On the Influence of the Liquid Type on Mobile Phone Measurements Using Body Phantoms

The measurement campaign described in the previous section included measurements with two different phantoms of the user, a full body phantom and a phantom consisting of a head and a hand. CPK Annual Report 2001 - Figure 4.5.9a (The two phantoms used for the in-network measurements) shows the two phantoms. Both of the tested phantoms are filled with a liquid simulating the human tissue in the sense that the electrical properties of the liquid are similar to that of human tissue. The properties of the liquids are frequency dependent, and therefore they are designed to be used at specific frequency bands, such as 900MHz and 1800MHz for the GSM system. It is customary to use phantoms for specific absorption rate (SAR) measurements where the issue of liquid type is highly important. However, for performance evaluations such as body loss measurements the influence of the liquid type is unknown. The paper [Nielsen, Pedersen, 2001a] focuses on the influence of the liquid on the body loss, and in particular the differences observed when the phantoms are filled with different types of liquids. Three liquids were used, 900MHz SAR liquid, 1800MHz SAR liquid, and a salt/water solution. For the full body phantom it was found that most of the values were within ± 1dB, which is comparable to the confidence intervals of the measurements. For the head/hand phantom, most of the differences found are small, within ± 2dB. Considering the measurement uncertainty it is generally believed that the difference in using the two liquid types is small. Furthermore, all handsets were measured in the anechoic chamber where the influence of the environment is eliminated. From these measurements it was found that the changes in the transmitted power due to the liquid type were less than 1.1dB in all cases. It should be noted that these measurements did not include a hand, which may explain the smaller variation in the measurements. CPK Annual Report 2001 - Figure 4.5.9b (Anechoic room set up for measuring the influence of the phantom liquid. The handset is connected to the GSMtester via the air interface) shows how the handsets are mounted on the phantom in the anechoic room. (Jesper Ø. Nielsen, Gert F. Pedersen)