WLAN/WPAN Coverage and Reliability in Automotive Environments
Joanna Ma, Nima Mahanfar, Colin Ng, Gilson Weng
Supervised by Dr. D. Michelson
Radio Science Lab
University of British Columbia
Department of Electrical and Computer Engineering
Project description
Electromagnetic Analysis Method
The 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.
Finite 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:


Commercial
antennas for
vehicles
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.

H
  E  
t
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.
FDTD grid
The vehicle
structure is
discretized
Results
Setting-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.
Field distributions
inside vehicles
EMC measurment of a vehicle

E
 H 
t