Broadband Impedance Matching for Immersed CMUTs: An End-to-End Design-to-Measurement Validation Framework

Area of Science:

• Materials Science
• Acoustics Engineering
• Biomedical Engineering

Background:

• Capacitive micromachined ultrasonic transducers (CMUTs) offer advantages over piezoelectric transducers but face limitations in driving voltage and acoustic power, especially polymer-based CMUTs.
• Enhancing acoustic power output is crucial for the clinical and practical deployment of CMUT arrays in medical applications.

Purpose of the Study:

• To present a measurement-driven experimental validation strategy for designing passive broadband impedance-matching networks for immersed polymer CMUT arrays.
• To enhance transmitted acoustic power while preserving operational bandwidth and validate the design framework through experimental measurements.

Main Methods:

• Synthesized matching topologies near the Bode-Fano limit and quantified robustness using Monte Carlo analysis with component variations.
• Implemented and experimentally validated matching networks under unipolar pulse excitation.
• Characterized far-field acoustic pressure in time and frequency domains, comparing results with numerical predictions.

Main Results:

• The optimized impedance matching increased transmit power by a factor of 2.1.
• This enhancement came at the cost of a 40% fractional-bandwidth reduction.
• Experimental validation confirmed the effectiveness of the impedance-matching framework.

Conclusions:

• Established a directly applicable, validated framework for broadband impedance matching in polymer CMUT arrays.
• The developed strategy supports the use of CMUTs as a cost-effective solution for ultrasound imaging and therapeutic systems.
• Demonstrated a practical approach to overcome power output limitations in CMUT technology.