Changes in Handset Performance Measures due to Spherical Radiation Pattern Measurement Uncertainty

An important characteristic of a mobile handset is its ability to receive and transmit power. One way to characterize the performance of a handset in this respect is to use measurements of the spherical radiation pattern from which the total radiated power (TRP), total isotropic sensitivity (TIS), and mean effective gain (MEG) can be computed. Often this kind of measurements are made with a phantom head next to the handsets in order to simulate the influence of a real user. The measured radiation patterns are only expected to be repeatable if the same setup is used, i.e., the same phantom and the same mounting of the handset on the phantom. In this work the influence of mounting errors on the TRP, TIS, and MEG is investigated. Knowledge about the error due to incorrect mounting is necessary in determining requirements for both the mounting accuracy as well as for other parts of the measurement system that may introduce errors in standardized performance measurements. Radiation patterns of six handsets have been measured while they were mounted at various offsets from the reference position defined by the Cellular Telecommunications & Internet Association (CTIA) certification. The change in the performance measures are investigated for both the GSM-900 and the GSM-1800 band. Despite the deliberately large deviations from the reference position, the changes in TRP and TIS are generally within ±0.5dB with a maximum of about 1.4dB. For the MEG values the results depend on the orientation of the handset with respect to the environment. Standard deviations up to about 0.5dB and a maximum deviation of about 1.6dB were found.