Phase-Coded Modulation-Based Time-of-Flight Measurement Improvement for Piezoelectric Ceramic Transducers

Area of Science:

• Acoustics
• Signal Processing
• Metrology

Background:

• Ultrasonic time-of-flight (ToF) measurement is crucial in various applications.
• Low-bandwidth (40 kHz) ultrasonic transducers often suffer from inaccurate ToF measurements using traditional threshold detection.
• Limited transducer bandwidth poses challenges for precise distance sensing.

Purpose of the Study:

• To improve the accuracy and stability of ToF measurements with low-bandwidth ultrasonic transducers.
• To introduce and evaluate advanced correlation-based methods for ToF sensing.
• To compare the performance of novel coding techniques against standard threshold detection.

Main Methods:

• Proposed a variant of the correlation method for ToF measurement.
• Utilized Barker 13 and derived codes, along with code band narrowing techniques.
• Conducted experimental evaluations with 1000 measurements per code and modulation scheme.
• Selected sample standard deviation (SSD) as the primary metric for stability assessment.

Main Results:

• The proposed correlation method significantly enhanced ToF measurement accuracy and stability.
• Quadriphase codes and codes with fluent phase change demonstrated superior performance.
• Achieved SSD values less than 20% of threshold detection SSD across all tested codes.
• In best cases, SSD was reduced to less than 10% of the threshold detection method's SSD.

Conclusions:

• Correlation-based methods, particularly with quadriphase and fluent phase change codes, offer substantial improvements for ToF measurements using low-bandwidth transducers.
• The developed techniques provide more stable and accurate distance sensing compared to conventional threshold detection.
• This research contributes to more reliable ultrasonic sensing applications by addressing bandwidth limitations.