Use of dual polarization antenna and AGNSS data for timing applications

Global Satellite Navigation System (GNSS) receivers use the time signals broadcast by the satellites for computing position fix and the time offset from the highly accurate satellite clocks. The receiver calculates the range between the receiver and the satellite using time of arrival (TOA) method and applies the principle of trilateration to calculate the position fix and time offset after acquiring the information from at least 4 different satellites. In this thesis work, benefits of using dual feed antenna to improve the timing accuracy of the receiver clock in urban canyons and indoor environments are analyzed. Dual feed antenna is capable of processing information from Line of Sight (LOS) signals received directly from the satellites as well as the reflected signals from the surfaces such as metallic objects, building edges and so on. These signals are fed separately to two different receivers, which compute the position and receiver clock offset, respectively. The computed time offset from both the receivers are compared and analyzed in different location environments with weak or insufficient GNSS signal strengths. Additionally, the benefits of providing assisted GNSS (AGNSS) data to GNSS receivers to reduce the time to first fix (TTFF) in such locations are analyzed. The use of assist data allows the receiver to obtain the necessary satellite information alternatively without having to download those information from the GNSS signals. This reduces receiver’s time to make position fix significantly in challenging locations with insufficient and weak signal strengths. The TTFF with and without the use of AGNSS data are compared