Abstract
In this paper we present a computational electromagnetic model for tree scattering at VHF/UHF frequencies. A structure model with dielectric cylinders is being used to simulate trees with bare branches. The method of moments (MoM) solution of the volume integral equation is computed for the tree scattering signature. An efficient numerical algorithm based on the sparse matrix iterative approach (SMIA) is used to solve the matrix equation. The SMIA decomposes the impedance matrix into a sparse matrix for the near interactions, and a complementary matrix for the far interactions among the cylindrical subβcells of the tree structure. Using a direct sparse solver to estimate the strong interaction part, we iteratively include the weak interaction contribution in order to update the solution. The key feature of the SMIA approach is that very little iteration is required to obtain convergent solutions. We have applied the SMIA tree scattering model to calculate scattering from various simulated trees with up to several hundreds of branches. Solutions obtained from the SMIA method agree very well with the solutions obtained using exact matrix inversion and the conjugate gradient method (CGM). Compared to the CGM, the SMIA approach reduces the number of iterations by a factor of more than a hundred and provides a much faster numerical solution scheme for computing tree scattering. Β© 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 198β202, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11014