Complex source modeling for electromagnetic dosimetry

Licentiate thesis, 2008

Electromagnetic modeling of complex sources is useful in dosimetry applications as well as for near-field to far-field transformations and antenna diagnostics. In order to determine whether exposure safety guidelines, such as the EU directive 2004/40/EC, are complied with, it is important to be able to model the field distribution from electromagnetic sources. Two methods of determining the total field, including phase information, when only field amplitudes have been measured on a set of planes in front of an electromagnetic source have been developed. The first method, the adjoint field method, is a gradient based optimization algorithm based on the adjoint fields. The second method, the phase angle gradient method, employs an optimization algorithm based on the phase angle gradients of a functional. The methods have been tested with numerical test cases. The adjoint field method is functioning well in 2D and the phase angle gradient method gives good results for 3D test cases. The phase angle gradient method was also tested for measured magnetic flux density with low frequency from a transformer and for electric field with high frequency from a mobile phone. For the cases with measured field the obtained phase angles on the measurement plane closest to the source gave calculated field on other measurement planes that agrees well with measured field. The developed methods are useful for coupling of measured field amplitudes in front of a source, to numerical calculations of the fields inside humans.