Practical spread spectrum pulse compression for ultrasonic tissue imaging.

Area of Science:

• Signal Processing
• Ultrasonic Imaging
• Biomedical Engineering

Background:

• Spread spectrum pulse compression enhances critical system performance.
• Ultrasonic imaging requires improved signal-to-noise ratio and dynamic range.

Purpose of the Study:

• To design and construct a digital, real-time, Barker coded, bi-phase modulator for ultrasonic pulse compression.
• To evaluate the performance of spread spectrum pulse compression in an ultrasonic test tank.

Main Methods:

• A digital, real-time, Barker coded, bi-phase modulator was designed and built.
• An ultrasonic test tank with synthetic targets and goat liver was used.
• Cross-correlation with a sidelobe suppression filter was performed on received echoes.

Main Results:

• A 13-bit Barker code compression achieved an 11 dB increase in signal-to-noise ratio.
• Over 30 dB of instantaneous dynamic range was maintained.
• Practical limitations necessitate short code lengths for ultrasonic pulse compression.

Conclusions:

• Spread spectrum pulse compression is effective for enhancing ultrasonic imaging performance.
• The developed system achieved significant improvements in signal-to-noise ratio and dynamic range.
• Further research may explore longer code lengths or alternative compression techniques.