Antenna Performance Analysis for the Nationwide Differential Global Positioning

by Barton, Ian M.

As part of ongoing efforts to improve the Nationwide DGPS (NDGPS), an Antenna Performance Analysis (APA) is conducted by Ohio University for the U.S. Coast Guard (USCG) with the assistance from the U.S. Department of Transportation Volpe Center. The APA conducted has four main parts: 1) generation of generic measurement accuracy vs antenna performance mapping function using a multipath model; 2) collection of antenna anechoic chamber radiation patterns; 3) prediction of NDGPS installed multipath performance using the multipath model, a reflection model, and measured antenna performance data; and, 4) field data validation, for the predictions in step 3. Five commercially available GPS antennas were selected by the USCG for assessment. The various trade-offs in system performance are discussed in this thesis, including the gain uniformity across the coverage volume and the ability to calibrate timing errors inherent in the antenna. The antenna anechoic chamber measurement accuracy is also considered as part of this research effort.