Thorsten Tischler

Modeling dispersion and radiation characteristics of conductor-backed CPW with finite ground width

Dispersion and radiation properties of the conductor-backed coplanar waveguide (CPW) with finite ground planes are analyzed and modeled. A frequency-domain finite-difference method using the perfectly matched layer absorbing boundary condition is used as reference. Based on these results, a closed-form description is derived and implemented into an existing quasi-static CPW model. This leads to a comprehensive and efficient CPW description accounting for all relevant effects from conductor loss to high-frequency dispersion. Additionally, design rules to avoid parasitic radiation effects are given.

The perfectly matched layer as lateral boundary in finite-difference transmission-line analysis

Using PML as a lateral boundary in waveguide analysis introduces artificial modes and other unexpected effects. The paper presents results of a finite-difference frequency-domain approach, verified for a leaky-wave antenna, and provides analytical considerations supporting these findings. Particularly, the problem of detecting the desired modes out of the mode spectrum is addressed.

Dispersion and radiation characteristics of conductor-backed CPW with finite ground width

Dispersion and radiation properties of the conductor-backed CPW are studied. A frequency-domain finite-difference method using the PML absorbing boundary condition is used. The different types of higher-order modes are identified and design rules to avoid parasitic effects are given. Radiation is found to be considerably smaller than for infinite ground width.

Via arrays for grounding in multilayer packaging - frequency limits and design rules

Many packaging concepts use via arrays for grounding and to eliminate parasitic modes. Such arrays represent periodic structures and change their behavior beyond a certain frequency. Proper design of via geometry and pitch is necessary. For this purpose, electromagnetic simulation data and an equivalent circuit model are presented.

Broadband characterization of a microwave probe for picosecond electrical pulse measurements

The time-domain characterization of high-frequency devices with coaxial connectors requires the transfer of picosecond electrical pulses between coplanar and coaxial lines. Microwave probes are often used for this purpose. In this paper, the propagation of ultrashort electrical pulses over a microwave probe attached to a coplanar waveguide is experimentally studied by time-domain electro-optic sampling. From the experimental data, the attenuation and dispersion constants of the probe are determined up to 400 GHz. Moreover, the complex reflection and transmission coefficients of the junction between the microwave probe and the coplanar waveguide are extracted. Simple approximations are given for these quantities. These data can be used to predict the amplitude and shape of ultrashort electrical pulses after propagation over the microwave probe for arbitrary input pulses in the considered frequency range.

Accuracy limitations of perfectly matched layers in 3D finite-difference frequency-domain method

The perfectly matched layer (PML) boundary condition is employed in conjunction with the 3D finite-difference frequency-domain method (FDFD) for S parameter calculation of microwave devices. We find a residual reflection error, which is related only to discretization at the PML interface. The paper presents a systematic investigation of this parasitic effect and its origin.

On the computation of eigen modes for lossy microwave transmission lines including perfectly matched layer boundary conditions

The design of microwave circuits requires detailed knowledge on the electromagnetic properties of the transmission lines used. This can be obtained by applying Maxwell’s equations to a longitudinally homogeneous waveguide structure, which results in an eigenvalue problem for the propagation constant. Special attention is paid to the so‐called perfectly matched layer boundary conditions (PML). Using the finite integration technique we get an algebraic formulation. The finite volume of the PML introduces additional modes that are not an intrinsic property of the waveguide. In the presence of losses or absorbing boundary conditions the matrix of the eigenvalue problem is complex. A method which avoids the computation of all eigenvalues is presented in an effort to find the few propagating modes one is interested in. This method is an extension of a solver presented by the authors in a previous paper which analyses the lossless case. Using mapping relations between the planes of eigenvalues and propagation co...

Simulation of Microwave and Semiconductor Laser Structures Including Absorbing Boundary Conditions

The transmission properties of microwave and optical structures can be described in terms of their scattering matrix using a three-dimensional boundary value problem for Maxwell’s equations. The computational domain is truncated by electric or magnetic walls, open structures are treated using the Perfectly Matched Layer (PML) Absorbing Boundary Condition. The boundary value problem is solved by a finite-volume scheme. This results in a two-step procedure: an eigenvalue problem for general complex matrices and the solution of a large-scale system of linear equations with indefinite symmetric complex matrices. The modes of smallest attenuation are located in a region bounded by two parabolas, and are found solving a sequence of eigenvalue problems of modified matrices. To reduce the execution times a coarse and a fine grid, and two levels of parallelization can be used. For the computation of the discrete grid equations, advanced preconditioning techniques are applied to reduce the dimension and the number of iterations solving the large-scale systems of linear algebraic equations. These matrix problems need to be solved repeatedly for different right-hand sides, but with the same coefficient matrix. The used block quasi-minimal residual algorithm is a block Krylov subspace iterative method that incorporates deflation to delete

Numerical Simulation for Lossy Microwave Transmission Lines Including PML

Finite-difference analysis of transmission lines including lossy materials and radiation effects leads to a complex eigenvalue problem. A method is presented which preserves sparseness and delivers only the small number of interesting modes out of the complete spectrum. The propagation constants are found solving a sequence of eigenvalue problems of modified matrices with the aid of the shift-andinvert mode of the Arnoldi method. In an additional step non physical Perfectly Matched Layer modes are eliminated.

Perfectly matched layers in transmission lines

The field distribution at the ports of the transmission line structure is computed by applying Maxwell’s equations to the structure and solving a sequence of eigenvalue problems of modified matrices. A new strategy is described which allows the application of the method, first developed for microwave structures, to optoelectronic devices.