Analysis of a microstrip crossover embedded in a multilayeredanisotropic and lossy media

The equivalent circuit and the scattering parameters of the orthogonal microstrip crossover discontinuity are determined by assuming that the conducting strips are embedded in a multilayered substrate which may contain both anisotropic dielectrics and materials with a nonnegligible conductivity. The equivalent circuit of the crossover is obtained in terms of the complex excess charge densities on the strips. These excess charge densities are computed by means of the Galerkin method in the spectral domain. Comparison is carried out with previously existing results for microstrip crossovers on lossless isotropic substrates and original results are presented for crossovers on anisotropic and lossy substrates     

Electromagnetic waves scattering by cylindrical dielectric structures: Application to microwave devices design

A method which allows us to analyze the electromagnetic scattering characteristics of multiple discontinuities in shielded dielectric waveguides is presented. There are not restrictions both geometry of the cross section and electrical parameters of the dielectrics which are assumed to be linear, inhomogeneous, isotropic and free from losses. Each discontinuity is analyzed combining a modal matching technique with a generalized telegraphist's equations formulation; in this way, we obtain its scattering matrix. By using the concept of the generalized scattering matrix of two discontinuities, the equivalent generalized scattering matrix (EGSM) of the cascaded set is calculated. Theoretical and experimental results were obtained for different dielectric structures such as dielectric posts, isolated and coupled, as well as dielectric waveguides with circular cross section connected by means of abrupt and gradual transitions. The experimental values for the scattering properties show a good agrement with the theoretical ones. This study has shown the possibility of using cylindrical dielectric structures to design microwave devices such as: resonators, power-dividers and filters.     

Microstrip resonators on anisotropic substrates

The spectral domain method is applied to study shielded microstrip resonators printed on anisotropic substrates. A Green's function that takes into account the dielectric anisotropy effects is derived through a fourth-order formulation. Galerkin's method is then applied to form the characteristic equation from which the resonant frequency of the microstrip resonator is numerically obtained. Results for a microstrip situated on an isotropic substrate are used to validate the theory     

Spectral-domain analysis of shielded microstrip lines on biaxiallyanisotropic substrates

The spectral-domain technique is extended to the study of shielded microstrip lines on biaxial substrates. The analysis simultaneously includes dielectric and magnetic anisotropy effects. A fourth-order formulation leads to the determination of the appropriate Green's function for the structure. The characteristic equation is formed through the application of the Galerkin method to the equations resulting from the boundary conditions on the strip. Numerical results calculated by this method for isotropic as well as dielectrically anisotropic substrates are compared with the existing data, and in both cases a very good agreement is observed. New data on the propagation constant of the shielded microstrip with different substrate permittivities and permeabilities are presented to illustrate the effects of the material parameters on the characteristics of the microstrip line     

Microstrip Dispersion Including Anisotropic Substrates

A perturbation-iteration solution based on potential theory is developed for determining the effective dielectric constant, characteristic impedance, and current-charge distribution on a microstrip transmission line with isotropic and anisotropic substrates. The numerical implementation of the theory is described and is suitable for use on a personal computer. Computed data for several common substrate materials are included.     

Film technology in microwave integrated circuits

A review of the material technology for microwave integrated circuits (MICs) is presented. The types of microwave circuit media that have been used are described and classified as a function of the amount of size reduction or integration which corresponds to the effective dielectric constant of the media. The materials used for substrates, conductors, dielectrics, and resistors are considered in terms of the requirements for microwave circuits. The fabrication of multilayered thin-film circuits and the various thin-film combinations that have been used in MICs are discussed. The various loss contributions for microstrip circuits produced by thin- and thick-film technology and substrate material are compared with each other as a function of frequency. It is concluded that microwave circuits operating at frequencies 2 GHz and above require thin-films on pure smooth substrates.     

Effect of the Dielectric Anisotropy on the Propagation Properties of Microstrip Tapers with Height Variations

This paper deals with the design and application of nonuniform microstrip transmission lines on anisotropic substrates. A rigorous analysis is based on the use of Hertz vector potentials, moment method and transmission line theory to determine the dispersion characteristics of single and coupled tapered microstrip lines for accurate performance prediction. Results are presented for the main parameters providing the necessary information to design several devices on tapered microstrip, with variation on the strip width and dielectric height, for (M)MIC and antennas applications. A good agreement was observed with the results available in the literature for tapered lines on isotropic substrates.     

Modal Analysis of Microstrip Antenna on Fiber Reinforced Anisotropic Substrates

In this communication, microstrip antenna on fiber reinforced anisotropic substrates has been considered in aerospace applications; however, the antenna's optical axis may not necessarily be colinear with any of the substrate's principal axes and that leads to a nondiagonal permittivity matrix (tensor). This work extends the studies of microstrip antenna on isotropic substrate and on uniaxial substrate to analyze antenna performance on fiber reinforced anisotropic substrates, where the permittivity matrix has five dielectric constants because of the substrate's fiber direction. The solution is based on modal analysis so that the wave immittance can be derived in a closed form. Analyses and experimental verification show that the antenna performance is strongly influenced not only by the permittivity along the principal axes but also by the fiber direction of the substrate.     

Analysis of printed-circuit antennas with chiral substrates withthe method of lines

In this paper, a new method is presented in order to illustrate how the method of lines can be generalized for the analysis of stratified guided wave structures filled with isotropic chiral dielectric substrates. The new proposed method derives the dyadic Green's function for stratified isotropic chiral dielectric layers from the wave equation in the spectral domain. The result leads to a clear equivalent circuit representation of the whole structure, which can be used to readily handle the hyperbolic nature of the Maxwell equations. The application demonstrates the validity of the method to the well-known example of a single microstrip patch antenna on a single grounded isotropic dielectric layer. The technique is subsequently applied to more complicated structures with multiple isotropic chiral layers and electric sources and/or metallizations in arbitrary interfaces     

Hybrid Mode Analysis of Microstrip Lines on Anisotropic Substrates

A rigorous hybrid mode analysis is applied to microstrip lines on anisotropic substrates to determine its high-frequency performance. The analysis is based on a general formulation of the problem of planar transmission lines on multilayered substrates with uniaxial anisotropy, of which the microstrip line is a special case. Exact solution is obtained using a functional equation technique which was previously developed and applied to microstrip and bilateral finlines. The results were used to check the validity of the concept of equivalent isotropic substrate, suggested by some authors to simplify the calculation of the parameters of these lines. Certain approximations are introduced to allow the efficient calculation of the characteristics of microstrips on anisotropic substrates at relatively high frequencies or for wide strips. Numerical results are given for some values of the parameters of microstrip lines on sapphire and include the regions of excitation of higher modes.     

Comparison between theoretical and measured microstrip gapparameters involving anisotropic substrates

In this paper, experimental results are presented for microstrip symmetrical-gap discontinuities. The experimental technique is based on the measurement of the resonant frequencies of several gap-coupled rectangular microstrip resonators. In particular, gap discontinuities on anisotropic dielectric and two-layer composite substrates have been investigated. Reasonably good agreement has been found in most cases between theoretical data [obtained by means of the excess charge technique in the spectral domain (EC-SDA)] and experimental data, even though the theoretical results have been obtained by using a quasi-static approach     

Micromachined W-band filters

Results are presented for high performance planar W-band filters based on silicon micromachining techniques common in microsensor fabrication. Two types of micromachined planar transmission lines are studied: microshield line and shielded membrane microstrip (SMM) line. In both of these structures, the conducting lines are suspended on thin dielectric membranes. These transmission lines are essentially “floating” in air, possess negligible levels of dielectric loss, and do not suffer from the parasitic effects of radiation and dispersion. A 90 GHz low pass filter and several 95 GHz bandpass filters are tested and display excellent performance which cannot be achieved with traditional substrate supported circuits in CPW or microstrip configurations. A full-wave finite-difference time-domain (FDTD) technique verifies the measured performance of the W-band circuits and provides a basis for comparison between the performances of membrane supported circuits and equivalent substrate supported circuits     

Full-wave analysis of circular microstrip resonators inmultilayered media containing uniaxial anisotropic dielectrics,magnetized ferrites, and chiral materials

In this paper, Galerkin's method in the Hankel transform domain is applied to the determination of the resonant frequencies, quality factors, and radiation patterns of circular microstrip patch resonators. The metallic patches are assumed to be embedded in a multilayered substrate, which may contain uniaxial anisotropic dielectrics, magnetized ferrites, and/or chiral materials. The numerical results obtained show that important errors can be made in the computation of the resonant frequencies of the resonators when substrate dielectric anisotropy, substrate magnetic anisotropy and/or substrate chirality are ignored. Also, it is shown that the resonant frequencies of circular microstrip resonators on magnetized ferrites can be tuned over a wide frequency range by varying the applied bias magnetic field. Finally, the computed results show that the resonance and radiation properties of a circular microstrip patch on a chiral material is very similar to those of a circular patch of the same size printed on a nonchiral material of lower permittivity     

Equivalent isotropic relative permittivity of microstrip on multilayer anisotropic substrate

A closed-form model to obtain the equivalent isotropic relative permittivity of the multilayer microstrip line on the anisotropic substrate for 0 w/h ≤ 10, anisotropic ratio 0.5 ≤ n ≤ 3 for both low and high permittivity substrates is reported. The model has accuracy 0.5% against the full-wave method. It computes effective relative permittivity and characteristic impedance of microstrip on composite anisotropic substrates with deviations 5.3% and 1.78%, respectively against the EM-software Empire. It is used to obtain dispersion in multilayer anisotropic substrate microstrip up to millimetre wave range with high accuracy against the results of HFSS.     

Resonant modes of circular microstrip patches over ground planeswith circular apertures in multilayered substrates containinganisotropic and ferrite materials

In this paper, the authors analyze how the resonant modes of circular microstrip patch resonators are affected by the presence of circular apertures in the ground plane located under the patches. A rigorous full-wave analysis in the Hankel transform domain (HTD) is carried out in order to obtain the resonant frequencies, quality factors, and radiation patterns of the circular microstrip patch resonators over ground planes with circular apertures. With the use of suitable Green's functions in the HTD, the analysis is performed for the case where the circular patches, as well as the ground planes containing the apertures are embedded in a multilayered substrate consisting of isotropic dielectrics, uniaxial anisotropic dielectrics, and/or magnetized ferrites. The numerical results obtained are compared with experimental results, and good agreement is found. The results show that the circular apertures significantly affect the resonant frequencies of circular microstrip patches     

Quasistatic characteristics of microstrip on arbitrary anisotropic substrates

An analytical approach is used to find the upper bounds of microstrip line capacitance which arbitrary anisotropic substrate. General expressions are obtained for the permittivity and the thickness of an equivalent isotropic substrate. The method is used to compute the upper and lower bounds parameters of microstrip on sapphire substrate.     

Formulation générale de la méthode spectrale pour l’étude de structures planaires multicouches à tenseurs de permittivité et de perméabilité diagonaux

The materials usually used in microwave integrated circuits are often assumed isotropic. However, in certain cases anisotropy is introduced unintentionally during the manufacturing process, or deliberately in order to obtain non reciprocal devices, radar absorbers, and so on., or serves to improve circuit performances. In several cases, neglecting the anisotropy of certain substrates induces errors in integrated-circuit design. Hence the characteristics of planar structures containing anisotropic layers must be accurately described in order to secure the circuit design and improve the CAD models. On the other hand, the measurement of dielectric or magnetic anisotropy of materials at microwaves frequencies is of great interest for several applications and as such the planar structures on anisotropic layers can be used in this domain. Several methods enable the propagation characteristics to be calculated for a large number of structures such as microstrip, coplanar waveguides, and slotlines. The spectral domain technique (SDT) is one of the fastest. For anisotropic substrates, the formulation of the spectral domain method can be very difficult and it depends on the form of the relative tensors z and t. The main difficulty in considering anisotropic layers is to obtain the Green matrix of the spectral domain technique. The aim of this paper is to extent the SDT for 'planar lines on anisotropic (electric and/or magnetic) substrates. A generalized formulation for all diagonal and t is presented and used to calculate the propagation parameters for several planar lines.     

Accurate CAD-Model Analysis of Multilayer Microstrip Line on Anisotropic Substrate

Computationally efficient equivalent isotropic relative permittivity of the multilayer microstrip line on the uniaxial anisotropic substrate for 0 < w/h ≤ 10, anisotropic ratio0.5 ≤ n ≤ 3.0. Model has accuracy 0.5% against the full-wave method. It computes effective relative permittivity and characteristic impedance of microstrip on composite anisotropic substrates with deviation 4.5% respectively against the EM- software HFSS. Dispersion in multilayer anisotropic substrate microstrip up to mm wave range with high accuracy against the results of HFSS. The proposed models could be incorporated in the computer aided design for development of the components on the uniaxial anisotropic substrates.     

A new low-loss high-k temperature-compensated dielectric for microwave applications

A new dielectric material has been developed with a temperature-stable dielectric constant of 38. The low loss exhibited at microwave frequencies, the excellent reproducibility, and the good mechanical properties of this dielectric make it an attractive substrate for microstrip circuits. The dielectric is also suitable for the resonant elements of dielectric filters and stabilizing cavities for hybrid solid-state sources.