EJAE GPS Receiver

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EJAE GPS Receiver
Senior Design I
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The Team
Cord ReynoldsTeam Leader
Robbie Holt
Dr. Rose HuAdvisor
Brian Barnes
Jason Pacher
Matt McNeece Tech. Advisor
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Teams Tasks
Research Design Document Website MS Project Software Hardware Testing
Cord Reynolds x x x x x
Brian Barnes x x x x
Robbie Holt x x x x
Jason Pacher x x x x x
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Why Is EJAE Receiver Needed

• Lost in the woods.
• Able to relay position to emergency rescuers if
  stranded in a barren location.
• Used to find the distance from your location to a
  location on a map.
• Hurricanes
• Favorite fishing location

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How GPS Works

• Acquire 4 satellite signals.
• Convert an analog signal to a digital signal.
• Calculate digital signal into the coordinates of
  the user.
• Display the user location onto a screen.

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Competitive Analysis

• Present different competing GPS receivers and
  their features
• Show EJAE Receivers benefits over competitors

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Design Constraints

• Accuracy
• Position accurate to within 15 meters 99 of the
  time.
• Power Consumption
• Consumes no more than 5 watts of power.
• Initial Position Calculation Time
• Displays a user position within 4 minutes.
• LCD Updating Frequency
• Position will be updated every 10 seconds.

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Practical Use

• Safety
• The unit casing and wiring will be designed as to
  prevent electric shock to the user.
• Cost
• Price will be under 100.
• Usability
• Receiver will only have an ON/OFF switch.

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Practical Use (Cont.)

• Reliability
• This system will be designed to operate over a
  five year period without failure.
• The expected battery life is 3.5 hours and is the
  only part requiring regular maintenance.
• Size and Weight
• The physical dimensions will be 1.5 high, 3
  wide, 4 long and weigh less than 12 ounces.

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Physical Model
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Interior Design ModelAcquisition

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Interior Design ModelTracking

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Interior Design ModelConverting
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Functions Used

• correlcontrol()
• deccorrel()
• userposition()
• gdop()

• satposition()
• lcdoutput()
• atmdelay()

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Software Ctrl Flow-Chart
Processor
Sat/PRange
C Ctrl
Correlator
GDOP
Decode
User Pos.
Atm Delay
LCD out
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Correlator Ctrl Algorithm

• Software to communicate with correlator registers
  to acquire and track satellite
• Pick Gold Code or PRN to search for.
• Set the signal from the FE to 1.4 MHz so that it
  will stay in phase with the satellite signal for
  adequate time
• Start the correlation process and obtain the data
• Decide if GPS signal is found
• Start process over or continue

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Decode Correlator

• Process pseudo-ranges which will eventually give
  the user position
• Read in accumulate and measurement
  data-gtpseudo-range
• Pseudo-range data into ephemeris data

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Decode Correlator cont.

• Ephemeris data into separate variables
  deccorrel()
• Atmospheric refraction correction atmdelay()
• Calculate satellite position satposition()

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Sat/Prange LCD out

• Have coord. in x,y,z.now what??
• Choose best satellites. gdop()
• We will use geometric dilution of precision
• Choose satellites farthest apart
• Calculate user position userposition()
• Communicate to the LCD to display user position
  lcdoutput()

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User Position

• Step through how userposition() works
• Equations
• Assumptions

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Design Issues

• Error Margin
• Low enough to produce an accurate answer
• High enough not cause algorithm to take too long
  to compute

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Simulations
Func Name Internal Error Avg. Run Time (s)
userposition() .01 .06
gdop() 10 .05
satposition() 10 .002
lcdoutput() 0 3
atmdelay() 10 .008
deccorrel() 0 15

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Demonstration

• Hopefully!!

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Estimated Cost
Part Cost
Antenna 2.43
RF Front End 9.40
Correlator 16.45
Processor 9.38
LCD Display 3.62
Filters, Crystals 1.50
Resistors, Capacitors, Inductors 3.33
Total Cost 46.15
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Future Work

• Reduce calculation time
• Improve Accuracy of the EJAE Receiver
• Possible modifications
• Backlit LCD Screen
• Less Battery Usage

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Acknowledgements

• God
• Dr. Hu
• Dr. Picone
• Jordan Goulder