Overview of GPS Overview of Receivers Current Projects Patents Datasheet Preliminary work Schedule of tasks
L1 Carrier wave 1575.420MHz C/A code 1.023MHz Satellite Identification Navigation Message 50.000 Hz Time of week Ephemeris (Current position) Almanac-Global data
Acquisition Uses C/A code to find satellites Tracking Performs phase lock loop to keep track of satellites
3 satellites solve for X,Y,Z Inaccurate receiver clock. 4 satellites solve for receiver time bias. Sampling frequency Plays role in error.
Process faster than sampling rate. Solution must be accurate within 100m Implies sampling rate greater than or equal to 4Mhz For industry Minimum amount of Ram. Acquisition time will dictate this space. Hardware costs Minimum amount of processing power How fast you clean up Ram Tracking loop efficiency Acquisition algorithm efficiency Dictate battery life & cost of processor.
SoftOSGPS 12-7-2008 It is able to process IF files or real time data from the GPS1A or SiGe with various options for sub sampling and packing of the data. Please read the file READMEFIRST for more detailed instructions. GPS Toolkit GNU LGPL, Signal Tracking Simulation, Ionospheric modeling, Positioning GPS-SDR Uses FPGA board to supply computer with IF frequency. Pervious Project Locates current position once. Takes 4 minutes.
LNA (Low Noise Amp) IF frequency of 4MHz Sampling frequency of 16MHz Performs A/D conversion Outputs 1 byte signed value (-4 to 4) via USB.
Acquisition Created chart of signal correlation strength. Used for future optimizations of acquisition stage. Tracking Performed timing analysis. Implemented optimizations. Structure Designing layout of new structure.
Tracking time (Seconds) Last years code210 Trig metric lookup table126 Decimation 198 Decimation 282 Removed multiplication60 Combined 3 for loops to 129 Switched to release build12 Removed decimation22 Total OptimizationSpeed increase of 10x
TaskRefreshFinish Date Continuous importing of signal data16MHz1/27/09 Continuous deleting of signal data3ms2/10/09 Acquisition from data20 sec2/17/09 Continuous tracking of data1ms3/2/09 Continuous solution update1 sec3/16/09 Develop GUI3/30/09 Optimize Acquisition(Optional)4/13/09 Write final report4/20/09 Prepare final presentation4/27/09 Final Presentation5/5/08
Borre, Kai et.al. Software-Defined Gps and Galileo Receiver. Basel: Birkhhäuser, 2007. Tsui, James. Fundamentals of Global Positioning System Receivers. Hoboken: John Wiley & Sons Inc, 2005. Hurn, Jeff. GPS A Guide to the Next Utility. Wikipedia, Global Positioning System [online], available from World Wide Web:.