RF absorber qualification criteria and measurement techniques

Radio-frequency absorber (RFA) performance evaluation criteria are developed with regard to electromagnetic compatibility test objectives. Measurement techniques are considered which are linked to absorber evaluation criteria and can serve as a basis to develop practical test procedures. It is shown that the RFA evaluation techniques can be related to three levels of RFA evaluation: RFA bulk material, reflecting surface lined by an absorber array, and field uniformity in an absorber lined shielding room. Only the third evaluation level explicitly matches the EMC application specifics; however, it yields narrow-in-scope results which are difficult to expand to other room sizes and shapes and absorber parameters and placements. Together with the low-frequency bulk material and high-frequency time domain reflection evaluations, this method can serve as a useful complementary technique. More general evaluation can be realized using ATS (absorber-lined open-area test-site) site attenuation measurements which result in relatively simple end-user-oriented RFA qualification procedures