Absorption cross section (ACS) of an object is used in stochastic power balance models, while human ACS is closely related to microwave dosimetry parameters such as specific absorption rate (SAR) and thus characterises exposure as well as effect of human bodies on multipath propagation. ACS, averaged over all directions of incidence, can be obtained in the frequency domain from the S-parameters of two antennas in a stirred-mode reverberation chamber; however, our new time domain method is faster, avoids the need to determine antenna efficiency, and has been validated with a test object of calculable ACS. We can now measure human ACS from 1 to 18GHz, to within 3%, in under 10 minutes. We have done this for 48 subjects, and explored correlations between ACS and body parameters including mass, height, surface area and subcutaneous fat thickness.
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