User effect on total radiated power and 3-D radiation pattern of mobile handsets

We investigate how the user's body affects the radiation characteristics, i.e., 3-D radiation pattern and total radiated power (TRP) of mobile handsets. In previous studies up to 10 dB difference was found in TRP of a mobile handset between individual users. Our objective is to investigate the reasons for the large differences. Thirteen test persons were measured with an active GSM 900/1800 mobile phone. The standard deviation of the TRP results between the test persons was relatively low when the test persons held the phone in a predefined talk position. The variation in the corresponding results was much larger when the users could freely select the talk position. The variable hand position and the grip on the handset seems to be the major reason for the large differences whereas the anatomical differences between the users play only a smaller role.