Purpose -The purpose of this study is to develop and compare two methods of determining the total field, including phase information, when only field amplitudes have been measured on a set of planes in the near field of a complex electromagnetic source. Design/methodology/approach -The first method is a gradient-based optimization algorithm, based on the adjoint fields. The second method employs an optimization algorithm based on the phase angle gradients of a functional. Findings -The first method, the adjoint field method, is functioning well for a 2D test case. The second method, the phase angle gradient method, gives very good results for 3D test cases.Research limitations/implications -The next step is to test the methods with results from real measurement data. Practical implications -The developed methods are intended for use in dosimetry studies and other applications, where the field distribution from electromagnetic sources are needed. Originality/value -The methods extend previously made constant phase approximations. The present methods are useful in situations where the electromagnetic source is hard to model.

A 3D subgridding technique is used to model the specific absorption rate (SAR) distribution in the isolated cochlea exposed to mobile phone radiation at 1750 MHz using the FDTD method. The cochlea is modeled using an increasing spatial resolutions of 1, 1/3, 1/5, and 1/7 mm. First simulations were performed at 1 mm spatial resolution. The numerical resolution was then increased to 1/3, 1/5, and 1/7 using subgridding without changing the spatial resolution. A second set of simulations was then performed when both the spatial and numerical resolution were increased together. From the obtained results, we conclude that subgridding is important only when both the numerical resolution of the computational grid and the spatial resolution of the model are increased together.

A detailed dosimetry in the inner ear is performed using the FDTD algorithm with a subgridding method. A head model is exposed to a mobile phone radiation and the electromagnetic field in the region of the inner ear is computed with increased numerical resolution by factor of 3, 5 and 7. Results show that increase of the numerical resolution without increase of the geometrical resolution does not give more detailed SAR distribution in the inner ear. Therefore a new model of the cochlea with increasing the geometrical resolution from 1 mm to 1/7 mm and dosimetry in this model is presented.

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