Commercial Field Solver Research Articles

Uncertainty Quantification of Waveguide Dispersion Using Sparse Grid Stochastic Testing

To quantify waveguide dispersion uncertainty, we propose a stochastic analysis technique based on the polynomial chaos method, where Smolyak sparse grids are used as sample spaces for the recently developed nonintrusive stochastic testing (ST) technique. This strategy allows for a smaller set of candidate collocation nodes in the ST algorithm compared with the computationally expensive tensor grid approach. The method is tailored to the analysis of waveguide structures with a statistically spatially varying dielectric-property profile, which is then captured by a discrete set of uncorrelated random variables by means of Karhunen–Loeve transforms. In this way, the propagation properties of realistic stochastic waveguides can be predicted, which is of major importance in the electronic design process. The presented method, which is constructed around a second-order full-wave deterministic finite element solver, is illustrated through the uncertainty quantification of two waveguide dispersion problems and is validated using commercial electromagnetic field solvers and the Monte Carlo method.

Full Custom MEMS Design: 2.5D Fabrication-Process Simulation for 3D Field-Solver-Based Circuit Extraction

Due to the lack of sophisticated component libraries for microelectromechanical systems (MEMS), highly optimized MEMS sensors are currently designed using a polygon-driven design flow. The advantage of this design flow is its accurate mechanical simulation, but it lacks a method for an efficient and accurate electrostatic analysis of parasitic effects of MEMS. In order to close this gap in the polygon-driven design flow, we present a customized electrostatic analysis flow for such MEMS devices. Our flow features a 2.5D fabrication-process simulation, which simulates the three typical MEMS fabrication steps (namely deposition of materials including topography, deep reactive-ion etching, and the release etch by vapor-phase etching) very fast and on an acceptable abstraction level. Our new 2.5D fabrication-process simulation can be combined with commercial field-solvers such as they are commonly used in the design of integrated circuits. The new process simulation enables a faster but nevertheless satisfactory analysis of the electrostatic parasitic effects, and hence simplifies the electrical optimization of MEMS.

Accurate Modeling of Conductor Rough Surfaces in Waveguide Devices

To address the effects of surface roughness on wave propagation in the microwave and millimeter-wave bands, this paper studies electromagnetic wave propagation and focuses on the propagation loss within an inner environment featuring surface roughness of the metallic waveguide structures. The conductivity gradient model is first developed to treat surface roughness with inhomogeneous conductivity, and then the concept of a frequency-dependent effective conductivity is introduced to model the effects of surface roughness in waveguide structures. With the effective conductivity used in the commercial 3D field solver, High Frequency Structure Simulator (HFSS™), a surface impedance boundary condition strategy is applied on ideally smooth surfaces to model the actual behavior of rough metallic waveguide surfaces. Finally, the propagation performance is predicted by comparing the effects of surface roughness in metallic waveguide structures and the results from the models with ideally smooth surfaces, using rectangular waveguide, cylindrical resonator and coupling cavity filters models. Overall, this effective conductive concept can be applied using various commercial field solvers to handle surface roughness effects accurately and efficiently in any work involving conducting microwave structures.

Synthesis of high speed channels from shorter elements

We demonstrate a simple process to build complex channel models described by S-parameter models from simpler elements using a free, open source tool. The concept of cascading S-parameter models is discussed and the significance of using a free tool to implement this concept is explained. A sample channel involving several types of interconnects from multiple commercial field solver tools is used to show the power of this method. Further, this process is examined for artifacts by performing several consistency checks. A library consisting of building blocks of channels could be constructed to synthesize simple to complex channel models to explore signal integrity performance.

Conduction Mode Analysis and Impedance Extraction of Shielded Pair Transmission Lines

Conduction mode analysis is carried out for the shielded pair transmission structure (SPTS) by mode analysis using analytical electromagnetic methods. The analytical method takes into consideration both the skin effect and the proximity effect. A concise expression for calculation of the impedance parameter is derived directly from the mode analysis. The resultant impedance results are as accurate as those from the commercial field solver over a wide frequency range from 100 MHz to 100 GHz.

Inductive power transmission to millimeter-sized biomedical implants using printed spiral coils.

The operation frequency (f) has been a key parameter in optimizing wireless power transmission links for biomedical implants with millimeter (mm) dimensions. This paper studies the feasibility of using printed spiral coils (PSCs) for powering mm-sized implants with high power transmission efficiency (PTE) at different fps. Compared to wire-wound coils (WWCs), using a PSC in the implant side allows batch fabrication on rigid or flexible substrates, which can also be used as a platform for integrating implant components. For powering an implant with 1 mm diameter, located 10 mm inside the tissue, the geometries of transmitter (Tx) and receiver (Rx) PSCs were optimized at different fPs of 50 MHz, 200 MHz, and 500 MHz using a commercial field solver (HFSS). In simulations, PSC- and WWC-based links achieved maximum PTE of 0.13% and 3.3%, and delivered power of 65.7 μW and 720 μW under specific absorption rate (SAR) constraints at the optimal fp of 50 MHz and 100 MHz, respectively, suggesting that the performance of the PSC-based link is significantly inferior to that of the WWC-based link.

Optimal frequency for powering millimeter-sized biomedical implants inside an inductively-powered homecage.

This paper presents the optimal design and operation frequency (f) of an inductively-powered homecage for powering biomedical devices with millimeter (mm) dimensions, implanted inside the body of freely-behaving small animal subjects, for longitudinal behavioral neuroscience and electrophysiology experiments. In order to improve the power transmission efficiency (PTE) for powering mm-sized implants, the geometry of the multi-coil inductive links in the form of 3- and 4-coil links as well as fp need to be co-optimized. A simplified equation for the PTE of 3-coil inductive links for powering mm-sized implants has been derived, based on which the optimal geometries and fp of a 3-coil link have been found using a commercial field solver (HFSS). In simulations, the optimized 3-coil inductive link achieved a significant PTE of 2.56% at the optimal fp of 40 MHz for powering a 1 mm3 implant coil at the nominal height of 7 cm, thanks to the link and fp optimization as well as an intermediate coil in the receiver side with 18 mm diameter.

Exploiting antenna directivity in wireless NoC architectures

Wireless Network-on-Chip (WiNoC) is an emerging on-chip communication paradigm and a candidate solution for dealing with the scalability problems which affect current and next generation many-core architectures. In a WiNoC, the transceivers that allow the conversion between electrical and radio signals, account for a significant fraction of the total communication energy budget. In particular, the transmitting power for wireless communications is strongly affected by the orientation of the antennas. This paper studies the impact of antennas orientation on energy figures of a WiNoC architecture and performs a design space exploration for determining the optimal orientation of the antennas in such a way to minimize the communication energy consumption. Experiments have been carried out on state-of-the-art WiNoC topologies, on both synthetic and real traffic scenarios, and validated by means of a commercial field solver simulator. When the antennas are optimally oriented, up to 80% energy saving (as compared to the case in which antennas have all the same orientation) has been observed.

Aspects of and Insights Into the Rigorous Validation, Verification, and Testing Processes for a Commercial Electromagnetic Field Solver Package

This paper focuses on rigorous validation, verification, and testing methodologies applied to a commercial electromagnetic software package to ensure that as accurate as possible results are given dependent on the accuracy of the solution method, for instance, whether a full-wave or approximate numerical method is used. In this paper, the general availability of reliable benchmark results such as analytical solutions, measurements, results from other codes and other numerical methods, and general benchmarking activities will be presented. The cross-validation aspects, once the benchmark results are available, will be discussed with respect to amongst other sequential runs compared with parallel multcore/cluster runs or, with and without, GPU acceleration. Internal consistency checks (which are a required but not necessary condition when assessing the accuracy) such as power budget, mesh size convergence, or boundary condition error estimates are also covered. Special emphasis is put on the validation of the actual computational model that is used as input to simulations. This is necessary, for example, because incomplete representation of real geometry might ignore small details that are needed for the specific quantity that is analyzed. Also, uncertainties with regards to material parameters or transition impedances could lead to discrepancies between the computed results and reality that are not to be attributed to the electromagnetic solution as such, but rather the model generation.

Destructive impact of imperfect beam collimation in extraordinary optical transmission

We investigate the difference between analytic predictions, numerical simulations, and experiments measuring the transmission of energy through subwavelength, periodically arranged holes in a metal film. At normal incidence, theory predicts a sharp transmission minimum when the wavelength is equal to the periodicity, and sharp transmission maxima at one or more nearby wavelengths. In experiments, the sharpest maximum from the theory is not observed, while the others appear less sharp. In numerical simulations using commercial electromagnetic field solvers, we find that the sharpest maximum appears and approaches our predictions as the computational resources are increased. To determine possible origins of the destruction of the sharp maximum, we incorporate additional features in our model. Incorporating imperfect conductivity and imperfect periodicity in our model leaves the sharp maximum intact. Imperfect collimation, on the other hand, incorporated into the model causes the destruction of the sharp maximum as happens in experiments. We provide analytic support through an asymptotic calculation for both the existence of the sharp maximum and the destructive impact of imperfect collimation.

Analysis of slotted cylindrical ring resonators

Advances in mobile technology, due to the rapid growth of mobile wireless systems, coupled with stringent selectivity requirements, have led to the need for smaller and lighter high quality filters. The slotted cylindrical ring resonator is one resonator considered promising in the development of high quality compact filters for mobile communication systems due to its small size and medium to high Q-factor [1]. In this paper the Transmission Line Modeling method is used to determine the effects of using a high dielectric constant material on the size and coupling constant of the resonator. Modeling and simulations are done using Microstripes, a commercial TLM field solver from Flomerics. The paper shows that by placing a high dielectric constant material in the resonator gap the resonant size is decreased and the coupling improved.Keywords: Slotted cylindrical ring resonator, resonant frequency, electric coupling, magnetic coupling, Transmission line modeling

Optimization of Shielding Devices for Eddy-Currents Using Multiobjective Optimization Methods

Multiobjective optimization of shielding devices for eddy-currents is studied using several fundamentally different optimization methods. To solve the binary optimization problem of finding an optimal topology of the magnetic shunts a micro-genetic algorithm is used. In order to perform a parameter optimization of a given topology in terms of its placement, evolutionary strategies are applied. Finally, the multiobjective mixed binary-real optimization problem, with respect to both the topology and position of the magnetic shunts, is defined and solved using the micro-genetic algorithm. The conflicting objectives of minimizing Ohmic losses in the shielded body along with minimizing the volume of the shunts' magnetic material are taken into account in two different approaches. On the one hand all objectives are transformed into a single scalar value using the method of weighted functions; on the other hand Pareto optimal solutions are evaluated and assessed. To ensure the reliability of the obtained solutions, the evaluation of the objective functions is based on the 2-D finite-element method eddy-current analysis using both self developed and commercial field solvers.

Design and Optimization of Printed Spiral Coils for Efficient Transcutaneous Inductive Power Transmission

The next generation of implantable high-power neuroprosthetic devices such as visual prostheses and brain computer interfaces are going to be powered by transcutaneous inductive power links formed between a pair of printed spiral coils (PSC) that are batch-fabricated using micromachining technology. Optimizing the power efficiency of the wireless link is imperative to minimize the size of the external energy source, heating dissipation in the tissue, and interference with other devices. Previous design methodologies for coils made of 1-D filaments are not comprehensive and accurate enough to consider all geometrical aspects of PSCs with planar 3-D conductors as well as design constraints imposed by implantable device application and fabrication technology. We have outlined the theoretical foundation of optimal power transmission efficiency in an inductive link, and combined it with semi-empirical models to predict parasitic components in PSCs. We have used this foundation to devise an iterative PSC design methodology that starts with a set of realistic design constraints and ends with the optimal PSC pair geometries. We have executed this procedure on two design examples at 1 and 5 MHz achieving power transmission efficiencies of 41.2% and 85.8%, respectively, at 10-mm spacing. All results are verified with simulations using a commercial field solver (HFSS) as well as measurements using PSCs fabricated on printed circuit boards.

Extraction of LRGC Matrices for 8-Coupled Uniform Lossy Transmission Lines Using 2-Port VNA Measurements

The electrical parameters (8 × 8 LRGC matrices) of 8-coupled uniform lossy transmission lines were extracted from 40 S-parameter values measured by using 2-port VNA measurements, where all the ports other than 2 VNA ports were terminated by 50 ohm chip resistors. It was assumed in the extraction step that the transmission lines are weakly-coupled, and that the resistance values of all the termination chip resistors are exactly 50 ohms with the second reflections neglected. Comparison of the extracted LRGC matrix components with those from a commercial 3D field solver revealed on average and a maximum relative difference of 2.45% and 7.66%, respectively. In addition, the time-domain crosstalk voltage waveforms in the measured data and those in the SPICE simulation results using the extracted LRGC parameters agreed very well with the average difference and the maximum relative difference in peak crosstalk voltages of 4.15% and 9.68%, respectively.

Analytical GMD formulas for mutual inductance calculation of multilevel interconnects

A set of new analytical formulas is proposed for determining the geometric mean distance (GMD)for use in the Greenhouse method to calculate the inductances of three-dimensional inductors composed of on-chip interconnects. The expressions are derived using a graphical method based on the integral form of the GMD equation. The mutual inductances of coupled interconnects are computed for given layout geometries using the proposed formulas, even when the conductors are partially overlapped in different metal layers. The inductances computed using the formulas agreed well with those generated by an accurate commercial field solver, differing by less than 1% across a variety of the conductor geometries.

A New Inductance Extraction Technique of On-Wafer Spiral Inductor Based on Analytical Interconnect Formula

A new inductance extraction technique of spiral inductor from measurement fixture is presented. We propose a scalable expression of parasitic inductance for interconnects, and design consideration of test structure accommodating spiral inductor. The simple expression includes mutual inductance between the interconnects with high accuracy. The formula matches a commercial field solver inductance values within 1.4%. The layout of the test structure to reduce magnetic coupling between the spiral and the interconnects allows us to extract the intrinsic inductance of spiral more accurately. The proposed technique requires neither special fixture used for measurement-based method nor skilled worker for precise extraction with the analytical technique used.

Discharge energy available to grounded spheres approaching charged ground-backed insulators

Programming a commercial electrostatic field solver has enabled the accurate calculation of the field distribution existing within the air gap between a charged insulating sheet with a grounded backing and a grounded conducting sphere. These data are input into a computer program which uses a breakdown criterion to determine if the field conditions are sufficient to initiate a discharge between the sphere and the insulator. The presence of the insulating sheet has the effect of significantly increasing the electrostatic field which can be sustained prior to electrostatic discharge (ESD) between the conductor and charged insulating sheet compared to that for a similar sphere and conducting sheet system. A further computer program enables the determination of the stored electrostatic energy due to the presence of charge on a ground-backed insulating sheet. Results show the maximum available energy calculated over a defined area of the charged surface to be significantly dependent on the insulator thickness, relative primitivity and surface voltage. The obtained data can be considered in terms of the posed ignition risk to a surrounding flammable atmosphere which is useful for the determination of potential electrostatic hazards for a given geometry and charge level.