Calculation of frequency and power characteristics of the composite metal-dielectric resonator using the method of partial regions

A new method for calculating the frequency and power characteristics of different modes of a microwave metal-dielectric resonator has been proposed. The results of measurements of experimental specimens are presented that are in good agreement with calculation results. The relationships of the frequency and power characteristics of a resonator as a function of its geometrical and electrophysical parameters were obtained by using the method of partial regions. A high sensitivity of the main mode resonant frequency to the thickness of air inhomogeneity was detected. In this case the introduction of inhomogeneity increases the resonator Q-factor. Thus, the proposed design can be used as a high-Q tunable resonator.     

Implementation of higher order forced oscillations mode in shielded dielectric resonators by using slotline

The electromagnetic characteristics of the shielded hemisphere dielectric resonator in 8-mm waveband were investigated experimentally. The utilization of a slotline for the excitation of whispering gallery modes in such resonator was suggested. It has been defined that the suggested excitation technique is efficient. It provides an opportunity to excite the high Q-factor higher order modes in shielded dielectric resonator without additional energy losses. It has been proved experimentally that the unloaded Q factor achieved in the resonator under investigation may exceed the threshold values, which are limited by the dissipative losses in the dielectric resonator material, due to the shift of the resonance field in the air gap between the metal and the dielectric resonator elements. It was demonstrated that the symmetry breakdown of the investigated resonator leads to a significant deterioration of its electromagnetic characteristics.     

电磁开腔测量双层介质复介电常数

本文提出了一种利用电磁开腔在微波和毫米波频段测量双层介质复介电常数的新技术。在８ｍｍ频段，利用一套电磁开腔自动测量系统对几种双层介质材料进行了具体测量。最后，对测量误差进行了理论分析，并给出了计算实例。     

新型电单负材料结构在天线互耦抑制中的应用

单负材料所具有的电磁禁带特性可应用于阵列天线中降低天线单元间的互耦.文中研究设计了一种电单负材料结构单元ENG-APSL, 采用等效电路和波导传输法分析了ENG-APSL的电磁特性, 并提取等效参数.然后, 将基于ENG-APSL单元构成的隔离器用于抑制微带阵列单元间的互耦.研究表明, 天线阵列单元间距为0.37λ₀(λ₀为天线工作频率波长)条件下, 加载隔离器后天线阵列单元的E面耦合度降低了21 dB, 并且在工作频率(5.1 GHz)附近隔离度大于25 dB的带宽达到5.1%.同时, 该隔离器具有结构简单、尺寸小的突出优势.     

New method for complex permittivity measurement of dielectric materials

A novel technique for the measurement of dielectric properties of a homogeneous isotropic material is described. An accuracy better than 1% can be obtained on the permittivity and loss tangent values. The structure used is a cylindrical metallic cavity, carrying at its centre the circular cylindrical dielectric sample. The complex permittivity is deduced from the comparison between the experimental and the computed electromagnetic characteristics (frequencies, quality factors) of the resonant TE01? mode of the dielectric resonator.     

电磁开腔测量多层介质样品复介电常数

本文提出了一种在毫米波和亚毫米波微段利用电磁开腔测量多层介质样品复介电常数的新方法。在ｋａ波段利用特制的开腔装置建立了一套电磁开腔电介质参数测量系统，并对一些多层介质样品进行了实际测量。测量结果与标称值十分吻合。     

Simple method for investigating electromagnetic properties of high-Tc superconductors at two-millimeter wavelengths

A method for investigating the electromagnetic properties of high-T_c superconductors (HTS) in a 2-mm wavelength band has been proposed. The method is based on the use of a cylindrical tube open dielectric resonator (ODR) loaded with a HTS sample. The Josephson harmonic generation at microwave frequencies can be investigated by means of the method. A small cross section of the ODR makes it possible to investigate surface variations of HTS sample electromagnetic properties and their temperature dependencies.     

Study of a combined millimeter-wave resonator

We present a theoretical investigation and measurements of a multielement open resonator composed of corrugated waveguides and plane semitransparent reflectors. A periodic-transmission-line model is used to analyze the transverse mode structure and the diffraction Q-factor of the proposed resonator. The setup containing the resonator (equipped with Bragg reflectors), mode converters, and an elliptical mirror is employed for measurements in Ka-band. Two- and three-waveguide-section resonators have been studied. The proposed resonators demonstrate good mode selectivity that permits one to utilize them in high-power millimeter-wave sources     

一种新颖的双陷波超宽带天线设计

针对超宽带系统易受窄带信号干扰的问题,设计了一种新颖的基于金属开口谐振环结构的双陷波平面超宽带天线。通过在天线的辐射贴片上加载U形槽和在接地板上引入寄生条带的方法实现了双陷波特性。利用仿真软件研究了U形槽和寄生条带的物理尺寸对陷波特性的影响,并对所设计的超宽带天线进行了制作和测量。仿真和测试结果表明,天线在超宽带系统3.1～10.6GHz工作频段内的电压驻波比小于2,在WiMAX和WLAN频率范围具有良好的陷波特性,有效地抑制了超宽带通信系统与窄带通信系统之间潜在的干扰。     

Remote identification of liquids in a dielectric container using millimeter waves. 1. Principal possibility

Thepossibility of applying short-range radiolocation in millimeter wave range for problem of remote identification of flammable and hazardous liquids, enclosed in dielectric containers is demonstrated for the first time. Developed measurement setup allows indoor investigations; and the level of emitted power of utilized devices is insignificantly higher than background noise level, or, equivalently, thermal radiation. The described radiometric measurement setup enables discriminating liquids having different physical and chemical properties, in particular discriminate between water and gasoline containers. Applying additional illumination, which increases the contrast of the object under test, is one of one of the features of developed design. Various noise sources were investigated to be used as additional illumination. It was shown that in case of short-range radiolocation, energy-efficient fluorescent lamp is the most affordable choice of radiometric illumination. Such lamp not only ensures sufficient noise level in the operating frequency domain, but also has in-built modulation device that allows using modulation regime of the receiver and enables higher sensitivity.     

Evolution of electromagnetic field in resonator with nonlinear paramagnetic filling

The problem deals with the evolution of the electromagnetic field inside resonator with the paramagnetic filling is considered. The complex magnetic susceptibility obtained from the Bloch equations has been presented in a form of power series intensity of the electromagnetic field. The solution of evolution equations describing the time dependence of the electromagnetic field inside the resonator under the conditions of harmonical excitation is obtained.     

THz-Wave Spectroscopy Applied to the Detection of Illicit Drugs in Mail

A series of experiments in the field of THz-wave spectroscopy is described. The measurement of absorption spectra of solid samples, powders, and liquids is demonstrated using various optical setups. One of the sources we used is a widely tunable coherent THz-wave generator relying on an optical parametric process: nanosecond Q-switched Nd : YAG laser light scattering from the polariton mode of a MgO-doped LiNbO₃ crystal. For the measurement of the absorption of THz waves in liquids, a train of waves is allowed to oscillate inside a silicon prism. A liquid placed on a total internal reflection surface lowers the quality factor of the resonator, which allows determining the complex refraction index of the sample by frequency scanning. We have also developed a technique for THz chemical imaging, by introducing the component spatial pattern analysis. The spatial distribution of the chemicals, such as illicit drugs concealed in an envelope, is obtained from terahertz multispectral transillumination images and absorption spectra. To compensate for the low imaging speed, a prescreening step is proposed, by first detecting the presence of powders in the envelopes, which is achieved by measuring in real time the amount of scattering produced by the envelopes. Details and examples are provided.     

A treatment of the phase properties of GTEM to open-area test-sitecorrelation techniques

The gigahertz transverse electromagnetic (GTEM) cell is a very attractive environment for the measurement of radiated emissions from electrically small equipment under test (EUTs). However, the GTEM is only accepted by the relevant measurement standards as long as the measurements in a GTEM can be used to predict the field that a particular EUT would produce on an open-area test site (OATS). Techniques for predicting equivalent OATS radiated fields from measurements in a GTEM have been developed. The techniques include the assumption that the dipole moments, which represent the radiation of an EUT, are all in phase. We analyze the case where the EUT dipole moments are not in phase and propose a new upper limit for the predicted OATS radiated field. Our new limit is up to 5 dB greater than the maximum predicted by the existing techniques, but over most of the frequency range the difference with the existing technique is about 3 dB     

Comparison Method of Measurement Q of Microwave Resonators (Short Papers)

A method for the measurement of the quality factor of microwave resonators is given. It is based on the comparison of the transmitted power of the measured resonator with that of a reference resonator. The characteristics obtained by simultaneous display of the transmitted powers of the two resonators in Cartesian coordinates are analyzed. The relationship between the shape of the resulting curve and the parameters of the reference and measured resonators is discussed. The principal scheme of the X-band measuring microwave set and the measurement procedure are described. Some verification of the measurement results are presented. The method described is especially convenient for measuring small relative changes in the quality factor. It can be utilized for measuring the microwave loss tangent of materials by perturbation resonator methods.     

Slot line excitation of whispering gallery oscillations in shielded dielectric resonators

Electrodynamic characteristics of a half-disc shielded dielectric resonator operating in the 8-mm wavelength range have been investigated experimentally. A slot line was proposed for the excitation of whispering gallery modes in such resonator. It has been found out that the proposed excitation technique is effective and allows the high-Q oscillations of higher orders to be excited in a shielded dielectric resonator without additional energy losses. The partial shielding of the resonator in question was proposed for its spectrum rarefaction.     

Design optimization of a hyperbolic unstable-resonatorsemiconductor laser

A semiconductor laser with a hyperbolic unstable resonator has been investigated through numerical simulations. The laser has an integrated focusing grating outcoupler. The complete device, including the resonator, outcoupler, and free-space propagation, has been modeled. Propagation in the resonator and the outcoupler grating has been modeled using a beam-propagation method that accounts for anti-guiding and thermal effects. The work has been aimed at optimizing the resonator layout for suppressed filamentation and wavefront distortion, i.e., to design a laser that produces an injection-independent focused spot. We show that small changes in the resonator layout can have a large effect on the laser performance and characteristics of the focused spot. We conclude that thermal effects, rather than anti-guiding effects, limit the performance of the device     

Method of Synthesizing Nonuniform Waveguides

A method is proposed for the synthesis of continuous nonuniform waveguides with rectangular cross section so that they show desired electromagnetic properties for discrete frequencies when excited by the TE/sub 10/ mode. Starting from a uniform structure with known properties, the shape of the nonuniform waveguide is attained step by step by small systematic deformations. To show the feasibility of the method proposed, the mathematical formalism and numerical results are presented for reactive one-ports and filters with simple properties. In these cases, the problem is reduced to the solution of an equivalent resonator problem, i.e., a nonuniform waveguide resonator is developed for which a certain set of resonance modes occur at desired frequencies.     

电磁开腔测量各向异性媒质复介电常数

本文利用微扰原理和复数源点法,对电磁开腔测量单轴各向异性媒质复介电常数进行了理论研究,并且定量地分析了在测量中由于媒质的各向异性引起的双折射现象。最后利用一套八毫米电磁开腔自动测量系统对几种石英晶体样品进行了实际测量。     

The impact of conditions and techniques of excitation of a half-disk dielectric resonator on characteristics of “whispering gallery” oscillations

The paper is devoted to experimental investigation of the impact of various conditions and techniques of excitation (by a local source and by a source with distributed parameters) of the “whispering-gallery-mode” oscillation in half-disk dielectric resonators on the characteristics of the resonator forced oscillation. The work discloses peculiarities of electrodynamic characteristics of the whispering-gallery oscillations from the viewpoint of distribution of their electromagnetic fields in a half-disk dielectric resonator.