Electromagnetic Coupling between Mobile Wireless Devices and Wiring Systems

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EMC Europe Workshop 2005
Electromagnetic Coupling between Mobile Wireless
Devices and Wiring Systems in Vehicles Yaping
Zhang, John Paul, Christos Christopoulos (
George Green Institute for Electromagnetic
Research University of Nottingham, Nottingham NG7
2RD, UK )
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Outline

• Evolution of the Mobile Phone Technologies
• Concerns over the Mobile Phones Adversary
• Effects and positive Solution
• Simulation Configurations and Simulation Models
• Simulation Results
• Conclusions

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Evolution of the Mobile Phone Technologies

• Over the last two decades, mobile phones have
  evolved from simple single-channel two-way radios
  and text messaging devices to advanced
  multifunctional multimedia and entertainment
  marvels.
• In recent years, wireless communication has
  experienced an explosive growth globally,
  considerable worldwide interest in the
  development of nomadic wireless devices brought
  about a new generation of 3G mobile phones and
  related networks.
• The new generation mobile phones not only
  support the basic voice service in multiple
  frequency bands, but also support high-speed
  data, multimedia applications, global positioning
  system (GPS) location technology and Bluetooth
  (BT) wireless connectivity.

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Concerns Over the Mobile Phones Adversary
Effects and Positive Solution

• CONCERNS
• Adverse direct coupling to, and possibly
  malfunctioning of, the control, sensor and
  communication devices interconnected through
  cables and wires.
• Adverse impact on the electromagnetic (EM) noise
  floor of environments densely populated with such
  devices.
• POSITIVE SOLUTION
• It is highly desirable to assess the level of
  coupling between such systems and therefore offer
  the capability to designers of estimating the
  risk of malfunction and the effectiveness of
  proposed remedies using computer aided design
  (CAD) tools.

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Introduction to the Simulations

• Simulations of mobile phone electromagnetic
  coupling to a typical long thin wire inside a
  vehicle were carried out for the cases with and
  without a passenger.
• Results presented in this paper are obtained at
  mobile phone frequency of 900 MHz by sinusoidal
  excitation, and compared with Fast Fourier
  Transform (FFT) analyses of the electromagnetic
  coupling of a dipole antenna to a thin wire
  excited by a Gaussian source, with a halfwidth of
  0.556 ns. .

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Introduction to the Simulations (I)
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Configuration of a Simulated Vehicle
Fig. 1 Schematic configuration of a simulated
vehicle
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Introduction to the Simulations (II)

• A thin wire, 5 m long, of 2 mm diameter, is
  parallel to, and 5 cm from the top plane of the
  vehicle. It is open at one end and terminated by
  a load of 150 Ohms at the other to the top plane.
  The wire junction is 1 m from the back plane on
  the origin side ( Fig. 2).
• A passenger with a mobile is sitting underneath
  the thin wire, with the mobile antenna
  perpendicular to the thin wire. The center of the
  dipole is 18 cm directly below the thin wire
  junction end. The passenger is located centrally
  above the bottom plane of the vehicle in the
  z-direction, facing the front in the x-direction
  (Fig. 2).
• The mobile phone is held against the ear. The
  cross section of the simulation model in the
  y-direction is schematically shown in Fig. 2. The
  cross section of the simulation model in the
  x-direction is schematically shown in Fig. 3.

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Cross section of the simulation model in the
y-direction
Fig. 2 Cross section of the simulation model in
the y-direction
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Cross section of the simulation model in the
x-direction
Fig. 3 Cross section of the simulation model in
the x-direction
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Introduction to the Simulations (III)

• Simulations are carried out on a Compaq ES45
  Workstation with 1.2GHz CPU, Running TRU64 UNIX.
• For the TLM simulation results presented in this
  paper, the mesh size is chosen as 1.67cm. The
  numbers of nodes are Nx360, Ny120, Nz180.
• The numbers of time steps for a sinusoidal and a
  Gaussian excitations are NT16000, and NT16384,
  respectively.
• The typical calculation times for a Sinusoidal
  and a Gaussian excitations are 388126 seconds and
  417564 seconds, respectively.

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Simulation Results by Using of 900 MHz Sinusoidal
Excitation Source (I)
The voltages across the load with and without a
passenger inside a vehicle are shown in Fig. 4
(a) and (b), respectively.
(a)
(b)
Fig. 4 Voltages across the load inside a
vehicle (a) with a passenger (b) without a
passenger.
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Simulation Results by Using of 900 MHz Sinusoidal
Excitation Source (II)
The magnetic field distributions in the x-y plane
inside a vehicle with and without a passenger are
shown in Fig. 5 (a) and (b), respectively, with
the range of 40 dB from peak to minimum in the
plots.
Fig. 5 The magnetic field distributions in the
x-y plane inside a vehicle (a) with a passenger
(b) without a passenger.
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Simulation Results by Using of 900 MHz Sinusoidal
Excitation Source (III)
The maximum currents along the thin wire for the
cases with and without a passenger inside a
vehicle are compared and shown in Fig. 6.
Fig. 6 Comparison of the maximum currents along
the thin wire .
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Simulation Results by Using of 900 MHz Sinusoidal
Excitation Source (IV)
The maximum currents along the thin wire for the
cases with and without a passenger, and with 4
passengers in front of each other in Fig. 2 with
50 cm space between them inside a vehicle are
compared and shown in Fig. 7.
Fig. 7
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Simulation Results by Using Gaussian Excitation
Source (I)
The voltages across the load with and without a
passenger inside a vehicle are shown in Fig. 8
(a) and (b), respectively.
(a)
(b)
Fig. 8 Voltages across the load inside a
vehicle (a) with a passenger (b) without a
passenger.
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Simulation Results by Using Gaussian Excitation
Source (II)
The ratio of the FFT voltage across the load, to
the FFT voltage at the gap of a dipole as a
function of frequency, for the cases with and
without a passenger inside a vehicle, are
compared and shown in Fig. 9.
Fig. 9
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Simulation Results by Using Gaussian Excitation
Source (III)
The ratio of the FFT voltage across the load, to
the FFT voltage at the gap of a dipole as a
function of frequency, for the cases with and
without a passenger, and with 4 passengers inside
a vehicle, are compared and shown in Fig. 10.
Fig. 10
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Conclusions

• Electromagnetic couplings of a mobile phone to a
  typical long thin wire inside a vehicle are
  simulated for the cases with and without a
  passenger inside a vehicle.
• Simulation results are further compared with
  those of 4 passengers inside a vehicle.
• Materials with electrical properties resembling
  those of humans inside vehicles are described.
• Very long run time has been used in the
  simulations for both Sinusoidal and Gaussian
  excitations in order to achieve convergence.
• Simulation results show that the passenger
  inside a vehicle has some impact on the level of
  the electromagnetic coupling of a mobile phone to
  a typical long thin wire.