1. Submarine Sonar Detection
Wura Bamgbose, Brian Fletcher,
Ryan LaFrance, Erin Walters
School of ECE
Georgia Institute of Technology
ECE4007 L01
April 20, 2009

2. Project Overview Sonar detection system Marine Robotics Group
Navy competition
Using Mostly pre-existing samples

3. Navy Competition 2009 Bridge Rooftop Rooftop Practice Side
Competition Side
Launch Platform

4. Technical Objectives Amplify and detect a ping between 20-30 kHz
Determine the direction of origin of the ping
Communicate time delay with submarine’s main control system

5. Detect Ping 2s
1.3ms
Frequency: 20-30kHz

6. Measure Time Delay
Pinger t2 t1
t1<t2

7. Adjust Direction
Pinger t2 t1
t1 = t2

8. Physical Constraints Length 5” Width Depth 2” Voltage 24VDC Current 2A
Pic of BOX & mcu 6”
5.5”

9. Sonar System Block Diagram
Variable Gain Amplifier
MCU
Hydrophones
ADC
Pinger
RS232
Measure Time Delay

10. Variable Gain Amplifier
Amplifiers
Variable Gain Amplifier
MCU
Hydrophones
ADC
Pinger
RS232
Measure Time Delay

11. LMC6484IN-ND
Rail-to-Rail Output Swing (within 20 mV of supply rail 100 kW load)
Excellent CMRR and PSRR: 82 dB
Input impedance of 1 TΩ
Quad operational amplifier 11

12. Amplifier Design Performance
Target gain of 100dB
Three stage amplifier circuit
Low gain first stage to limit noise of the signal
Actual gain of 84dB

13. Amplifier Output With 50uV Input

14. Amplifier Output With 500uV Input

15. Amplifier Schematic High-pass filter Low-pass filter
Digital potentiometer

16. Band-pass Filter Target -3dB frequencies of 18kHz & 42kHz
Actual -3dB frequencies of 18kHz & 52kHz 16

17. Variable Gain Amplifier
Microcontroller
Variable Gain Amplifier
MCU
Hydrophones
ADC
Pinger
RS232
Measure Time Delay

18. Sonar System Controller
ADC
RS232
MCU
Measure Time Delay
Samples at 1 Msps
Determines time delay in samples 18

19. Determining Time Delay
Peak detection of signals on both channels
End detection of both signals
Cross correlation between start and end points
Cross correlation has a max at the time delay

20. Signal Detection

21. Cross-correlation V V2 21

22. Auto-calibration Eliminates error from submarine design changes. t1 t2
t1 > t2  t1 = t2
Eliminates error from submarine design changes.

23. Demonstration
Electronics
Laptop
Pool
Serial Cable
Hydrophones
Pinger

24. Remaining Tasks Move cross-correlation code to MCU
Design auto-calibration function
Troubleshoot automatic gain control
Test system in a pool 24

25. Overall Analysis Done well: Improvements: Good noise filtering
High gain
Sufficient sampling rate
Improvements:
MCU with more memory
Build circuit on one PCB to improve performance and reduce size