On the concept of the transparent absorbing boundary

The transparent absorbing boundary (TAB) was recently suggested for grid te rmination in finite methods. Previously, it was shown that this boundary is matched with free space if the TAB region extends to infinity. In this pap er, reflection from a TAB layer backed by a boundary (electric or magnetic wall) is analyzed both analytically and numerically. It is shown that, alth ough the auxiliary fields can be attenuated in the TAB region to as low a l evel as desired, the reflected wave from the backing boundary is then ampli fied back to the original level of the incident wave. A modification of the Yee algorithm as suggested by the TAB authors is shown to be equivalent to a usual absorbing boundary condition at the truncation interface. (C) 1999 John Wiley & Sons, Inc.