Team #1: RAPTR
(Remote Asset and Person Tracking Reporter)
Derek Kozel
Andrew Hillenius
Chris Perrone
Allan Wang
4/29/2012
Team Members
Andrew Hillenius
Allan Wang
ahilleni@andrew.cmu.edu
allanw@cmu.edu
Chris Perrone
Derek Kozel
cfperron@andrew.cmu.edu dkozel@andrew.cmu.edu
http://www.ece.cmu.edu/~ece549/spring12/team1/
Concept
• To create a multi-purpose tracking device with many
possible applications.
• A frequency-flexible transmitter, GPS module and high-
capacity battery are combined to create a portable and
tightly-integrated device.
Goals
• Frequency-agile transmitter
• High GPS accuracy
• Long battery life
• Tightly integrated package
• Computer programmable
• Charging over USB
• Permit local data logging
Architecture
Flash Memory
UART, location
data
SPI
Store and Read Data
GPS Module
USB
UART
Configuration,
Data read
500 mA
Battery
Charger
AVR
Wake-up
Interrupt
Accelerometer
Proprietary
Location
Packet
RF Transmitter
16 Mbit
Flash
ATmega324
microcontroller
Temperature
compensated
oscillator
FSK
Transmitter
RF Power Amp
Module
Sleep button
DAC
RF biasing
FT232
USB→UART
Data retrieval and
programming
SMA
VHF antenna
LiPo Charger
14-bit
accelerometer
SMA
GPS antenna
Boost
converter
3.7V -> 8V
3.7V Battery
Connector
GPS module
High-altitude
capable
Experiments
• GPS accuracy over time for hot fix
• Test how accurate the GPS is immediately after reacquiring
location data
• Power consumption
• Used to extrapolate battery life
• Long battery life allows for increased transmit rate
• RF transient spectrum analysis
• Presence of transients and spurious signals determine FCC
certification
Experimental Results: GPS Accuracy
Turned GPS off for 10 seconds
Measured time to achieve a
certain accuracy (10m, 4m, 2m)
GPS Accuracy over time, Hot Fix
20
18
25
Time to achieve accuracy (s)
16
Accuracy (m)
14
12
10
8
6
4
2
20
15
10
5
0
0
0
5
10
15
Time since power on (s)
20
10m
4m
2m
Accuracy (meters)
Experimental Results: Battery Life
Mode
Current
Standby
0.35 mA
Active, GPS
50 mA
Active, Transmitting
850 mA
Extrapolated based on:
• 2200 mAh battery
• GPS hot fix time: 2 – 10 seconds
(depending on last GPS fix time)
• Transmits for 0.4 seconds
Extrapolated Battery Life
Battery Life (Days)
1000
100
10
1
0.1
1
10
100
1000
Minutes between location transmission
Transmission
Interval
Battery Life
30 seconds
6 days
2 minutes
3 weeks
10 minutes
2.5 months
1 hour
5 months
Experimental Results: RF Analysis
• 2.5Watt output power
• Free of transients and spurious signals
Insights from Measurements
• GPS accuracy over time determines battery life
• Allows us to pick how long to wait before deciding reported GPS
data is accurate enough
• Long battery life opens the door for other applications
• Fast beacon rate
• High-resolution package tracking
• Use in emergency situations where power is unavailable
• RF signal free of transients and spurious signals
• Possible candidate for FCC certification
• Responsible use of RF spectrum
• Will not interfere with other radio services
Performance
• Range
• Varies with terrain and receive hardware
• Furthest non-repeated beacon: 13.8 miles
• Power Consumption
• Auto power-off with wake-on-motion.
• Multi-month standby time
Other Features
• Compatibility with worldwide APRS network
• Repeated signals can travel hundreds of miles
• Almost all traffic is reported in public database
• Server software
• For receiving and decoding beacons.
• Used to track moving and stationary objects
• High resolution accelerometer data
• 14-bit accelerometer
• High resolution position beacon
• Increased transmit time but increased accuracy
• Auto power-off and wake-on-motion
• Controlled by accelerometer
Open Issues
• Increased output power
• Device not currently operating at full output power
• Custom packet protocol
• Creating our own protocol would allow for short transmit time while
still achieving high-resolution location information
• Could be integrated into the private server for custom applications.
• Sine wave-based modulation technique
• Improve overall range and weak-signal performance
• Further improve spectral purity
• Increases compatibility
Conclusions
• We learned how to integrate devices with the APRS
network
• What would we have done differently:
• Worked earlier on embedded software
• Use monolithic amplifier from the beginning