P. Pribetich

Microwave performance prediction of a III–V semiconductor electrooptic waveguide modulator

The use of microwave modulations of optical waves allows one to obtain devices with very large bandwidths. Designers must solve two problems, one more specifically relevant to the optical field, the other in the microwave frequency range. The purpose of this paper is to focus the attention of optical device designers on microwave problems that occur when such modulators are made. To do so, we give some quantitative results relative to the microwave characteristics of such devices, when the hybrid nature of the microwave mode is taken into account.

Crosstalk Phenomenon in Coupled Microstrip Lines Laid on Semi-Conducting Substrates

Crosstalk phenomena and pulse propagation in coupled microstrip lines on insulating and semiconducting substrates are analysed. Propagation characteristics of these lines are obtained by Spectral Domain Analysis in order to avoid any error involved by the use of analytical model and T.E.M. approximation. Time domain results are calculated by a conventional fast Fourier transform. Effects of semiconducting layer, substrate thickness, lines spacing and length, loading impedances, on crosstalk and transfer are investigated.

Analysis of planar transmission lines and microshield lines with arbitrary metallization cross sections using finite elements methods

Propagation analysis is proposed to determine with much accuracy as possible, the dispersion characteristics for classical planar structures as well as for the new microstrip and coplanar membrane microshield lines both for microwave and millimeter wave ranges. These transmissions lines present an arbitrary cross section for the metallization of the strips and a finite value of the conductivity. We have developed two formulations of finite element methods in order to simulate such structures in the considered frequency range, showing the influence of lossy strips corner angles.<<ETX>>

Microwave characteristics of planar electrooptic modulator

An attempt is made to model traveling-wave optical modulators in the microwave frequency range by two methods: a desktop computer method based on the effective complex dielectric constant and a more rigorous method, i.e. the mode-matching technique. The aim is to quantify both bulk microwave and metallic losses and to determine the phase velocity in the microwave frequency range. This study takes into account the geometry of the cross section of the structure, the multilayered nature of the waveguide, and the hybrid nature of the mode. The two methods are compared for moderately lossy structures and shown to give quite similar results. However, when more realistic structures with highly doped multilayered substrates are considered, only the rigorous method can be used.<<ETX>>

Analysis of Quasicomplex Modes of Boxed Lossely Planar Lines for Millimeter Wave Applications by the Method of Lines

The communication proposed to show the existence of quasicomplex modes of boxed coplanar lines laid on a lossely dielectric substrate for millimeter wave applications, using the Method of Lines with nonequidistante discretization. These quasicomplex modes are defined by studying the behaviour of the two complex solutions of the propagation problem of the classical lossless boxed coplanar line versus the losses of dielectric substrate.

Analysis of quasi complex modes on lossy substrate boxed microstrip lines

Using the spectral domain approach improved by asymptotic expansions, it is shown by means of coupling integral values that the notion of quasi-complex modes can be introduced for lightly lossy substrates. The distribution of electric and magnetic fields in the cross section plane of a boxed microstrip line is shown as an example. Since for lossy structures all modes have a complex propagation constant, so the quasi-complex modes are particular modes with behavior similar to that of lossless structure complex modes.<<ETX>>

Full Wave Analysis of Superconducting Microstrip for MMIC Applications

We take into account the influence of the superconducting nature of the strip in order to study the behaviour of the superconducting microstrip line by means of two numerical methods. The first one is the Spectral Domain Approach modified by the surface impedance concept and the second one is the modified mode matching technique. This last one allows to simulate more accurately the presence of the superconducting strip without using surface impedance approximation.

Modelling of Superconducting Interconnections and Analysis of Crosstalk, Propagation Delay, and Pulse Distortion in High-Speed GaAs Logic Circuits

Crosstalk phenomena and pulse propagation in metallic and superconducting coupled microstrip lines on insulating and semiconducting substrates are analysed in this communication. Propagation characteristics of these lines are obtained by a numerical formulation which is an extension of the well known Spectral Domain Approach in order to simulate the nature of the strips and to avoid the errors involved by the use of analytical model or TEM approximation. Time domain results are determined by a conventional fast Fourier transform. Effects of the lossy nature and the thickness of the strips, semiconducting layer, substrate thickness, lines length, loading impedances, on crosstalk and transfer are investigated.

Analysis of microstrip resonator with a dielectric protective layer radiating into human body

A two-dimensional simulation of a microstrip resonator with a protective layer in contact with a multilayered lossy media is presented, which makes it possible to obtain the complex resonant frequency, i.e. the resonant frequency and the Q factor of the structure. The analysis is based on the two-dimensional spectral domain approach. This modeling approach constitutes a numerical simulation tool for determining the limits of validity of a simple transmission line model which can be implemented on a desktop computer. A comparison with experiment shows that the proposed method improves a previously presented one-dimensional modeling approach.<<ETX>>

An Extension of the Transmission Line Model for the Characterization of Microstrip-Microslot Applicator

In this paper, we present a new approach for the modelisation of the microstrip-microslot applicator used for biomedical applications. This device offers a lot of advantages for these applications but its modelisation is very complicated because of the various discontinuities on the microstrip lines and the coupling of the microslot with mediums of complex permittivity. Our usual models are improved by using the spectral domain approach in order to characterize the microstrip line with tuning septums, which constitutes the transmission line. The model used is based on the extension of the transmission line model of the radiating antennas. The validity of our approach is confirmed by comparison with experimental results.