Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter

Area of Science:

• Ultrasonic testing
• Signal processing
• Digital filter design

Background:

• Accurate time delay estimation is crucial for ultrasonic phased array focusing.
• Traditional Cascade-Integrator-Comb (CIC) filters face limitations in interpolation and multichannel processing.
• Existing CIC filter designs can exhibit suboptimal passband flatness and transition band steepness.

Purpose of the Study:

• To develop a novel 8x interpolation CIC filter parallel algorithm for improved ultrasonic phased array focusing time delay accuracy.
• To optimize the algorithmic structure for reduced computational complexity and increased processing speed.
• To enhance the performance characteristics of the CIC filter, including passband flatness and stopband attenuation.

Main Methods:

• Proposed an 8x interpolation CIC filter parallel algorithm enabling simultaneous interpolation and multichannel decomposition.
• Derived a general formula for arbitrary multiple interpolation CIC filter parallel algorithms.
• Implemented a compensated CIC filter to improve frequency response characteristics.
• Verified the algorithm's feasibility on a Field Programmable Gate Array (FPGA).

Main Results:

• Reduced computational complexity by 12.5% for additions and 29.2% for multiplications.
• Achieved a time delay accuracy of 1 ns for defect echoes with an 8x interpolation filter at a 125 MHz system clock.
• Demonstrated a flatter passband, steeper transition band, and increased stopband attenuation with the compensated CIC filter.
• Simulation and experimental results confirmed the algorithm's strong feasibility.

Conclusions:

• The proposed 8x interpolation CIC filter parallel algorithm significantly enhances ultrasonic phased array focusing time delay accuracy.
• The algorithm offers fast computation, low computational load, and high resolution, suitable for demanding applications.
• The compensated CIC filter provides superior frequency response characteristics compared to traditional designs.