I assume you mean rf absorption. I have never done this test, but this is how I would do it. In principle, you connect a four-port directional coupler (dc) to the output of a signal source, and an appropriate antenna to the dc. Boresight the antenna at a right angle to a bare metal wall. Monitor forward and reverse power. Now interpose absorber-under-test between antenna and wall, and repeat. While maintaining the same signal source power, monitor forward/reverse power from dc. The difference in say, reverse power before and after is proportional to the absorbed power.
This test technique should work well when the antenna can be placed close to the wall. The larger the cone (the lower the frequency of absorption), the farther the transmit antenna must be from the wall, and the lower the dynamic range of the test (absorber usually specs out to 50 dB). If the XMIT antenna must be placed far from the wall, then you may need a separate receive antenna which outputs directly into a receiver, without going through the attenuation of the reverse power dc port. ---------- From: "Yao" <y...@ht.rol.cn.net> To: <emc-p...@majordomo.ieee.org> Subject: carbon-impregnated foam pyramids List-Post: emc-pstc@listserv.ieee.org Date: Thu, Nov 11, 1999, 2:27 AM 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
