Questions about setting up standard reference EM field

hi,all: I am getting into a project to setup standard reference EM field from 18 GHz to 40 GHz. 1.Could anyone tell me the difficulty and difference between that and below the 18 GHz? 2.Is there any new method? 3.What special advice and instruments are needed? 4.Could anyone help me get the do

carbon-impregnated foam pyramids

Hello group, Does anybody know how to measure the absorption characteristics of the carbon-impregnated foam pyramids? And is there any standard related to this? Thanks in advance. Lucian Yau