ABsorbing Boundary Conditions

My friend scan someone help me bout Gerrit Mur's boundary conditons, I have written a program with second order approximation in 3D but exactly on the boundaires my program is not absorbing namely still some amount of wave is not abosrbed can anyone tell me does second order approximation of the ABCs of Gerrit Mur abosrb completely the scattered field please help me ? If you have written code just for a free air can you shot it us

Hello,

i am wondering about the time domain special solver setting in CST microwave studio:
ABSORBING HIGHER ORDER MODES AT PORT REGION,
the VBA method is
UseOpenBoundaryForHigherModes = TRUE/FALSE


Could somebody explan what it is, i think it has to do with MUR boundary.
I actually dont know what happens, if there is a mode travelling onto the waveguide port, which is not considered at this port by definition.....

Thanks for any reply.