V. Fouad Hanna

Analysis and design of slot-coupled directional couplers between double-sided substrate microstrip lines

The characteristics of a slot-coupled directional coupler between two microstrip lines coupled through a rectangular slot in the common ground plane are studied. First, conformal mapping techniques are used to obtain analytic closed-form expressions for the coupler even and odd mode impedances and propagation constants for any coupler configuration. Secondly, a full-wave analysis is performed using the spectral domain approach to determine the dispersion properties of the coupler parameters. Theoretical and experimental results for a 10 dB coupler at 10 GHz are presented.<<ETX>>

A new global time-domain electromagnetic simulator of microwave circuits including lumped elements based on finite-element method

This paper proposes an extension of the Finite Element Time Domain (FETD) method for the global electromagnetic (EM) analysis of complex inhomogeneous microwave distributed circuits, containing linear or non linear lumped elements. This technique combines Maxwells equations and circuit equations, using directly SPICE software. Results are given for a capacitor, a resistor as well as a Schottky diode.

Three dimensional finite element analysis of N-port waveguide junctions using edge-elements

The finite element method is formulated in such a way that the electromagnetic solution of an excited cavity formed from an N-port waveguide junction leads directly and naturally to circuit characteristics of this junction. The use of edge elements eliminates nonphysical solutions. The reliability of the solution is assured compared to a penalty method. Accuracy of the method is demonstrated through the presentation of results for a waveguide T-junction while its efficiency is proven through the presentation of results for a case study of a finline step discontinuity.<<ETX>>

Numerical simulation of a virtual matched load for the characterization of planar discontinuities

A mixed technique, based on the association of the integral equations solved by the method of moments to the theory of loaded scatterers, is shown to be useful for simulating planar discontinuities. The theory of loaded scatterers is used to include the effects of either localized or distributed loads through which the matching can be achieved. When using this technique for shielded discontinuities, the scattering parameters are obtained from the knowledge of only current or electric field maxima, and the errors associated with the accurate determination of the current or the electric field minimum evaluation encountered in other techniques are avoided.<<ETX>>

Equivalent circuit representation of lossy coplanar waveguides

The study of the dispersion properties of planar transmission lines including metallic losses with the generalized transverse resonance method is formalized in building an equivalent network of the cross-section which specifies the relationships between the tangential components of the fields on each side of the interfaces. Virtual sources represent the trial quantities chosen to describe the problem. With twoport type boundary conditions, the trial quantities are not easily defined from physical considerations, but the virtual sources obey to specific rules. This purpose is illustrated in studying the attenuation in lossy suspended coplanar transmission lines.RésuméĽétude de la dispersion des lignes planaires présentant des pertes ohmiques par la méthode de la résonance transverse généralisée, se formalise au moyen ďun circuit équivalent de la section droite qui rend compte des relations entre les champs tangentiels aux interfaces. Des sources virtuelles représentent les grandeurs ďessai retenues pour formuler le problème. Comme les conditions aux limites sont de type quadripôle, ces grandeurs ďessai ne peuvent se déduire de considérations physiques, comme dans le cas sans perte, mais les sources virtuelles obéissent à certaines règles. Cette démarche est illustrée par ľétude de ľatténuation de lignes coplanaires suspendues.

Inverse source characterization for electromagnetic near field reconstruction and interaction with the environment

Antennas are sources of electromagnetic radiation. The radiation pattern and gain can be routinely obtained by measurements and characterize efficiently the radiation of the source regardless of its actual complexity. However in some applications, one may need to analyze the source interaction with its close environment in the near field region instead of the far field one. In this paper, we partition the antenna geometry with overlapping smaller spheres than the minimum one. The field at a point in the near field is the superposition of the field radiated by the sub-sources or equivalent sources circumscribed by the small spheres. The inverse or synthesis problem is to find these equivalent sources given the radiation pattern or its spherical harmonics spectrum. The radiated fields of the equivalent sources are expanded in terms of spherical harmonics which is locally associated with their minimum spheres

Packaging and interconnection mutual coupling effects in planar structures and discontinuities

An integral equation technique that is solved by the method of moments is used to analyze parasitic coupling in general shielded planar structures. The coupling between a planar component and its enclosure and the coupling between planar component themselves are studied. The first effect is illustrated by the calculated values of the effective permittivity of uniform planar lines and the S-parameters for a suspended stripline stub discontinuity for different enclosure geometries. The mutual coupling between two small spaced microstrip stubs is also discussed. Comparison with other numerical results as well as with published experimental ones has verified the accuracy and the numerical efficiency of the present approach.<<ETX>>

A New Approach of the Source Method for Characterization of Planar Structures

An analysis of planar circuits using the source method is presented. The definition of the input impedance seen from the source shows the arbitrary nature of the current source. An homographical relation, which relates the computed values to the true values of the input impedance, is demonstrated. Coupling two-port networks are introduced between the source and the access line of the circuit. The scattering parameters of a microstrip step discontinuity are given as an example.

Theoretical and experimental investigation of some general suspended stripline discontinuities

An integral equations technique associated with a 2-D moment method is used to characterize some general suspended stripline discontinuities, i.e., a stub, a meander, a bend, and a bent-stub, for which two components for strip surface current are taken into consideration. A numerical simulation of a matched load at terminations of the discontinuities is achieved and is used for a precise determination of scattering matrix parameters for these discontinuities. Good agreement is achieved between numerical results and experimental ones that are obtained using the de-embedding calibration technique. The effect of parasitic waveguide modes is discussed.<<ETX>>

Combining neural networks and iir filters for circuit microwave design and optimization in the time domain

A method combining Infinite Impulse Response (IIR) filters and Neural Networks (NN) is proposed for modeling and optimizing Electromagnetic (EM) structures. This method is based on the characterization of the time response as a transfer function using a digital filter. The use of the neural network allows then the modeling of the geometric variation of the studied structure. The validity of our proposed technique is demonstrated on a step in width and a microstrip filter.