By: Sam Price Advisor: Dr. In Soo Ahn Overview of GPS Overview of Receivers Current Projects Patents Datasheet Preliminary work Schedule of tasks L1 Carrier wave 1575.420 MHz C/A code 1.023MHz Satellite Identification Navigation Message 50.000 Hz Time of week Ephemeris (Current position) Almanac-Global data Tracking Position Startup Acquisition Loop Calculation 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. Patent Number Description 20060074554 Software-defined GPS receivers and distributed positioning system 20067046193 Software GPS based integrated navigation 20067002515 GPS receiver using software correlation for acquisition and hardware correlation for tracking 2007213932 Computer Programmed with GPS Signal Processing Programs 2005162313 GPS Receiver (Software) •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. CA(t) Nav(t) Cos(IF) Cos(IF) Cos(IF) ½Cos(IF+IF) + ½Cos(IF-IF) ½Cos (2IF) + ½Cos(0) = ½ CA(t)Nav(t) CA(t) XOR CA(t) XOR Nav(t) = Nav(t) 0 XOR Nav(t) = Nav(t) C/A code aligned. C/A code not aligned. Tracking time (Seconds) Last years code 210 Trig metric lookup table 126 Decimation 1 98 Decimation 2 82 Removed multiplication 60 Combined 3 for loops to 1 29 Switched to release build 12 Removed decimation 22 Total Optimization Speed increase of 10x Task Refresh Finish Date Continuous importing of signal data 16MHz 1/27/09 Continuous deleting of signal data 3ms 2/10/09 Acquisition from data 20 sec 2/17/09 Continuous tracking of data 1ms 3/2/09 Continuous solution update 1 sec 3/16/09 Develop GUI 3/30/09 Optimize Acquisition(Optional) 4/13/09 Write final report 4/20/09 Prepare final presentation 4/27/09 Final Presentation 5/5/08 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: <http://en.wikipedia.org/wiki/Global_Positioning- _System>. ?