Surface wave excitation from open microstrip discontinuities

Radiation properties of open microstrip discontinuities are investigated using a full-wave integral equation technique. Formulas are presented to characterize power loss from open microstrip discontinuities. The technique utilizes microstrip current distributions obtained with the method of moments. The formulas allow the separation of total loss into the individual contributions of space wave and surface wave radiation and indicate the direction in which surface wave power is propagating within the substrate. Patterns depicting the power propagating in the substrate have been computed and verified experimentally     

Finite element analysis of MMIC structures and electronic packagesusing absorbing boundary conditions

In this paper, a three-dimensional finite element method (FEM) is employed in conjunction with first and second-order absorbing boundary conditions (ABC's) to analyze waveguide discontinuities and to derive their scattering parameters. While the application of FEM for the analysis of MMIC structures is not new, to the best of the knowledge of the authors the technique for mesh truncation for microstrip lines using the first and higher-order ABC's, described in this paper, has not been reported elsewhere. The scattering parameters of a microstrip discontinuity are computed in two steps. As a first step, the field distribution of the fundamental mode in a uniform microstrip is obtained by exciting the uniform line with the quasi-static transverse electric field, letting it propagate, and then extracting the dominant mode pattern after the higher order modes have decayed. In step two, the discontinuity problem is solved by exciting the structure by using the fundamental mode obtained in step one. The scattering parameters based on the voltage definition are calculated by using the line integral of electric fields underneath the strip. Numerical solutions for several waveguide discontinuities and electronic packages are obtained and compared with the published data     

A new CAD model for the full-wave characterization of microstrip line and its discontinuities

This work presents a new mathematical model for characterization of the microstrip and its discontinuities by the dynamic approach based on the exact Green's function for a grounded dielectric slab and the ameliorated Galerkin method. Some improvements are brought to the theoretical model of Jackson and Pozar (1985, IEEE Trans. Microwave Theory & Techniques, 33, 1036–42), which is our starting point. The present model has given very good results for the characterization of the microstrip line and its discontinuities of open end and gap, compared with previous theoretical and experimental results.     

A planar-lumped model for coupled microstrip lines anddiscontinuities

A convenient model for analyzing coupled microstrip line discontinuities is presented. A planar-lumped model similar to the planar waveguide model for single microstrip lines is developed for coupled microstrip lines. Fields underneath the two strips and those fringing at the outer edge are modeled by two equivalent planar waveguides. Electric and magnetic field coupling in the gap region is modeled by a lumped network. The lumped network parameters are evaluated such that [C] and [L] matrices for the model are identical with those for coupled lines. The model is verified by comparing coupler characteristics with those obtained by the conventional coupled line analysis. Just as the planar model of a single microstrip has been used for characterizing microstrip discontinuities, the planar-lumped model developed is used for coupled line discontinuities. Examples given include coupled microstrip sections with chamfered bends located at right angles to single microstrip lines, for which the results are in good agreement with experimental values     

Resonant techniques for establishing the equivalent circuits of small discontinuities in microstrip

The accurate measurement of small discontinuities in microstrip by conventional means is limited by the imperfections of the microstrip to coaxial transition. By using a resonant technique where such imperfections cause only 2nd-order errors, the equivalent circuit of microstrip discontinuities can be measured. To demonstrate the method, a 90° corner, with and without a chamfer, has been measured.     

Capacitance Parameters of Discontinuities in Microstriplines

Capacitance components of microstrip equivalent circuit discontinuities of gaps and the T junctions have heen calculated using the quasi-static formulation. Comparison of the calculated results with experimental measurements where available show good agreement. The range of data extends that data previously published, and new results on parallel gaps also are included.     

Computer-Aided Design of Microstrip Filters Considering Dispersion, Loss, and Discontinuity Effects

A computer-aided design procedure of microstrip filters involving junctions and discontinuities is investigated. The analysis of microstrip filters is described in detail considering disperion, loss, and the frequency dependent properties of the microstrip discontinuities. It is found that the described analysis procedure leads to an accurate fast numerical computation of the microstrip filter properties. The theoretical results for some filter structures are compared with measurements, and theory and experiment are found to correspond closely.     

A finite element cavity resonance method for waveguide andmicrostrip line discontinuity problems

This paper presents a novel finite element cavity resonance method for analyzing waveguide and microstrip discontinuities. The method originates from the classical nodal shift measurement technique for waveguide discontinuities, and is closely related to the transverse resonance technique (TRT). The method differs from the TRT in two important ways. First and foremost, the tedious search required in the TRT approach for the three sets of cavity lengths that satisfy the resonance condition at each of the specified frequencies of interest, is avoided in the present method. It is replaced, instead, with the problem of computing the resonant frequencies of the cavity for a number of different, systematically-chosen, longitudinal dimensions. The frequency behaviors of the S-parameters are reconstructed later for a wide band of frequencies from the sampled resonant frequency data by using an interpolation procedure described in the paper. Second, the finite element method (FEM) employing vector finite elements is used in conjunction with the numerically efficient Lanczos algorithm to compute the cavity resonant frequencies in an iterative manner. Several waveguide and microstrip line discontinuity problems have been analyzed by using this method. Numerical results are compared with available data     

Analysis of multilayer printed arrays by a modular approach basedon the generalized scattering matrix

In this paper, a modular technique is used to treat infinite multilayer printed arrays with apertures and patches of irregular shapes. Each array layer is characterized by a generalized scattering matrix (GSM) from which the overall GSM of the multilayer structure is computed. The excitation of each element is modeled as a transition from the microstrip line to an aperture in the ground plane. The GSM of this transition is computed using the reciprocity theorem and spectral domain moment method. Several arrays have been analyzed by the proposed technique and the numerical results are in good agreement with other theoretical and experimental data     

Effect of substrate dielectric anisotropy on the frequency behaviorof microstrip circuits

In this paper, we carry out a full-wave analysis of shielded two-port microstrip circuits, in which the metallizations are embedded in a multilayered substrate that may contain isotropic dielectrics and/or anisotropic dielectrics. The Galerkin's method in the spectral domain is applied for determining the current density on the metallizations of the circuits when their feeding lines are excited by means of delta-gap generators, and the matrix pencil technique is subsequently used for deembedding the scattering parameters from the computed current densities. Results are presented for the scattering parameters of some microstrip discontinuities and filters printed on both isotropic dielectric substrates and anisotropic dielectric substrates. These results show that when substrate dielectric anisotropy is ignored, errors arise when computing the scattering parameters of microstrip discontinuities and when predicting the operating frequency band of microstrip filters     

Analysis of a wide radiating slot in the ground plane of amicrostrip line

An analysis of a wide rectangular radiating slot excited by a microstrip line is described. Coupled integral equations are formulated to find the electric current distribution on the feed line and the electric field in the aperture. The solution is based on the method of moments and using the space domain Sommerfeld-type Green's function. The information about the input impedance or reflection coefficient is extracted from the electric current distribution on the microstrip line utilizing the matrix pencil technique. The theoretical analysis is described and data are presented and compared with other theoretical and experimental results     

A theoretical and experimental study of coplanar waveguide shuntstubs

A comprehensive theoretical and experimental study of straight and bend coplanar waveguide (CPW) shunt stubs is presented. In the theoretical analysis, the CPW is assumed to be inside a cavity, while, the experiments are performed on open structures. For the analysis of CPW discontinuities with air-bridges, a hybrid technique has been developed which has been validated through extensive theoretical and experimental comparisons. Throughout this study, the effect of the cavity resonances on the behavior of the stubs with and without air-bridges is investigated. In addition, the encountered radiation loss due to the discontinuities is evaluated experimentally     

Effects of Geometrical Discontinuities on Distributed Passive Intermodulation in Printed Lines

This paper presents the results of experimental study of passive intermodulation (PIM) generation in microstrip lines with U-shaped and meandered strips, impedance tapers, and strips with the profiled edges. It is shown that the geometrical discontinuities in printed circuits may have a noticeable impact on distributed PIM generation even when their effect is indiscernible in the linear regime measurements. A consistent interpretation of the observed phenomena has been proposed on the basis of the phase synchronism in the four-wave mixing process. The results of this study reveal new features of PIM production important for the design and characterization of low-PIM microstrip circuits.      

Analysis of microstrip discontinuities by FDTD method combined with SOC technique

In this paper, the application of the finite-difference time-domain (FDTD) algorithm combined with the short-open calibration SOC technique to three-dimensional microstrip discontinuity is presented. This SOC technique is directly accommodated in the FDTD algorithm. It is used to remove the unwanted parasitic errors brought by the approximation of the impressed voltage sources and the feed lines. The FDTD is formulated in such a way that the port voltages and currents are explicitly represented through relevant network matrices. This new method is also used to analyze finite periodic structures. The scattering parameters of the whole periodic structure can be approximately obtained through analyzing only one cell of it. The results for microstrip discontinuities and finite periodic structures are compared with the conventional FDTD method.     

Analyse de discontinuitiés rayonnantes sur ligne microruban au moyen d’équations intégrates

An integral equations technique solved by the moment method associated with the simple multiport model is used to analyse radiating open discontinuities in microwave circuits. Results obtained on a microstrip gap discontinuity are compared with those given by Hammerstad’s which are utilised in almost commercial cad software.     

The new method of time-domain analysis of a planar transmission line with discontinuity

In this paper, the new technique of time-domain analysis of discontinuities in a planar transmission line is presented. In the process of time-domain analysis, the analysis model of system and the concept of transfer function are employed and the frequency-domain method of lines and the technique of the fast Fourier transform are used. The results of time-domain data and frequency-domain characteristics for the shielded microstrip with step discontinuity are given and compared with the published results of other authors.     

Full-wave space-domain analysis of open microstrip discontinuitiesincluding the singular current-edge behavior

A full-wave space-domain analysis is presented for the high-frequency characterization of microstrip discontinuities. This approach solves the electric field integral equation (EFIE) for the surface current density on the microstrip using the method of moments. The current expansion functions incorporate the singular edge behavior of the surface current, yielding a very accurate current modeling. Special attention is devoted to the analytical treatment of the singular terms in the electric field Green's dyadic. The numerical results focus on the S-parameters of some simple microstrip discontinuities and the comparison with results obtained with other techniques and from measurements     

Analysis of a microstrip dipole antenna

Assuming a quasi-TEM mode of wave propagation and using a conformal transformation technique, accurate and simple analytic expressions for the characteristic wave resistance and the effective dielectric constant of the microstrip dipole antenna in the mixed dielectric medium have been derived. The theoretical values are in close agreement with the experimental results.     

Theoretical Investigation of the Input Impedance of Gap-Coupled Circular Microstrip Patch Antennas

In this paper, we have explored a simple theoretical input impedance computation technique for the two gap-coupled circular microstrip patch antennas by using circuit theory approach. The frequency characteristics of the input impedance of the two gap-coupled circular microstrip patch antennas with the gap-distance between the feed patch and parasitic patch is analyzed and simulated. The effect of feed location in the feed patch on the input impedance of proposed antenna is also studied. The theoretical results are compared with the simulated results as well as other reported literature. The simulation has been performed by using a method-of-moment based commercially available simulator IE3D.