Studies of Three Different Methods to Estimate the Up-link Performance of Mobile Phone Antennas
Abstract: Antennas play an important role in determining the overall radio performance for wireless communications. If all other radio components perform according to their specifications, the performance of a mobile phone can be entirely determined by measuring the efficiency of its antenna. Poor performance of the mobile phone may result in reduced coverage, lower capacity and dissatisfied users. Hence, the ability to accurately and efficiently estimate the radio performance of the mobile phone antenna is of great importance to the telecommunications industry.The mobile phone was originally a simple device that only transmitted voice, but it has evolved into a complicated terminal for high data-rate services. This evolution poses many new challenges to mobile phone antenna manufacturers. Antennas must be tested during design and production phases to optimize the in-network radio performance. Standardization bodies, such as the Cellular Telecommunications and Internet Association (CTIA) and the Third Generation Partnership Project (3GPP), have specified procedures for comprehensive testing of the up-link and down-link radio performance of the mobile phone, characterized by the total radiated power (TRP) and total isotropic sensitivity (TIS), respectively.In this thesis, three methods for estimating the up-link radio performance of mobile phone antennas are evaluated: the "EMSCAN Lab Express" planar near field system; the "Telia Scattered Field Measurement method"; and the "Bluetest" reverberation chamber. These methods are compared to the reference CTIA- and 3GPP-approved anechoic chamber methods. Each method is experimentally evaluated by measuring the TRP from a number of commercially available mobile phones and comparing the measurements to the results from a standard reference system. The comparison is performed statistically using simple regression analysis. For the reverberation chamber, the analysis is extended by using simple physical and statistical modeling. In particular, a maximum likelihood (ML) estimator for the Rician K factor is derived, statistically and experimentally evaluated.Based on the results of this thesis, it can be concluded that the EMSCAN Lab Express planar near field method overestimates the up-link performance of mobile phones, thus, introducing an error. The up-link performance of mobile phones estimated by the Telia scattered field measurement method agrees with the reference method, but suffers from problems such as extensive measurement time and poor repeatability. The Bluetest reverberation chamber method estimates the uplink performance of mobile phones well. However, the computed Rician K factor from the ML estimator is found to be greater than zero, indicating an inadequacy in the propagation environment inside the reverberation chamber.
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