Rigorous analysis of shielded cylindrical dielectric resonators bydyadic Green's functions

This paper presents a rigorous approach for the calculation of resonant frequencies of a metallic cavity loaded by a dielectric resonator. Tangential fields at the air-dielectric interface are derived from dyadic Green's functions and boundary conditions are applied. Dyadic Green's identity and the boundary element method are used to solve the numerical problem. In order to validate the method, resonant frequencies are calculated for a cylindrical cavity loaded with a dielectric cylinder and compared with available results in the literature. Then resonance is studied for dielectric cylinder in a rectangular cavity. In the case of multiple dielectric resonators in the cavity, the coupling coefficient is computed with an original method based on the use of symmetries     

Numerical study of axisymmetric dielectric resonators

In this paper, we present an effective approach to study the behavior of axisymmetric dielectric resonators. This approach is based on the finite-difference time-domain method and two accompanying techniques in order to increase the accuracy and decrease the computational cost. These two techniques are the fast-Fourier-transform approach and the Pade method. This method is used to obtain the resonant frequencies and quality factors for several resonators. Comparisons are made to show the utility of the method     

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.     

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.     

Analysis of a coaxial-to-waveguide adaptor including a discendedprobe and a tuning post

A field matching analysis of a coaxial-to-waveguide adaptor incorporating a disc-ended probe and a tuning post is presented. In this analysis, the tuning post is considered as a short-circuited second probe. A computer algorithm for calculating the input impedance of this structure is developed. This algorithm is used to investigate and improve the operation of a commercially available coaxial-to-waveguide adaptor     

Resonant frequency analysis of dielectric ring resonators

The mode-matching technique is applied to guided and continuous spectra to derive the resonant frequencies of the high-order azimuthal modes of dielectric ring resonators. The numerical results of this field theory analysis are in close agreement with the measurements in the X-band     

Numerical analysis of two-arm spiral antennas printed on afinite-size dielectric substrate

A two-arm spiral antenna (SA) printed on a dielectric substrate backed by a conducting plane is analyzed under the condition that the dielectric substrate has a finite side length of L. The analysis is performed using the finite-difference time-domain (FDTD) method. The computation space for the FDTD method is reduced to one-half of the full computation space by virtue of the antenna arm symmetry with respect to the feed point. The numerical evaluations for the radiation characteristics are briefly described, and the SA_∞ (the spiral antenna with a conducting plane of infinite extent) is analyzed. It is found that the input impedance remains constant with side length L⩾0.8 wavelength in this analysis model. It is also found that as L increases, the axial ratio improves with the gain remaining relatively constant (the gain variation is within 1 dB). The SA_finite (the spiral with a conducting plane having the same finite size as the dielectric substrate) is also analyzed. It is revealed that the effects of L on the axial ratio and gain are relatively large compared with those on the former SA_∞     

Precise computations of resonant frequencies and quality factorsfor dielectric resonators in MICs with tuning elements

In this paper, the highly accurate results of resonant frequencies, field distributions, and quality factors of the TE_01δ mode for the cylindrical shielded dielectric resonator (DR) in microwave integrated circuits (MIC's) with a practical tuning element, such as the metallic tuning screw and the dielectric tuning device, are presented. By using the newly developed FD-SIC method, numerical results can be calculated accurately and efficiently. The DR structures with tuning elements can be more easily modeled by the present approach than the other methods using approximate solutions or the mode-matching (MM) methods. Numerical results in the literature are compared to the present FD-SIC results for the DR without tuning elements and detailed discussions on these results are given. In addition, design curves are also presented for the DR with the metallic tuning screw and with the dielectric tuning device. These design curves are helpful for designing DR systems with tuning elements in MIC applications     

Tunable, temperature-compensated dielectric resonators and filters

A thermal and electromagnetic model of a tunable hybrid-mode dielectric double resonator is introduced and analyzed by the mode-matching technique. Results of the analysis show the temperature sensitivity of the structure as a function of the center frequency as well as the other resonator parameters. A simple optimization procedure which allows the design of the resonator to have both a wide tunability range and good thermal stability of the resonant frequency is described. A circuit model is presented for a tunable four-pole dual-mode filter. The model exhibits interesting dual passbands, separated by a very-high-attenuation stopband. Measured results obtained from an experimental four-pole dual-mode dielectric resonator filter designed using the tunable hybrid-mode resonators showed excellent tunability range (200 MHz at C-band) and good agreement with the circuit model     

FDTD analysis of dielectric resonators with curved surfaces

In this paper, the finite-difference time-domain (FDTD) method is applied to calculate the resonant frequency of dielectric resonators (DRs) with curved surface. The contour-path integral FDTD (CFDTD) is modified to deal with the curved surface of the dielectric body while the traditional rectangular cells are maintained. Results are compared with theoretical values and staircase approximation, and show that the present method is more accurate than the staircase approximation     

Comparative modal analysis of NRD parallelepiped dielectric resonators

The resonance modes of dielectric resonators having parallelepiped shape are extensively investigated in this work referring to the nonradiative dielectric (NRD) topology. Different numerical techniques, both rigorous and approximated (boundary elements, point matching, finite elements, transmission line approaches), are proposed and implemented to compute the relevant resonance spectrum as a function of the involved geometric and electromagnetic parameters. The theoretical results are discussed and compared also in connection with experimental investigations, carried out on suitable prototypes of NRD components. Qualitative and quantitative information is thus achieved to characterize with accuracy and efficiency the basic parameters (resonant frequencies, field configurations, etc.) involved in filter design and in other applications at microwaves and millimeter waves.     

Best approximation for design of natural resonance frequencies of microwave dielectric disc resonators

Une méthode nouvelle pour le calcul des fréquences de résonance des résonateurs diélectriques cylindriques est présentée. La condition de court-circuit magnétique imparfait appliquée successivement à toutes les parois augmente considérablement la précision. Les valeurs théoriques et expérimentales diffèrent au plus de 1%. We present a new method for efficient computation of the resonance frequencies of dielectric disc resonators. Successive applications of imperfect open-circuit boundary conditions to all walls greatly improve the accuracy for resonance frequencies. Theoretical values agree within 1% of experimental results.     

Electrodynamic analysis of irregularities based on a shielded dielectric waveguide

Several functional elements exhibiting filtering properties are calculated on the basis of a rigorous solution to the 3D problem of diffraction by a junction of shielded dielectric waveguides (SDWs). It is shown that the solution to the diffraction problem depends heavily on the SDW dispersion characteristics that contain two-value sections in the region of propagating waves and indicate the presence of backward waves in regular waveguides. It is demonstrated that parallelepiped dielectric waveguides placed in the interior of a shielded waveguide enhance the efficiency of small bandpass filters.     

Numerical analysis of GaAs MESFETs with p-buffer layer on semi-insulating substrate including deep traps

Numerical analysis of GaAs MESFETs with a p-buffer layer on the semi-insulating substrate is presented in which impurity compensation by traps is included. Using a p-buffer layer is shown to be effective in minimising the short-channel effects as in the case of using a substrate with high density of traps.<>     

分析非均匀填充圆柱介质谐振器的二阶精度FDTD公式

从积分形式的Maxwell方程出发，利用连续函数的Taylor级数展开，严格地给出了包含介质交界面的二阶精度时域有限差分(FDTD)公式，解决了以往FDTD法处理非均匀介质填充区域问题时只有一阶精度的问题。分析表明，为了获得二阶精度，除了需要引入适当等效介电常数外，还必须采用适当非均匀网格。该方法被用于轴对称圆柱介质谐振器的分析。计算结果与理论值吻合良好，计算精度比传统的FDTD方法提高了一个数量级以上。     

Fast numerical analysis of dielectric resonators with perturbed rotational symmetry

A fast finite difference frequency domain (FDFD) formulation for obtaining resonant frequencies of structures with perturbed rotational symmetry is described. The formulation combines a three-dimensional (3-D) eigenfunction function expansion algorithm with 3-D FDFD in the cylindrical coordinate system. Numerical tests have showed that the technique gives high accuracy results and significant CPU time reduction.     

Integration equation analysis on resonant frequencies and qualityfactors of rectangular dielectric resonators

In this paper, the resonance problem of rectangular dielectric resonators (DRs) is analyzed by using the spectral dyadic Green's function and volume integral-equation formulation. The rectangular dielectric body is replaced by a set of entire-domain polarized volume current basis, and Galerkin's moment method is used to solve the resonant frequency and quality factor of the rectangular DR. The effects of electrical and geometrical parameters on the resonance of the TE₁₁₁ mode of isolated DRs are also presented. Additionally, the case of a rectangular DR with a ground plane is also discussed. Results are found to be in good agreement with the published experimental data     

多层介质天线罩的数值分析

针对含有多层薄层介质的电大尺寸多尺度问题计算的难点,提出了多层薄层介质的等效阻抗边界条件,该边界条件计入了薄层介质引起的电磁场幅度和相位的变化,可简化含多层薄层介质电磁结构的计算,解决多层天线罩薄层介质引起的剖分奇异化问题,实现多层天线罩对于天线性能影响的数值研究。     

Extended spectral domain approach for analysis of lossy cylindrical dielectric resonators

The spectral domain approach is extended for evaluating both the resonant frequency and Q factor of a lossy cylindrical dielectric resonator operating in TE/sub 0/ modes, taking into account the effects of conducting enclosure and supporting substrate. On the basis of the equivalence principle, the circular electric currents are introduced to simulate the fields inside and outside the cylindrical dielectric sample, which separates the original problems into two auxiliary structures with radially homogeneous multilayered dielectrics. Using the spectral immittance method in conjunction with the point-matching method, the characteristic equations are derived. The present technique has no need to determine the time-consuming, complex higher-order modes. Some typical examples are computed. The numerical results agree well with experimental data available in the literature.<>     

Three-dimensional higher-order mode analysis of transition from waveguide to shielded dielectric image line

The transition from a rectangular waveguide to a shielded dielectric image line is analysed by means of a mode-matching technique. The analysis takes into account higher-order modes also beyond the cutoff frequency. The numerical results of this field-theory analysis are in good accordance with measurement, in contrast to the usual transmission-line theory approach.