Quasi-optic excitation of an open resonator

A technique and results of solution of the problem on plane-wave excitation of an open quasioptic resonator and a quasi-optic resonator located in an oversize waveguide are presented. Structures with various shapes of the mirror are investigated. The results obtained with the help of the proposed technique are compared with the results obtained by means of an approximate approach.     

Cross-shaped dielectric resonator antenna analysis using conformalfinite difference time domain method

A cross-shaped dielectric resonator antenna, designed for circular polarisation, is analysed via the conformal finite difference time domain technique. The conformal technique, which can handle canted surfaces that do not conform to the Cartesian system of co-ordinates, is used to generate accurate results with a relatively coarse mesh, e.g. it is shown that the conformal FDTD offers a 2:1 advantage over staircasing, without compromising accuracy     

一种在时域调谐带通滤波器的新方法

文章介绍了一种基于滤波器S11响应的时域分析的调谐方法。这种方法可以区分谐振器和耦合孔各自产生的时域响应，可以用来指导调节谐振器和耦合系数，得到所需的滤波器响应。通过这种方法还可以观察滤波器内部各元件间是如何相互作用的。     

Note on the radiation associated with the excitation of an open resonator

Open resonators have a number of possible applications at microwave frequencies; the very high Q factor obtainable is one attraction. Coupling to the resonator usually takes place through small coupling holes in the mirrors. An important practical question is to what extent radiation of energy out of the resonator by these holes limits the Q factor obtainable. In this letter a very simple formula is derived. The effect is shown to be very small.     

Microwave measurements on dust, using an open resonator

The measurement at 10 GHz of the refractive index and tan ? for fine powders, sparsely distributed in the atmosphere, is reported. The realisation of a uniform density of particles within a large resonator is discussed.     

High-order azimuthal modes in the open resonator

Using complex-source-point method, it is shown that the linearity polarised TEM01 azimuthal modes from conventional beam wave theory should be replaced by two other sets of azimuthal modes with different polarisation configurations. The difference in frequency for the same-order mode for these two sets is calculated and verified by experiment.     

Measurement of the extinction cross-section of dielectric spheres using an open resonator

The measurement of the extinction cross-sections at microwave frequencies for a set of spheres made of low-loss dielectric material is reported. Measurements were carried out at Q-band using a microwave open resonator. Results are compared with calculated values derived from Mie's theory.     

Application of an anisotropic perfectly matched layer absorber for open boundary truncation in the multiresolution time domain scheme

We apply an anisotropic perfectly matched layer (APML) absorber for open boundary truncation in implementation of the multiresolution time domain (MRTD) scheme. We develop an APML update algorithm to handle a general APML region in the MRTD formulations with the content of the leapfrog algorithm applied in the conventional finite-difference time-domain method. We also discuss the boundary truncations for both perfectly electric conductor (PEC) and perfectly magnetic conductor (PMC) walls using the image techniques. We validate the algorithm by analyzing various guided wave and antenna structures. It is found that the APML performs well for absorbing electromagnetic waves in the MRTD algorithm.     

Improvements in the beam-wave theory of the open resonator

It is shown that electromagnetic perturbation theory can be used to improve the well known beam-wave formula for the resonance frequency of an open resonator. A simple case has been worked out in detail. A connection between the perturbation method and a variational formula is indicated.     

开放系统的无粒子数反转激光的时间演化分析

对开放的V型三能级系统,通过微分方程的数值运算,分析了该系统的无粒子数反转激光(laser without inversion, LWI)产生的机制,讨论了探测场和驱动场的失谐、驱动场的Rabi频率、粒子初始状态对系统LWI时间演化的影响.结果显示:驱动场耦合的两个能级上的粒子数分布以相同的频率振荡,位相差π;在探测场和驱动场皆共振(⊿=⊿<,o>=0)时,原子对探测场色散的响应为零,双光子相干项ρca是实量;驱动场的Rabi频率Ω增大时,增益、相干项和粒子数差的振荡周期减小;粒子数的初始状态主要影响增益、相干项和粒子数差的振荡幅度,并不影响最后的稳定状态.     

Low power measurements of the quality factor of an open resonator with stepped mirrors

Open resonators in which both mirrors have a central step have been predicted to exhibit mode selection properties. This is advantageous for the design of quasi-optical gyrotrons. Quality factor measurements of a 36 cm resonator at 120 GHz are presented and compared with theory. Although the effect of the step is clearly seen, the quality factor Q of the resonator is lower than that predicted.     

New technique for measurement of total scattering cross-sections using an open resonator

It is shown that, for obstacles having a ceprtain symmetry, the cross-section for absorption and scattering can be determined by measuring under prescribed conditions the Q factor of an open resonator into which the obstacle is introduced.     

Approximation for the response of capacitively loaded transmission-line networks in the time domain

An approximate procedure for determining the time response of networks containing transmission lines terminated by lumped capacitive and resistive elements is outlined. It is possible to reduce the capacitively loaded system to a simpler form with purely resistive loads which can be handled using a graphical method.     

Transient response of an infinite cylindrical antenna

A simple analytical formula derived from Wu's exact solution for the transient response of an infinite cylindrical antenna is found to be extremely accurate. Existing results from other numerical schemes are also compared to Wu's solution and found to be in good agreement.     

Fine tuning of a millimetre-wave open resonator

The discussion is of a method of fine tuning and frequency setting of a millimetre-wave open resonator, which represents an improvement over the conventional method of tuning by moving one mirror. The important features of the mechanism are examined. A theoretical analysis of the situation supports the experimental results.     

Determination of scattering widths of a long thin wire using an open resonator

Using an open-resonator method, the scattering widths of a set of thin copper wires have been measured. The results are in agreement with theory to within about 9%.     

Excitation of an open resonator coupled with a waveguide via a slot in a mirror

A technique and results of the solution of the problem on excitation of an open mirror resonator coupled with a waveguide via a slot in one of the mirrors are presented. The effect of the coupling slot on the radiation loss is analyzed. The results obtained with the help of a rigorous approach and approximate techniques are compared.     

Transient response of an inhomogeneous MOS transmission line

Analytical solutions for charge transport in inhomogeneous MOS transmission lines are obtained. The line is assumed to have an initial exponential doping profile. An exact solution is obtained for the case of a constant charge being injected into the structure. An approximate solution is obtained for the case of a fixed voltage being applied at one end of the structure.     

Assessment of moisture content of fibres and fabrics by measurementof extinction cross-section in an open resonator

A new application of a large, computer-controlled open resonator is described. Measurement of the extinction cross-sections of samples of wet materials are recorded very quickly and continuously throughout the drying period. The measurements may be taken throughout the interval 8-12 GHz and provide a complete record of the drying process