Novel open-resonator for a quasioptical gyrotron

A new kind of open-resonator for a quasioptical gyrotron—an axisymmetrical quasioptical cavity of oblique roiation at arbitrary angle (AQCORAA)—is proposed. Using scalar diffraction theory and an approximate method, the field distributions in the AQCORAA are derived, and the influence of rotating angle on the field distributions is analysed. The stored field energy in the cavity is also obtained.     

Method of plane cross-section in the theory of axisymmetrical structures, containing the pieces of irregular coaxial and circular waveguides

The posibility to use the version of plane cross-section method for analisys of the axisymmetrical oversized waveguide sructures with one and two-coupled cross-section is considered. The solution of the methodical problem about principal wave scattering at the joint of coaxial and circular waveguides is presented.     

Kinetic theory of a novel carm oscillator with axisymmetrical quasi—Optical cavity of oblique rotation at arbitrary angle

A novel CARM oscillator with axisymmetrical quasi—optical cavity of oblique rotation at arbitrary angle (AQCORAA) is studied using the kinetic theory. By means of the method of local field expansion in the coordinates of the guiding centre and the Laplace transform, the beam—wave interaction power, starting current density and frequency shift are derived. The formulas presented here may have some potential applications for more further studies of the CARM oscillator with AQCORAA.     

Finite-difference analysis of dielectric-loaded cavities using thesimultaneous iteration of the power method with the Chebyshevacceleration technique

A numerical procedure using the finite-difference technique, simultaneous iteration based on the power method, and the Chebyshev-polynomial preconditioning is proposed to analyze dielectric-loaded cavities. The merit of this method is that no matrix inversions are invoked and the convergence rate of the power method is greatly accelerated by the preconditioning. The TE, TM, and hybrid modes in axisymmetrical cavities loaded with a rod or ring dielectric resonator are analyzed. For the hybrid modes, an H_r-H_z formulation is proposed. Accurate numerical results are obtained efficiently and no spurious solutions are found by the present method     

大功率晶体三极管温度场的激光全息干涉测量

采用激光全息干涉测量技术测量了轴对称型大功率晶体三极管温度场的全息干涉图;利用MATLAB数字图像处理工具箱对干涉条纹做了判读,并分别运用Abel法和小波变换法重建温度场。测量结果表明,温度场的空间分辨率为0．051cm,误差小于4．8％。     

轴对称场中折射率分布的再现方法

本文分析了轴对称场的光学特性，在此基础上，给出了一种计算轴对称场中折射率分布的新的再现方法。     

Determination of the Mode Content in Spurious Microwave Radiation of the Gyrotron with a Straight Axisymmetric Output

The method for determination of the mode content of a spurious microwave radiation of the gyrotron with a straight circular axisymmetrical output is discussed. As demonstrated, in the test task accuracy of this method is several percents. The experimental results on the determination of the mode content at the output of the coaxial gyrotron, operating on the mode TE _14.8 are in a good agreement with the theoretical calculations.     

非线性轴向不均匀自聚焦光纤轴对称场的变分解

本文用变分法求出了非线性轴向不均匀自聚焦光纤轴对称场的解析解。对于线性情形,变分解与其他文献的结果相同。     

二极管泵浦固体激光器热透镜焦距的数值模拟

理论分析了轴对称时,以泵浦光为标准高斯光束,在散热均匀情况下,激光晶体中的三维温度场分布,计算了热透镜焦距。利用Ansys数值,模拟了不同泵浦功率及不同泵浦光半径下,激光晶体中的三维温度场分布,并利用Matlab处理了温度数据,数值计算了热透镜对平行入射晶体端面的平面波产生相位畸变,描绘出热透镜焦距随半径的变化曲线。数值分析得出,热透镜焦距随径向发生变化,出射光波为非球面波,热透镜等效凹面镜不能用单一曲率半径描述,为非球面镜,并研究了泵浦功率和泵浦光半径对热透镜焦距的影响。     

Boundary element modeling of a capacitive probe for in situ soilmoisture characterization

There has been a need for accurate numerical modeling of a capacitive probe dedicated to the in situ characterization of soil moisture in measuring the dielectric permittivity of the soil. The objectives of the author's modeling were to understand the quantitative response of the probe, to optimize the shape of the probe, and to enable accurate calibration. In comparison with other numerical methods (such as the finite element method), the boundary element method appears straightforward and economical. The author presents a generalized version of this method in the case of an axisymmetrical geometry within the quasi-static limit. Numerical results are discussed and compared with the approximation of a lumped circuit     

用于探测激光等离子体冲击波的光纤传感器

利用探测光束通过轴对称流场时的偏折效应,设计了一种光纤传感器,并用于探测激光对材料破坏过程中在空气中激发的等离子体冲击波,获得了探测位置处激光等离子体冲击波流场折射率随时间的变化率.该方法适用于轴对称流场的瞬态测试,具有宽带和非接触的特点.     

A measurement technique for modeling the effects of feed support struts on large reflector antennas

A measurement technique is described in which frequency scaled models of struts are placed in the near-field region of an offset reflector. In this compact range environment the excitation of the strut model is by plane waves, as would be encountered in the axisymmetrical reflector situation. Far-field radiation patterns are recorded, with and without the strut model in place, and, because of the low sidelobe levels associated with offset reflector antenna systems, it is possible to isolate the far-field response of the strut model. This technique is particularly useful for determining the real effects of structures that are difficult to analyze mathematically, such as latticed struts or metallic geodetic radomes.     

A low-blockage dipole array reflector antenna feed for the lower microwave frequencies

An antenna is described which was devised as a feed for a small axisymmetrical paraboloid reflector at an operational frequency of just over 1 GHz. The antenna consists of a broadside array of two dipoles on a printed circuit board (PCB), joined by a common transmission line. Each dipole is backed by a small strip reflector. With this simple array, which has one central feed point, theH-plane radiation pattern can be varied independently of theE-plane pattern. In addition, the aperture blockage of the feed is small.     

The radiation pattern and impedance of offset and symmetrical near-field Cassegrainian and Gregorian antennas

Most Cassegrainian and Gregorian antennas have axial symmetry, in which case the subreflector and associated supporting members partially block the aperture. Consequently, relatively high sidelobes appear in the radiation pattern, and a reflection is produced in the transmission line of the feed. These undesirable effects can be largely eliminated using asymmetrical configurations. Here we compare axisymmetrical and offset near-field Cassegrainians and Gregorians; expressions for the reflection coefficient and increase in sidelobe level are given. The offset designs are found to have superior performance in both respects.     

Near-to-Near Transformation in Axisymmetrical Antenna Problems

Expressions for effective near-to-near (NTN) transformation of fields in structures of axial symmetry are presented. The results are applicable in the problems of axisymmetrical antenna feeds working in non-axisymmetrical reflector environment. The solution of the problem is based on an extension of the exact integration procedure for vector potentials of thin circular loop antennas, published previously by Werner. The Werner's procedure is used directly to calculate contribution of components of the equivalent currents at the Huygens surface surrounding the antenna. New formulas are provided for the contribution of and current components. The accuracy of the present approach is verified against the results obtained by direct numerical integration in the 3-D space. Asymptotic behavior of the NTN transformation for large distances is also compared to the known results of the near-to-far transformation.     

改进型任意倾角斜旋转准光腔

为了得到改进型任意倾角斜旋转准光腔（MAQCORAA）中的场的分布，用欧勒角来表示坐标系的变换，并采用积分方法替代矢量代数加法。MAQCORAA中场的分布是高斯形的，其峰值可以根据实际需要调整，这增加了电子与场相互作用区间的可自由度，得到的MAQCORAA场分布表达式更加简洁，将有利于其的线性和非线性分析。     

横流放电CO_2激光器气体热效应对光轴与横模的影响

本文讨论了横流放电CO_2激光器气体发热引起的折射率变化对光轴和横模的影响。计算表明,折射率变化的一阶小量会引起激光振荡轴位置和角度变化;折射率变化的二阶小量类似于轴对称放电管中的负透镜效应。这两种效应随着注入电功率、工作气压尤其是增益长度的增加而显著增大。     

激光穿孔中辅助气体动力学性能分析

通过基于结果的自适应算法对激光穿孔过程中的撞击射流场结构进行了计算.辅助气体与工件之间相互作用的本质过程可以描述为轴对称撞击射流过程,高压气体的轴对称撞击射流可以展示在高压状态下气体与工件之间的相互作用.气体射流与工件相互作用时,入射斜波与正激波发生直接接触和非接触的两种不同状态,分析了高压气体辅助激光切割第二个合理的加工区域的存在原因,加工参数对切口中气体动力学性能的影响,以及分析高压气体辅助加工能力随工件与喷嘴距离之间的关系.通常在入射斜波与正激波直接相互作用没有完成时,质量流率随工件与喷嘴距离变大而剧烈衰减,因此高压气体辅助激光切割时要尽可能保证工件与喷嘴的距离限定在合理的范围内.     

Offset Cassegrain Earth Station Antenna for the Japanese Domestic Satellite Communication System

Offset reflector antennas have advantages for communication systems because they are not severely subject to blocking. Difficulties mainly arising from structual asymmetries have inhibited the realization of an offset reflector antenna with a large aperture for commercial use. This paper describes the design of an offset Cassegrain earth station antenna for the Japanese domestic satellite communication system. Antenna measurements showed 76 and 69 percent aperture efficiencies at 20 and 30 GHz, respectively, less than -20 dBi wide angle directivity and an 18 K noise temperature in operating conditions. Performances are far superior to conventional axisymmetrical earth station antennas. The antenna was reassembled on a telephone office building after the measurements. The antenna gain was reconfirmed there, using the sun as a radio frequency source. Experiments show that the earth station antenna and a terrestrial antenna can be placed on the same building without serious interference.