Electromagnetic Analysis MethodFinite Difference Time Domain (FDTD) The Formulation of FDTD method begins by considering the differential form of Maxwell’s two curl equations that

govern electromagnetic propagation:

From the first equation, it can be seen that the change in the E field (the time derivative) is dependent on the change in the H field across space (the curl operator). This reduces to the basic FDTD equation that the new value of the E field is dependent on the old value of the E field (hence the difference in time) and the difference in the old value of the H field on either side of the E field point in space. Similarly, the new value of the H field is dependent on the old value of the H field (hence the difference in time), and also dependent on the difference in the E field on either side of the H field point.

Computational Domain In order to use FDTD, a computational domain must be established. The computational domain specifies the “space”

within which the simulation will be performed. The space will be divided into grid cells, each having the same size or variable size, and E and H fields will be determined at each cell within the computational domain. Furthermore, the material of each cell must be stated for simulation. Typically, the material will be free-space, metal, or any material for which the permeability, permittivity, and conductivity values can be specified.

Available Academic/Commercial Software There are indeed several codes that are capable of performing FDTD simulation. One of which has been a research

project conducted by Dr. M. Okoniewski from the University of Calgary. This code requires high-speed computational facilities available on WestGrid, which is a collaboration of high performance computing, and networking computers separated geographically, but linked together to act as a “massive computer”. Other codes include CST Microwave Studio, which is generally accepted in the industry as “The Tool” when FDTD computation is called upon. However, as FDTD simulation often requires tremendous amount of time to perform, we turn to Dr. Okoniewski’s code for this project. Furthermore, as opposed to the fixed functionality that a commercial code such as CST Microwave Studio provides, Dr. Okoniewski’s code may be modified with ease, and can be made more tailored to our needs when required.

Background information and Motivation Wireless environments are becoming increasingly prevalent in our modern world. In the case of automobile

bodies, an effective internal antenna system design based on the internal electric field (IEF) distribution is essential for the optimization of a wireless system within the vehicle. Electric field distribution is dependent on the window aperture size, receiving wave frequency and its incident angle. In a previous study, two valuable models were developed. The Microwave Simulation Model is an electromagnetic anechoic chamber that is used to measure a miniaturized automobile with large window apertures in the 4 GHz waveband. The Box-Type Model, on the other hand, is a resonant cavity that measures the internal electric field distribution. Both models yielded a linear relationship between the IEF distribution and cavity modes. In this study, we hope to determine and improve antenna coverage in an automotive environment. From earlier studies, we learned that both the vehicle structure and multiple-frequency electromagnetic fields strongly influence the performance of an automobile antenna. As a result, several calculation methods have been applied to solve differing factors – the Method of Moments Technique has been used to determine the inductance and capacitance of wires, and the Transmission Line Technique for current distribution. Finite Difference Time-Domain method has shown to be a very viable method for the analysis of complicated structures, such as air planes and vehicles. Having reviewed all previous works on this subject, we hope to determine an ideal location for various antennas on a vehicle based on calculations generated by the Finite-Difference Time-Domain (FDTD) method.

WLAN/WPAN Coverage and Reliability in Automotive Environments Joanna Ma, Nima Mahanfar, Colin Ng, Gilson Weng

Supervised by Dr. D. Michelson

University of British ColumbiaDepartment of Electrical and Computer Engineering

Radio Science LabRadio Science Lab

Project descriptionThe introduction of wireless communications to Automotive industry has created new applications like vehicular WLAN. Much promising work has been done and reported in modeling of radiowaves in free space or living spaces, but just a little and insufficient amount of research is reported about Propagation in Cars.Regarding the Electromagnetic interference, vehicular environments are considered as one of the most polluted and hard ones to treat with. The wiring system, engine explosion pulses, sensors, ECU, the mechanical instability of the whole structure along with drastic changes in ambient condition (temperature, humidity, etc,..) is the source of this complexity in dealing with EM in vehicles. Besides, due to the mobility, the outside environment of a vehicle is varying with time, that exponentially increases the complexity.One major goal through such a research is investigating the field distributions inside a vehicle, in the present of all different interference sources. This way, we could have a better understanding the propagation phenomenon and the potential obstacles of utilizing Wireless modules, like Bluetooth, inside a car.Furthermore, this modelling would allow us to determine the contribution of each source to the whole EM fields. The result of such an investigation could be a parametric model which can be used in any automotive design.Different shapes of antennas produce different radiation patterns in space. So, the better choice of the antenna is a necessary step for any design purposes. Different types of antennas are modeled to check out which one is the best compromise for the better coverage and less interference.

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EMC measurment of a vehicle

Commercial antennas for vehicles

Field distributions inside vehicles

FDTD grid

The vehicle structure is discretized

ResultsSetting-up the EM field analysis tool in the which will run on very fast computers provided by WestGrid would be the first phase of this project. To this end, A user manual would be prepared in order to let the future users get started without facing similar problems as it has appeared at the start up. With the aid of EM Field Solver, we will discover Field Distributions of antenna in different positions within a vehicle. The performance of different types of antenna such as patch and dipole in terms of coverage, power efficiency, and sensitivity will also be found out. At the end, some suggestions on the optimum location for the installation of WPAN antennas within an automobile for different applications will be proposed. We will also discuss what challenges we faced during this research and what can be done to make future research on this project more efficient and successful.