Sonar Imaging System

EEE3097S DESIGN

The aim of this project is to design, build and test an imaging sonar operating at 40 kHz in air.

This project split into milestones

1. Create Documentation for user requirements, design calculations, sequence diagrams, activity diagrams, etc.
2. Simulate a 1-D chirp pulse transmission and reception
3. Build and test 1-D sonar
4. Simulate 2-D sonar with fan beam image
5. Build and test 2-D sonar imaging sysem.

File Descriptions:

• chirp_gen.ipynb used to generate array of values in chirp (int values pre-adjusted for DAC)
• globals.h contains chirp array
• Chirp_Output.ino produces chirp using teensy 3.6 DAC0.
• LibSerialPort.ipynb to receive buffer from Teensy through serial port
• Sampling.ino samples using ADC on teensy.

1D imaging Sonar:

one transmitter and one receiving transducer.

2D imaging sonar:

requires that a narrow beam is steered over a range of angles to form a fan-beam image. Steering can be implemented electronically by using a linear array of transducers, either for the transmitter beam or the receiver beam. By combining the received signals with appropriate delays, beam steering can be achieved.

3D imaging sonar:

can be implemented in different ways. A simple method is to use two perpendicular arrays, one for steering a transmit beam, and the other for steering a receive beam. This achieves 3D imaging with a minimum number of channels (compared to a conventional NxN receiving array).

Some Theory

Simple 1D pulse-echo sonar

Matched filtering of received signal

Radar/sonar transmits a chirp pulse (wide bandwidth for fine resolution; long in duration for high energy. Received signal is passed through a matched filter. Output waveform has improved peak SNR. Below is shown a simulation of one echo.

2D/3D Sonar Imaging System operating at 40 kHz

Received Waveforms on oscilloscope when testing 1-D sonar