Average Absorption Coefficient Measurement of Arbitrarily Shaped Electrically Large Objects in a Reverberation Chamber

It is shown in this letter that the average absorption coefficient (AAC) of an object under test (OUT) can be obtained by comparing the measured absorption cross section (ACS) of the OUT with the ACS value of a perfect absorber of the same shape. The ACS of an arbitrarily shaped electrically large perfect absorber can be obtained numerically. Measurements are performed to demonstrate the proposed method. Results show that the AAC is not sensitive (but not independent) to the shape and size of an electrically large absorber. The procedure proposed in this letter can be used to characterize the electromagnetic wave absorptive and scattering ability of arbitrarily shaped objects. A system-level AAC could be very useful for many applications.