Kristoffer Flores, Shawn Young

1
ACTIVE SONAR TRANSMITTER
Kristoffer Flores, Shawn Young
kbf041000_at_utdallas.edu, scy041000_at_utdallas.edu
Department of Electrical Engineering Erik Jonsson
School of Engineering Computer
Science University of Texas at Dallas Richardson,
Texas 75083-0688, U.S.A.
Project Goals
Project Results

• Design and implement a variable frequency sonar
  transmitter for active ranging
• Involves digital waveform generation with a
  microprocessor, digital-to-analog conversion, and
  signal amplification before outputting to a
  transducer
• Transmitter should be able to receive commands
  from higher AUV processor and be made ready to
  communicate with other AUV systems

• Microprocessor/DAC
• DAC able to output sine wave accurate to within
  3 of desired frequency
• Frequency and number of periods shown are
  variable
• Able to output burst mode sine wave or 4-bit
  Barker code (stream of binary bits) either with
  Binary Phase-Shift Keying or On-Off Keying.
• Receive commands via a serial USART interface

Barker code output - 1011
Project Overview

• Main AUV processor sends a command serially to
  sonar microprocessor to output a signal
• Microprocessor-generated output allows for varied
  waveforms and more precise control of the output
  signal. A sine look-up table and assembly
  language optimization allows for fast and
  accurate signal generation. The microprocessor
  outputs the 8-bit code in parallel to a
  digital-to-analog converter (DAC)
• DAC converts binary output of microprocessor into
  a 2.5 V p-p analog signal

• Power Amplifier
• Push-pull amplifier with enable switch controlled
  by microprocessor
• Amplified burst 2.5 V p-p signal to 80 V p-p at
  40 kHz
• Signal output with BPSK signal highly distorted

• Example Range Accuracy Test of
• Transducer and Hydrophone
• Function generator - 40 kHz
• 20 V p-p burst signal to transducer
• Received signal at hydrophone
• 8 m away
• 70 mV p-p with 5.260 ms delay
• Calculated distance 7.87 m
• (speed of sound in water delay)

Project Conclusions

• Circuit capable of outputting pulses of
  frequencies between
• 2550 kHz
• Maximum output signal at 40 kHz at 80 V p-p
• Testing with hydrophone shows a useable range of
  8 m with a
• 20 V p-p burst signal driving the transducer.
  Calculated distances
• with received signal delay in pool tests were
  within 3 of actual
• distance
• Improve PCB layout
• Explore controlling directionality of output
  pulse
• Integrate sonar transmitter with rest of AUV
  systems

Goals for Next Semester