The antenna to be analyzed is modeled by a set of cubic cells. Choosing an appropriate number is an art. Similarly, it will be necessary to have a meshing program. Using a two-dimensional model will greatly reduce computer storage and run time. Remember that our purpose should be to gain insight unavailable from measurements. The calculations require the storage of three components of both the electric and magnetic fields in each Yee cell. Because we solve the problem in the time domain, the components are only real numbers, unlike frequency responses, which use complex numbers for each component. The material properties of the cells can be indicated with short 1- byte integers provided that there are no more than 256 different ones. Single-precision storage of the components requires 30 bytes for each cell; double-precision storage requires 54 bytes. A three-dimensional problem with 200 cells on a side contains 8M cells and would need 240 Mbytes of storage for single-precision and 432 Mbytes for double-precision components.
At each time step approximately 10 floating-point operations (flops) are needed for each component in each cell. We must run the time steps until the input pulse has peaked and died out in each cell. This takes about 10 times the number of cells in the longest direction (maximum number along one axis). The three-dimensional problem with 200 cells on a side runs for 2000 time steps and requires 60 flops times the number of cells. The solution needs 2000 × 8M × 60 flops = 960 Gflops for completion. |
