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 ) EMC Europe Workshop 2005

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

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. Evolution of the Mobile Phone Technologies

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. Concerns Over the Mobile Phones’ Adversary Effects and Positive Solution

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 ns.. Introduction to the Simulations

Introduction to the Simulations (I) The vehicle is 6m long, 3m wide and 2m high, with 8 windows. One is in the front, one is in the back, and three are on each side in the longitudinal direction (schematically shown in Fig. 1). The front and back windows are 2.33m wide and 1.667m high. The windows on both sides in the longitudinal direction are 1.5m wide and 1.33m high (Fig. 1) The dielectric material properties of the human are selected as. These properties are representative of biological tissues at 900 MHz.

Configuration of a Simulated Vehicle Fig. 1 Schematic configuration of a simulated vehicle

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. Introduction to the Simulations (II)

Cross section of the simulation model in the y-direction Fig. 2 Cross section of the simulation model in the y-direction

Fig. 3 Cross section of the simulation model in the x-direction Cross section of the simulation model in the x-direction

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: Nx=360, Ny=120, Nz=180. The numbers of time steps for a sinusoidal and a Gaussian excitations are NT=16000, and NT=16384, respectively. The typical calculation times for a Sinusoidal and a Gaussian excitations are seconds and seconds, respectively. Introduction to the Simulations (III)

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. Fig. 4 Voltages across the load inside a vehicle: (a) with a passenger; (b) without a passenger. (a) (b)

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. (a) (b)

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.

Simulation Results by Using of 900 MHz Sinusoidal Excitation Source (IV) Fig. 7 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.

Simulation Results by Using Gaussian Excitation Source (I) Fig. 8 Voltages across the load inside a vehicle: (a) with a passenger; (b) without a passenger. The voltages across the load with and without a passenger inside a vehicle are shown in Fig. 8 (a) and (b), respectively. (a) (b)

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 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, and with 4 passengers inside a vehicle, are compared and shown in Fig. 10. Fig. 10 Simulation Results by Using Gaussian Excitation Source (III)

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.