Ultrasonic Probe Bias Voltage Control for cMUT Sensitivity
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Solution Overview
Problem
Ultrasonic probes using cMUT chips experience sensitivity reduction due to the collapse state, where the center portion of the film body comes into contact with the lower electrode, leading to charge transfer and reduced electromechanical coupling coefficients.
Innovation Solution
An ultrasonic diagnosis apparatus and probe that calculate and manage the bias voltage to prevent the collapse state by measuring and storing the collapse voltage, ensuring the bias voltage supplied to the vibrating elements remains below the collapse voltage, thereby maintaining sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bias voltage is increased to improve ultrasonic transmission, then electromechanical coupling coefficient increases, but sensitivity reduction occurs due to collapse state and charge transfer
Solution Approach 1:
The system performs preliminary measurement of the collapse voltage characteristic for each vibrating element before ultrasonic examination. This advance characterization allows the control unit to determine a safe bias voltage level that prevents collapse state and charge transfer, thereby maintaining sensitivity while still achieving adequate electromechanical coupling for ultrasonic transmission.
Solution Approach 2:
The system dynamically adjusts the bias voltage parameter based on measured collapse voltage characteristics of individual vibrating elements. By changing the bias voltage from a fixed value to a dynamically determined value specific to each element's collapse characteristics, the system optimizes the balance between electromechanical coupling and sensitivity preservation.
2Manufacturing precision
If cMUT chip is used to improve ultrasonic probe performance, then manufacturing precision and electromechanical coupling are enhanced, but collapse state causes sensitivity reduction
Solution Approach 1:
The system incorporates feedback by measuring the collapse voltage of each vibrating element and using this information to control the bias voltage application. This feedback mechanism ensures that the benefits of cMUT manufacturing precision are maintained while preventing the collapse state that would otherwise reduce sensitivity.
Solution Approach 2:
The collapse voltage measurement is performed in advance during probe initialization or calibration, before the actual ultrasonic examination begins. This preliminary characterization of each cMUT element's collapse behavior enables subsequent safe operation that maintains both the manufacturing precision advantages and sensitivity.
3Reliability
If charge transfer is prevented to maintain sensitivity, then electromechanical coupling coefficient is preserved, but bias voltage control complexity increases
Solution Approach 1:
The system performs self-characterization by automatically measuring the collapse voltage of each vibrating element without requiring external intervention or complex manual calibration procedures. This self-service approach simplifies the overall process despite the need for individualized voltage control, as the system generates its own control parameters autonomously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses sensitivity reduction in ultrasonic probes by preventing charge transfer and maintaining optimal electromechanical coupling coefficients, ensuring consistent ultrasonic image quality.
Implementation Method 1
a cMUT chip as disclosed in Patent Document 1 has been recently adopted for the ultrasonic probe. The cMUT chip is an ultrafine capacitance type ultrasonic transducer manufactured by a semiconductor micro-fabrication process
Implementation Method 2
when an applied bias voltage is equal to some voltage, the center portion of a film body of an vibrating element (containing an upper electrode) comes into contact with the surface of a lower electrode, charge transfer from the lower electrode to the upper electrode occurs
Data Source
AI summary
An ultrasonic diagnosis apparatus including an ultrasonic probe having plural vibrating elements whose electromechanical coupling coefficients vary in accordance with the magnitude of a bias voltage supplied from a bias voltage supply unit, an ultrasonic image constructing unit for constructing an ultrasonic image on the basis of a reflection echo signal received from the ultrasonic probe, and a display unit for displaying the ultrasonic image is equipped with a calculation unit for calculating the magnitude of the bias voltage with respect to a collapse voltage of the vibrating elements, a storage unit for storing the calculated magnitude of the bias voltage, and a control unit for making the bias voltage supply unit supply the bias voltage to the vibrating elements in accordance with the stored magnitude of the bias voltage.