A multiregion integral-equation method for antennas implanted in anatomical human models

To aid the design of power- and spectrum-efficient implanted antennas, efficient computational methods that can account for the presence of nearby inhomogeneous and dispersive human tissues are needed. While layered planar or spherical tissue models are often used to represent the antenna environment, the increasing fidelity and availability of anatomical human models can enable site-specific modeling, more accurate analysis, and better designs. Simulating radiation from antennas near/on/in anatomical human models, however, gives rise to large-scale problems as the latest high-fidelity models are composed of over 100 million voxels (J. W. Massey et al., 34^th Annu. Conf. Bioelectromagn. Soc., June 2012). Such large problems can be solved by coupling the surface and volume electric-field integral equations and using a preconditioned, parallel FFT-accelerated iterative solver (F. Wei and A. E. Yılmaz, USNC/URSI Rad. Sci. Meet., July 2013). Unlike traditional finite-difference time-domain based methods, this approach (i) does not require the antenna model to conform to a regular grid to avoid staircasing errors and (ii) accurately models complex antennas by using irregular meshes. Moreover, as is the case for integral-equation methods in general, it requires meshing neither free space (to propagate fields) nor an extended computational domain (to truncate the problem with local boundary conditions that approximate the radiation condition); therefore, for antennas outside the body, this approach does not require the region between the antenna and the body to be meshed. For antennas implanted in voxel-based anatomical human models (by removing tissue voxels at the antenna site from the human model and inserting the antenna mesh), however, the method becomes impractical because it requires the transition region between the antenna and human tissues to be meshed such that the mesh conforms to both the irregular (triangular/tetrahedral) antenna mesh and the voxel tissue mesh.