Juliano Fujioka Mologni

Simulation of the enhancement factor from an individual 3D hemisphere-on-post field emitter by using finite elements method.

This paper presents a 3D computational framework for evaluating electrostatic properties of a single field emitter characterized by the hemisphere-on-post geometry. Numerical simulations employed the finite elements method by using Ansys-Maxwell software. Extensive parametric simulations were focused on the threshold distance from which the emitter field enhancement factor (γ) becomes independent from the anode-substrate gap (G). This investigation allowed demonstrating that the ratio between G and the emitter height (h) is a reliable reference for a broad range of emitter dimensions; furthermore, results permitted establishing G/h ≥ 2.2 as the threshold condition for setting the anode without affecting γ.

Numerical study on performance of pyramidal and conical isotropic etched single emitters

Abstract A full three-dimensional model was implemented in order to investigate the electrical characteristics of conical and pyramidal isotropic etched emitters. The analysis was performed using the finite element method (FEM). The simulations of both emitters were modeled using a combination of tetrahedral and hexahedral elements that are capable of creating a mapped and regular mesh in the vacuum region and an irregular mesh near the surfaces of the emitter. The electric field strengths and electric potentials are computed and can be used to estimate the field enhancement factor as well as the current density using the Fowler–Nordheim (FN) theory. The FEM provides results at nodes located at discrete coordinates in space; therefore, the surface of the emitter can be generated through a function interpolating a set of scattered data points. The emission current is calculated through integration of the current density over the emitter tip surface. The influences of the device geometrical structure on its potential distribution, electric field and emission characteristics are discussed.

Automotive EMC analysis using the hybrid finite element boundary integral approach

The majority of innovative trends in automotive industry today relies on electronic systems. Understanding the electromagnetic behavior of the electronic control units (ECUs) in a vehicle has become an ever increasing concern of automotive manufacturers. Computational Electromagnetic Modeling (CEM) is a cost effective approach that has being adopted by the automotive industry to address electromagnetic compatibility (EMC) problems. Automotive structures are electrically large in nature and the systems required for a complete EMC analysis can be fairly complex. For this reason, there is no single numerical technique that can be used to address all automotive EMC problems. This paper shows how the automotive standard ISO11452-2 can be solved using the hybrid Finite Element Boundary Integral (FEBI) approach. A comparative study indicates that FEBI is faster and requires less computational effort than the Finite Element Method (FEM) for this particular analysis. Recent technology advances on FEBI are also presented showing the great potential of this technique to address automotive EMC problems.

Comments on the FCC approval of finite element method for biomedical transmitters

The Federal Communications Commission (FCC) ruled on February 1st 2011 that the finite element method (FEM) is a valid technique to simulate transmitters that are placed inside, on the surface, or near the human body. This paper investigates how FEM can be employed on biomedical engineering. A complete high fidelity human body model including frequency dependent materials and complex geometries was used. Three examples are described including a magnetic resonance imaging (MRI) system, a human body on a substation environment and specific absorption rate (SAR) simulations on a human head due to a cell phone radiation. Advanced multiphysics technology coupling electromagnetic and thermal simulations are also addressed. A very good agreement between FEM simulations and measurement data was achieved for SAR calculations.

Accelerating the Vehicle Development Process by Employing EMI and EMC Numerical Analysis Assisted by High Performance Computing

Since the majority of the innovative trends in automotive industry today are based in advanced electronics technology, mastering the EMI (Electromagnetic Interference) between embedded electronic subsystem and the EMC (Electromagnetic Compatibility) features of a vehicle in its early design phase becomes one of the crucial technical challenges faced by all automotive manufacturers. Even if all electronic subsystems in a vehicle are validated under the EMC standards, the integration between them may create numerous points of potential hazards that affects the total electromagnetic behavior of the entire system, hazards that can be detected only once the first complete prototype is available, and whose resolution at this phase of the process is very time consuming and expensive. This paper presents the state of the art regarding electromagnetic numerical analysis using Ansoft HFSS (High Frequency Structure Simulator) tool and a parallel HPC (High Performance Computing) consisting of numerous computer nodes connected to a network. An application of this approach to a vehicle modeling is presented. Adaptations to CAD (Computer Aided Design) models are proposed in order to improve CAE (Computer Aided Engineering) analysis and save computer effort with the objective to reach a correct level of industrial efficiency. EMI between subsystems are investigated using field solvers and a SI (Signal Integrity) analysis is performed in a wiring harness transmitting a random CAN J1939 standard signal. A complete analysis on EMI and EMC properties is performed, and a conclusion concerning the practical use of numerical simulation at early stages of the vehicle design is proposed.

Full Vehicle Electromagnetic Simulation Using the Hybrid Finite Element Boundary Integral Approach

Perry, T.S., Geppert, L., Do portable electronics endanger flight? the evidence mounts (1996) IEEE Spectrum, 33, pp. 26-33. , September

Conformity evaluation of radiated immunity standards to modern telecommunication services using statistical techniques

Telecommunication services have faced significant improvements along the last decades, mainly related to new modulation techniques. Consequently, signals waveforms have gradually been modified. In this scenario, Electromagnetic Compatibility and, specially, Radiated Immunity tests became necessary to ensure the performance of electronic devices when exposed to such signals. Considering that the waveforms and modulations specified in Radiated Immunity standards are much simpler than those currently used in Telecommunication services, a statistical study about the impact of this difference is proposed for the 210–216 MHz frequency range.

Signal Integrity Considerations Applied to Automotive Grounding System's Design

Designing electric circuits which have the vehicles body as a part of the currents path is a common practice in the automotive industry. In this case, the signal integrity is affected by many variables, e.g. the bodys shape and its constituent materials. Nevertheless, the design of the vehicles body is generally based only on esthetic and aerodynamic factors and signal integrity is not taken into account. This is not a great concern anyway, since this kind of signal usually comes from power supply and the electrical and electronic devices might work (at least partially) even with a voltage level decrease. However, although power supply signals are theoretically continuous, higher frequency components can be noticed through measurements. Besides that, the implementation of Power Line Communication system in vehicles is being studied lately, which means that the traditional power lines would also carry information signals, with associated high frequency content. These observations lead to a concern about the bodys behavior when conducting higher frequency currents, since it is not considered for the design of the vehicles grounding systems. In this case, it is desirable that these spurious frequency components have a minimum impedance path to the batterys negative pole. This goal can be achieved by calculating optimal points for the grounding points. However, this is not an easy task, since there are no analytical equations for the impedance in this case. Hence, this paper proposes the use of the Genetic Algorithm as a tool for numerically calculating the best grounding points in a vehicle, through the electromagnetic simulation software ANSYS HFSS®.

Wireless sensor network analysis using the finite element boundary integral numerical technique

Wireless sensor technology is becoming a practical replacement to the conventional wired sensors primarily due to the easiness of implementation and cost reduction. In spite of that, process industries are not still using such kind of solution in large scale due to lack of field-proven data related to robustness and reliability of the communication link. A wireless sensor network (WSN) consists of spatially distributed independent sensors that are connected to a wired gateway. The present study shows a full wave simulation of a WSN installed in a subsection of a refinery coupled to a circuit simulator that generates electric wave forms according to IEEE 802.11 specification. The finite element boundary integral (FEBI) approach, which is now commercially available in Ansys HFSS, was used to solve the electromagnetic model. The advantages of FEBI for solving very large field problems are presented and the simulation results were compared to the finite element method (FEM) and the method of moments (MoM). The integration of a 3D field solver and a circuit simulator enables the calculation of radiation patterns, electric field plots, bit error rate, constellation plots while incorporating the actual transmitter and receiver antennas and the electrical schematic of the sensors and gateway. The purpose of this simulation is to investigate the limitation of the technology, help engineers to create best practices for WSN installation and to give an approach for the optimization of gateways positioning.

FR-4 waveguide electronic circuits at 10 Gbit/s

A 10-Gbit/s interconnection using a FR-4 Substrate Integrated Waveguide (SIWG) and ASK and QAM modulation format is evaluated as a new alternative for high-speed digital electronic circuits. A set of experimental and simulation results obtained is evaluated, showing far than satisfactory performance.