The Study of RF Burns and AMI Exposure Using the FDTD Method

Thesis (Ph.D.), School of Electrical Engineering and Computer Science, Washington State UniversityOne of my research topic is about the human body exposure to AMI. Power utilities are increasingly deploying residential meters that communicate wirelessly. These meters may employ multiple antennas and radiate at different frequencies, ranging from 850 MHz to 2.4 GHz. Unlike radiofrequency (RF) exposure caused by cell phones, where the position of the phone relative to the body is somewhat fixed, the position of a power meter relative to the body is rather unconstrained. In this work we use the finite-difference time-domain (FDTD) method to study the specific absorption rate (SAR) produced in full anatomical models of humans when they are exposed to the RF fields produced by a wireless AMI meter. When one accounts for the meter's true duty cycle or there is a realistic separation between the meter and an individual, all SAR values fall within safety limits. Another topic of my research is about the RF burns. Both the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute of Electrical and Electronics Engineers (IEEE) have maximum permissible exposure (MPE) guidelines that specify the limits on the magnitude of the electromagnetic (EM) fields and contact currents to which humans are allowed to be exposed. However, even when the fields do not exceed the ICNIRP or IEEE limits, a radio frequency (RF) burn may occur when a person is in contact with a perfect electric conductor (PEC). In this work we use the FDTD method and a full anatomical model to calculate the contact current density when a person is in contact with a PEC rod that is on order of 2 m in length. The effects of rod length, rod diameter, and the type of touch are considered. Frequencies are between 10 MHz and 600 MHz. A SubGridding technique in FDTD field was investigated as a topic in my thesis. The fundamental FDTD method is not well suited to model problems in which the structure of interest has important geometric features at greatly different scales. In order to study such "multiscale" problems, numerous modified FDTD algorithms have been proposed that incorporate a subgridding technique. In 2006, Berenger proposed a promising new technique known as the Huygens subgridding (HSG) method. However, this technique suffers from a late-time instabilities. In this work, we demonstrate how the judicious use of artificial loss can be used to control this instability. We also explore other aspects of the HSG method, such as the reflection coefficient, for various discretizations.Department of Electrical Engineering, Washington State Universit