Transducer Interface Impedance Matching for Accurate Time-of-Flight
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ultrasonic transducers face accuracy issues when their impedance characteristics change due to configuration interchange, leading to degraded signal quality and measurement inaccuracies, particularly due to temperature fluctuations and aging.
Innovation Solution
The implementation of a self-calibrating system that matches the impedances of output transistors between different configurations of ultrasonic drivers using programmable-finger transistors, allowing for iterative measurement and programming to adjust drive strengths and ensure reciprocity between transmitter and receiver roles, thereby compensating for impedance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transducers are configured to operate as both transmitters and receivers, then versatility is improved, but measurement precision deteriorates due to impedance variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the impedance characteristics of output transistors through programmable-finger transistor arrays. The system measures impedance in one configuration and programs complementary metal-oxide-semiconductor (CMOS) circuits to compensate for impedance differences when switching between transmitter and receiver modes, thereby maintaining measurement precision across configuration changes.
2Productivity
If transducers operate over extended periods, then productivity is improved, but reliability deteriorates due to aging effects on impedance characteristics
Solution Approach 1:
The patent implements feedback by continuously measuring the impedance of output transistors during operation and using these measurements to program compensating impedance values in CMOS circuits. This closed-loop feedback mechanism counteracts aging effects and maintains reliable operation over extended periods by dynamically adjusting transistor finger configurations based on real-time impedance measurements.
3Measurement precision
If impedance matching is performed through programmable-finger transistors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the output transistor structure into multiple programmable-finger segments. Each finger can be independently controlled through CMOS switching circuits, allowing precise impedance matching by selectively enabling or disabling individual fingers. This segmented approach provides fine-grained control over impedance characteristics while using standard CMOS fabrication processes.
Data Source
AI summary
In described examples, a first and second driver each include a first-rail output transistor including a first terminal coupled to a first power rail and a second-rail output transistor including a first terminal coupled to a second power rail. The first-rail output transistor of each of the first and second drivers includes a second terminal coupled to a second terminal of the second-rail output transistor of an output node of each respective first and second driver. A resistive load includes a first terminal coupled to the first-driver output node and includes a second terminal coupled to the second-driver output node. A sampling circuit generates an indication of an impedance of at least one of the output transistors of the first and second drivers.