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This paper describes and validates a technique to characterize the environmental effects on mobile terminal GPS antennas using statistical model. This method requires the knowledge of 3-D free space antenna gain patterns and average angular distribution of incident power in the environment. The power distribution must be known in both elevation and azimuth and separately for parallel and perpendicular polarizations. The antenna performance is assessed in terms of GPS Mean Effective Gain (MEGGPS) and GPS Coverage Efficiency (ηc). Angle of Arrival (AoAGPS) distributions of incident GPS radio waves arriving at the mobile terminal are assumed to be randomly uniform in both the azimuth and elevation planes. It effectively replicates the open field (sub-urban) working conditions for the mobile terminal GPS antennas. The method could be adapted to an urban environment by introducing the information of AoAGPS distributions. A lengthy open field measurement campaign based on received signal-to-noise ratio (SNR) and mean number of tracked GPS satellites is carried out to validate the statistical model.
Date of Publication: Feb. 2012