Effect of the human body on total radiated power and the 3-D radiation pattern of mobile handsets

We investigate how the user's body affects the radiation characteristics, e.g., radiation pattern and total radiated power (TRP), of mobile phones. We carried out measurements for two Global System for Mobile Communications (GSM) 900/1800 phones with two measurement systems: a 3-D far-field pattern measurement system and the Rapid Antenna Measurement System (RAMS). Up to 13 mobile phone users participated in the measurements. The main. objectives are to study how much the TRP varies between the users and how large an influence the user's hand, particularly its position on the mobile phone, has on the TRP. The contributions of the head and the hand to the total loss are separately studied as well. The standard deviation of the TRP results between the 13 users in the RAMS measurements was relatively low, i.e., less than 1 dB, when the users held the mobile phone in a predefined talk position on the left side of their heads. The standard deviation of the corresponding result was up to 3 dB when the users were allowed to freely select the way to hold the phone. The TRP results for two phantoms agreed well with the average TRP results for the test persons when only the loss contribution of the head was included. Hence, we conclude that the variable hand position and grip on the mobile phone are the main reasons for the large differences in the TRP between the users.