Application of the DGF-FDTD technique to log periodic antennas

The paper compares the computer resource demand, particularly storage, of the discrete Green´s function-finite difference time domain (DGF-FDTD) method, and of the traditional FDTD (using a Cartesian grid). The formulation of the DGF-FDTD is explained in some depth. The comparison of required storage between the two simulation techniques is conducted using a worked example; this shows that DGF-FDTD offers a significant reduction of demand, the FDTD requirement being 366.2 Mbytes as opposed to less than 1 Mbyte for DGF-FDTD. The DGF-FDTD, while it requires considerably less storage, does have some computational overheads, in particular for the calculation of the Green´s functions. Using the fact that the Green´s function from A to B is the same as its reciprocal reduces the number of Green´s functions to be calculated. An anticipated use of the DGF-FDTD technique is one in which the advantages of the FDTD method are employed to the best advantage, that is to model a complex source, while the homogeneous area between the source and the target is modelled using DGF-FDTD.