Analysis of arbitrarily shaped multiple-dielectric posts in rectangular waveguide by method of lines

The equivalent network of arbitrarily shaped multiple-dielectric posts in a rectangular waveguide is analysed by the method of lines and the equivalent parameters of three cylindrical dielectric posts in a rectangular waveguide are calculated as an example.<>     

On the realizability of the impedance matrix for lossy dielectricposts in a rectangular waveguide

The equivalent T-network for some lossy dielectric posts in a rectangular waveguide is found to have a negative resistance in the parallel arm although the realizability conditions for the impedance matrix are strictly satisfied. Furthermore, the reactive part of the same impedance is found to be a monotonically decreasing function of frequency. These difficulties are overcome in the case of symmetrical post structures by using lattice networks. A simplified lattice network of lumped elements is developed to approximately realize the impedance matrix for resonant lossy post structures in the bandwidth     

Dielectric slab-loaded resonant cavity for applications requiringenhanced field uniformity

This paper introduces and analyzes a rectangular resonant structure that provides an alternative to the multimode resonant cavity in applications requiring enhanced field uniformity. The resonant cavity contains four dielectric loading slabs placed along the cavity walls. Its first resonant mode is related to the uniform field distribution supported in a rectangular TEM waveguide. The electromagnetic fields within the cavity are described using a closed-form approach, with approximations taken to account for the presence of two of the loading slabs. Application of the boundary conditions leads to an eigenvalue formulation, which is used to determine resonant frequencies and electromagnetic field distributions within the cavity. Measurements of both resonant frequencies and electric field magnitudes confirm the analysis. This work provides the basis for future analyses and implementation of slab-loaded cavities in both scientific and industrial settings     

Equivalent circuit formulation for an array of phased waveguide apertures

An expression for the radiation admittance of an infinite planar array of rectangular waveguide apertures is formulated and a technique for finding the complete equivalent circuit of the waveguide to space junction is given. The formulation includes multiple layers of dielectric above the array ground plane and waveguide elements which are center loaded with dielectric. Experimental verification of the radiation admittance formulation and the equivalent circuit concepts is given.     

Multiple Dielectric Posts in a Rectangular Waveguide

This paper presents a complete analysis for a system of Iinear, homogeneous, and isotropic dielectric posts in a rectangular waveguide. These posts are assumed uniform along the narrow side of the waveguide, but are otherwise of arbitrary cross section and thickness. The scattering and impedance matrices describing the effect of the posts on the dominant waveguide mode are derived. The latter is then realized as a two-port T-network. A moment procedure is devised and applied to a set of test problems with a wide variety of post configurations to compute the scattering parameters and equivalent network elements. The accuracy and convergence aspects of the numerical solution are also investigated. The branch and network resonances are determined for some post configurations.     

A simple method for accurate loss tangent measurement ofdielectrics using a microwave resonant cavity

A simple yet rigorous method has been developed to enable the loss tangent of dielectrics, having a known relative permittivity, to be accurately measured using a waveguide resonant cavity. The novel method eliminates the need for any physical measurement, either on the cavity or dielectric sample under test. The only electrical parameters that need to be measured are resonant frequencies and Q-factors of a reference cavity and those of the same cavity loaded with the dielectric sample. One of the advantages of the new technique is that dielectrics, of arbitrary shape, can be characterized at very high microwave frequencies. The new method has been verified through measurement over X-band     

Modeling of cylindrical dielectric resonators in rectangularwaveguides and cavities

The mode matching method is used to accurately model a generalized cylindrical dielectric resonator structure in a rectangular waveguide or cavity. The field distributions of different modes in cavities are given. The resonant frequencies of the cavities are calculated and compared to the measured data, showing very good agreement. The resonator structure can be a dielectric disk resonator, a ring resonator, a dielectric resonator with support, etc. This structure can be used in filter design as the basic element, providing very good mechanical stability. The slot coupling between cavities is also analyzed, showing some interesting results     

Resonant Frequencies of Rectangular Dlekctric Resonators

The resonant frequencies of isolated dielectric resonators of rectangular shape are calculated using the dielectric waveguide model. The waveguide treatment of the rectangular dielectric rod is solved using the approximate semianalytical techniques of Marcatili, Knox, and Toulios. The accuracy with measured frequencies appear satisfactory with the former approach.     

Analysis and experiment of substrate integrated waveguide cavity of four sidewalls of cylinders and solid top and bottom walls

Given in this paper are the equivalence formulas to convert the substrate integrated rectangular waveguide (SIW) resonant cavity of cylinder sidewalls (and solid top- and bottom-walls) to its equivalent rectangular wavguide cavity of solid sidewalls. The equivalence is analytical, therefore it should be excellent as long as the radius of the cylinders and their separation are small in terms of wavelength. Two prototypes are fabricated to demonstrate the validity of the equivalence formula. Excellent agreement of the measured and analytical resonant frequencies of TE₁₀₁ mode has been observed in the substrate integrated rectangular waveguide resonant cavity, indicating the accuracy of the proposed equivalence theory. Such equivalences are convenient for the design of small waveguides, of millimeter wave, in a multilayer circuit structure, such as the LTCC.     

Discontinuities in a Rectangular Waveguide Partially Filled with Dielectric

The modal spectrum for a rectangular waveguide with a dielectric slab at the bottom of the guide is obtained following the Characteristic Green's Function method developed by Marcuvitz. Then a four-terminal network is found as equivalent to the junction of the partially filled waveguide and an empty rectangular waveguide. An integral equation is written for the electric field at the plane of the junction and variational expressions are derived for the parameters of the four-terminal network connecting the transmission line equivalent to the partially filled waveguide to the transmission line equivalent to the empty guide. A reasonable guess for the electric field at the discontinuity gives approximate values for the parameters of the four-terminal network. These values agree with experiment. The parameters of the network are plotted vs frequency and thickness of the slab.     

Dielectric property measurement using a resonant nonradiative dielectric waveguide structure

This letter describes a new dielectric characterization technique, based on the resonant nonradiative waveguide structure described by Yoneyama and Nishida , for permittivity measurements at microwave and mm-wave frequencies. The measurement system is modeled as a resonator comprised of two parallel conducting plates with a rectangular dielectric slab sandwiched in-between. Resonant frequencies of the longitudinal section electric (LSE) modes and the unloaded Q of the cavity are used to determine the permittivity of the dielectric and its loss tangent, respectively. The technique is shown to be accurate for measuring the dielectric properties of a wide array of polymer and oxide materials. For materials with small dielectric loss tangents, an accuracy of better than /spl plusmn/0.4% is attained in the measurement of the relative dielectric constant of the material.     

Rectangular dielectric resonator antenna

An antenna which consists of a resonant rectangular parallelepiped dielectric on top of a ground plane is described. Calculated radiation patterns and measured impedances are presented, and the effects of feed probe length variations are discussed.     

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     

Electric and Magnetic Coupling through Small Apertures in Shield Walls of Any Thickness

A method is presented for evaluating the coupling between two identical resonant cavities coupled by a small aperture in a plane common wall of arbitrary thickness. The coupling is related to the frequencies of the symmetric and asymmetric modes of oscillation of the coupled cavity structure, and a variational technique is used to determine those frequencies. The method is applied to circular and rectangular apertures, and it is shown that the coupling is separable into electric and magnetic terms. The results enable theoretical solutions to be obtained for the electric and magnetic polarizabilities of circular and rectangular apertures in walls of zero thickness, and equivalent polarizabilities to be obtained when the wall thickness is nonzero. Curves of numerical values are given for circular and rectangular apertures. With zero wall thickness, the results obtained are the same as those of Bethe for a circular aperture and give good agreement with Cohn's experimental results for rectangular apertures.     

Coupling Holes Between Resonant Cavities or Wave-Guides Evaluated in Terms of Volume Ratios

A hole in a common wall is used to provide coupling between two resonant cavities (k=coefficient of coupling) or between two waveguides (x or b=normalized reactance or susceptance) or between cavity and waveguide (p=loading power factor of cavity). Referring to either side of a thin common wall, the field intensity in the center of a small hole is 1/2 what it would have been at that location on the wall. Between two equal regions, the coupling (k, x or b) by magnetic or electric field is expressed as 1/4 the ratio of the effective volume of the hole over the effective volume of each region, by duality (Booker's principle), the effective volume (related to the polarizability) of an aperture in a thin wall is identified with that of an analogous thin body in a uniform field. For a resonant cavity loaded by coupling to a waveguide, the loading power factor is p=kx; this theorem is proved by reference to an equivalent network. Various cases of coupling by two-dimensional and three-dimensional fields are formulated in terms of area or volume ratios, especially between pillbox resonators (rectangular, circular, or coaxial-circular) and between rectangular waveguides with common side walls or top and bottom walls. The effective area or volume of a small hole in a thin conducting wall is given for various symmetrical shapes, in a magnetic or electric field.     

Dual mode coupling by square corner cut in resonators and filters

A method for realization of dual-mode coupling in rectangular waveguide cavities is described and analyzed. The method completely replaces the coupling screw, and therefore can be used to eliminate the need for tuning in dual-mode waveguide cavity filters. It also offers a wide range of coupling values and can achieve higher power-handling capability than coupling screws. Mode matching is used to calculate the mode chart of the infinitely long square corner cut rectangular waveguide (SCCRW), the field distributions of each mode, and the resonant frequencies of the cavity. An evanescent mode rectangular waveguide is used to provide dual-mode couplings between adjacent cavities. The junction discontinuity between the SCCRW and the rectangular waveguide is modeled by a double mode-matching method, yielding modal scattering parameters of the junction. A four-pole dual-mode elliptic-function rectangular waveguide cavity filter using the coupling method was constructed. The experimental filter results showed excellent agreement with theory     

Three-dimensional finite-element method for solving electromagnetic problems

A 3-dimensional numerical method of determining the vector fields within a closed lossless electromagnetic system is described. The method is used to find the dominant-mode resonant frequencies for two cases of a rectangular cavity partially loaded with dielectric.     

Resonant Frequency and Q of an Open-Ended Rectangular Cavity

A field analysis of the TE /sub 10m/ resonant mode in an open-ended rectangular cavity is presented. The cavity geometry consists of rectangular waveguide with thick H-plane bifurcations for the terminations at each end. The bifurcation problem is solved by the method of modal analysis and a resonance criterion is established. Expressions for the cavity fields are written and used to compute stored energy, power lost, and Q. Calculated values for resonant frequency and Q are given and compared with experimental data.     

The Filling Factor of Shielded Dielectric Resonators

The use of dielectric resonators at microwave frequencies usually requires a shield to prevent loss of energy by radiation, and a coupling network. The efficiency of a given circuit depends on the filling factor, which expresses the circuit ability to store most of the input energy in the resonator, and little in the coupling network and surrounding space. The resonator is sometimes excited by means of a coupling loop inside the shield, or with a propagating waveguide. In any case, some energy is stored outside the dielectric material. A calculation is presented for the internal and external stored energies, for the case of a rectangular dielectric resonator in a rectangular waveguide. Verification was performed by measuring the insertion loss of an acoustic delay line, which illustrates an interesting application of dielectric resonators.