Yazılım Tabanlı Gps Almaçlarının İncelenmesi
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This study aims to investigate software based GPS receivers. In order to investigate software based GPS receivers, GPS system concepts, GPS signal structure and GPS receiver structure are studied. MATLAB models are implemented for each GPS receiver part and their performances are evaluated. These software implemented models are used with real recorded GPS signals to determine the receiver position. For acquisition, two methods are modeled and tested: FFT method and the delay and multiply approach. The tracking contains two parts: code tracking and carrier frequency tracking. Carrier frequency tracking has been implemented by a kind of PLL named Costas Loop and code tracking has been implemented by a kind of DLL named early-late tracking loop. The navigation message has been decoded and pseudoranges have been calculated using tracking results. Receiver position has been determined via the least-square method.