies and actual applications of trapezoidal-groove waveguides for millimeter and submillimeter waves.     

Impedance Characteristics of Closed Elliptic-Groove Waveguide for Millimeter Waves

A characteristic equation and impedance characteristic for the dominant mode of closed elliptic-groove guide have been analyzed and discussed by using the mode-matching method. The reference size of the closed elliptic-groove guide for the good impedance matching with rectangular guide in actual application is given. The obtained conclusions are of important significance in theoretical studies and actual applications of closed elliptic-groove guide for millimeter waves.     

Transmission Properties of Closed Trapezoidal-Groove Guide for Millimeter Waves

The transmission characteristics of the mode TE₁₁ for a new type of closed trapezoidal-groove guide with arbitrary inclined angle are analysed in detail with the mode-matching method in this paper. The calculated results are in good agreement with the experimental values in the published reference. The dispersion of the closed trapezoidal-groove guide is very low. The relationships of the cut-off wavelength and the attenuation constant with the structural sizes of the closed trapezoidal-groove waveguide are also obtained. The given results have very important value in study, design, manufacture and application for closed trapezoidal-groove waveguide.     

The Improvement of PML Approach for the Calculation of Microwave and Millimeter Waves Circuit

The improved PML absorbing boundary condition have been introduced in this paper. The reflection coefficient of the absorbing boundary condition is less than the reflection coefficient of Berenger's PML algorithm. And in order to validate the theory and its effectiveness, We have applied the absorbing boundary condition to the calculation of microwave and millimeter waves circuit and get its reflection coefficient S ₁₁. The numerical result is shown in this paper.     

Variations of Free Volume of the Air Abundant in the Water by the Millimeter Waves of Low Intensity

We have found that low power millimeter electromagnetic radiation causes an increase in the volume pertinent to the free air abundant in water. This change is caused by the transition of some part of the dissolved air into a bubble state under decreasing dissolubility of the gas due to its thermal heating by the waves. The increase in the free air may occur only under those conditions when there is no convection in the liquid, i.e. in the case of irradiating by means of low-intense waves.     

The Effects Induced by Turbulence and Dust Storms on Millimeter Waves

Dust storms and turbulence consist of a random medium system, its effects on milimeter waves propagation are studied. Attenuation of millimeter waves, its phase shift and cross- polar discrimination are presented. Results show that dust storms mainly effects XPD and phase shift of millimeter waves, turbulence chiefly produces attenuation, in mediocre fluctuation.     

Normal Metal-High Tc Superconductor Point Contact Properties At Millimeter Waves

Experimental results of the response of a metal-high T_c superconductor (BSCCO-2212) point contact to millimeter wave radiation both at room and liquid nitrogen temperatures are presented. Measurements were carried out with and without bias current. An unexpectedly large response signal was observed when the bias current was applied. This effect is explained by the heating of the interface area below the tip of the metallic probe by the alternating current of the millimeter wave. The response signal was compared with that obtained using a Schottky diode.     

Transmission Modes of Closed Elliptic-Groove Waveguides for Millimeter Waves

In this paper, a new type of horizontal-flat and vertical-flat closed elliptic-groove guides is firstly presented. The field components and characteristic equations for some main transmission modes of the closed elliptic-groove guides are derived by with the help of the mode-matching method and Mathieu function. The variations of the cut-off wavelengths along with eccentricities, widths and lengths of the parallel plates for a number of lower order transmission modes of the closed elliptic-groove guides are also analysed in detail. The calculated results in good agreement with ones in the relevant references are of very important values in theoretical researches and actual applications of closed elliptic-groove guides for millimeter and submillimeter waves.     

Analyzing Semicircular Groove Guide with the Conformal Mapping Technique

Semicircular groove guide is a kind of waveguide for millimeter waves. In this paper, a conformal mapping technique is used to analyze it. Several semicircular groove guides are calculated with the method. It is shown that their cutoff wavelength calculated by the method are very close to those calculated by the transverse resonance method.     

On Causes of Biological Efficiency of Low-Intensive Millimeter Waves

The process of the ions transport through the biological membrane is considered. A role of air microbubbles efficiently mixing a near-membrane liquid layer in the presence of a temperature gradient is pointed out. These circumstances result in lowering an energy barrier height of the transmembrane ion-transport. It is shown that even low-level irradiation by the millimeter waves creates the temperature gradient, which is enough for effective mixing of near-membrane liquid's layer. It is demonstrated that a process of restoration an equilibrium air-distribution in the intercellar medium after ceasing the microwave irradiation proceeds according to the diffusion mechanism, i.e. rather slow.     

On Mechanism of Influence of Low Intense Millimeter Waves on Air Content in Water

The two-stage mechanism is offered, on which the millimeter waves rises concentration of free air in water. At first, millimeter waves localize heating in a volume of the sample, creating supersaturated concentration of the dissolved air in a fluid. Then superfluous air diffuses in embryonic microbubbles present in a fluid. The experimental data confirm the mechanism suggested.     

Change of Volume of Air Dissolved in Water Imposed to Millimeter Waves of Low Intensity

We discuss an experimental evidence for a decrease in the volume of air dissolved in water caused by millimeter electromagnetic waves of low intensity. The changes obtained were much greater than the expected conditioned by a pure thermal effect. The result observed is explained by air bubbles that take an active part in a mechanism of withdrawing dissolved air from water. The variation of restoring the dissolved air volume up to an equilibrium level after ceasing irradiation of water by millimeter waves was investigated as well.     

Millimeter wave investigation of dielectric cylinders absorption cross-section by resonant method

A new millimeter wave resonant method for determination of absorption cross-section of vegetation stalks is given. The method is developed for study of vegetation stalks absorption cross-section as a function of their moisture content, orkR parameter (k is a wave number, R is a stalk radius) in millimeter wavelengths band. ModesE _01p of a cylinder resonator are employed for such measurements. Dielectric permittivity and loss tangent of a sample can be found by measuring a frequency shift andQ- factor changes of the resonator. Absorption cross-section of a sample is then calculated using a formula obtained in our theoretical study. This formula can be written analytically as a result of rigorous solution of the related diffraction problem (scattering of a plane electromagnetic wave by cylinder with complex dielectric permittivity if stalk radius is less then 0.5 mm for the wavelength of 8 mm).Results of this investigation may be used in creating electrodynamical models of media containing cylindrical stalks of plants, in direct measurements of some canopy parameters, transmission properties measurements of vegetation canopies etc.     

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.     

基于子孔径拼接技术的大尺寸光学材料均匀性检测系统

为实现大尺寸光学材料折射率均匀性的高精度、低成本检测,提出一种基于子孔径拼接技术的干涉绝对测量方法,并研制了一套由Zygo干涉仪、五维气浮调整平台、子孔径拼接软件、计算机等组成的测量计算系统。待测件安放在精密的五维气浮调整架上,通过移动调整架来对各个子孔径区域进行精密检测,再利用子孔径拼接软件自动拼接计算出全口径待测件的光学均匀性分布。对直径为300mm的石英待测件进行了口径为180mm的8个子孔径拼接检测实验,并将拼接所得结果与全口径干涉仪直接测量的结果进行了分析和比较,波面峰谷值相对误差为0.21%,光学均匀性值相对误差为0.23%,精度与大口径干涉仪直接测量的精度相当,实现了绝对检验下的平面类波前子孔径拼接技术的实用化。整套系统集光、机、电、算于一体,操作简便,测量精度高。     

Scattering of Millimeter Waves from Acid Rain

A theoretical investigation of scattering characteristics of millimeter waves from acid rain is conducted using the method of vector spherical function expansion. The particles of acid rain are considered as the double-layered spheroid. The method is used to derive an analytical solution to the problem of scattering of millimeter waves by a coated dielectric spheroid. The normalized bistatic cross section versus scattering angle for the acid raindrop is calculated at frequencies of 35 GHz and 94 GHz. This is the first part of our study scattering characteristics of millimeter waves from acid rain.