Calculating the absorption diagram of a ground plane in CST Studio 2008

Hi,

I would like to calculate the absoprtion diagram of a ground plane in first for next use the method for another structure.

I'm working with CST Microwave Studio 2008.

I have a plane wave at z=13mm and a probe a z=12mm.

------------ plane wave

o probe

--------------
|-------------| ground plane
---------------

I simulate with the temporal solver for the ground plane in vaccum (that's not a ground plane now but just a block of air to have module and phase of the incident wave)

Then I make another simulation with the ground plane (it's a PEC material now) to have the reflection wave.

Now I have module and phase for incident and reflected wave.

The absorption diagram can be determined by:
Absorption = ReflectedWave - Incidentwave

where

ReflectedWave = (Module_linear_reflected).*exp(i*phase_degrees_ref lected*pi/180);

IncidentWave = (Module_linear_incident).*exp(i*phase_degrees_inci dent*pi/180);

When I plot the absorption diagram in dB by 20*log10(abs(Absorption)), I don't have a 0 dB absorbed.


I don't know where is my mistakes and what to do to obtain this diagram.

Thank you for your help and sorry for my english (I need to improve it)

All the best,

Piboo