Analytical methods for near field radio frequency dosimetry for tissue layers and celluar structures
Creators: name: Kurniawan, Teddy
Publisher: name: Swinburne
Year: 2024

description: Investigations into the possible health effects of mobile phone emissions, particularly as the phones are placed in close proximity to the human body, are increasingly relevant in light of the rapid growth in mobile phone use. The International Committee on Non-Ionizing Radiation Protection (ICNIRP) has noted the need to address near field exposure beyond the plane wave or far field approach, although the latter is considered to be conservative and sufficient for many cases. These cases include the exposure of object of a relatively higher permittivity (such as human muscles), or for objects located at certain distance where the magnitude of the normal component electric field (high for small distance between the object and exposure source) starts to become insignificant. However, these cases are not always representative for an antenna in close proximity of human body, or for a human body consisting of varied dielectric properties. A need exists for appropriate analytical methods to complement the currently available techniques in Radio Frequency (RF) dosimetry, including computational methods. Furthermore, the availability of analytical methods can be extended to investigate micro-level (cellular level) aspects of RF dosimetry, which is rarely being addressed and not well related to the macrolevel aspects of RF dosimetry. This thesis aims to fill some of the knowledge gaps around comprehensive quantification of RF energy when absorbed by the human body, in particular exploring near field exposures. Under such conditions, the normal component of induced electric fields is significant in objects located at close proximity to an RF radiating source. A simple yet comprehensive analytical method to study induced electromagnetic field in the layered half-space dielectric adjacent to a dipole is presented. The analytical method, of closed-form and high degree of accuracy, is able to provide intuitive understanding of energy absorption mechanism in near field RF exposure. A quantitative description can also be achieved with less time and computing resources. These are advantages that cannot be obtained from numerical computations only. In particular, a novel reconciliation theory is introduced, to describe the relationship between the incident free space fields and the induced fields in a non-magnetic lossy dielectric. This novel method is developed through the use of an extention of formulae of Balanis, with introduced scaling factors to compute the incident fields in the free space between a dipole and a layered half-space dielectric. The scaling factors are required since the original Balanis formulae is used only to compute the incident free space fields without the presence of an object near the dipole. In addition, the developed analytical method can be extended to compute the induced membrane potential of a model of a cell structure, located in a layered half-space dielectric adjacent to a dipole. This, for the first time, allows macro-level analytical methods to be applied to a micro-level dosimetry problem, using suitable parameters to describe the radiating power of a Global System for Mobile Communications (GSM) phone.