Use of second order absorbing boundary conditions for the termination of planar waveguides in the FDTD method

The necessity of using effective absorbing boundary conditions (ABCs) to terminate microstrip or other planar waveguides in the FDTD method has long been appreciated but, until recently, little attention has been given in the literature to the best choice of ABC algorithm for this purpose. Although some comparisons of ABCs are now available they, unfortunately, differ in their conclusions. The authors compare the theoretical and numerical behaviour of some published ABCs and the best ABC algorithm for this application is identified.