Multi-Level Transmitter Circuit Constant Impedance Output
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Solution Overview
Problem
Multi-level transmitter circuits for capacitive transducers face impedance mismatch issues due to varying output impedances for different voltage input signals, which can be mitigated but at the cost of reduced resolution and penetration when using two-level drivers with proper termination and complex binary codes.
Innovation Solution
A multi-level transmitter circuit design with a capacitive transducer connected between a voltage input and ground, featuring voltage paths controlled by PMOS and NMOS transistors and diodes, including current sources to maintain substantially constant output impedance across different voltage levels, utilizing Schottky diodes for reduced diode drop and faster switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-level transmitter circuit is used to drive capacitive transducers, then the resolution and penetration of the transducer are improved, but the output impedance varies with different voltage input signals causing impedance mismatch
Solution Approach 1:
The patent changes the operating parameters of the transistors by applying different gate voltages to control their conductivity. By adjusting the gate voltages of PMOS and NMOS transistors in different voltage paths, the circuit maintains substantially constant output impedance across multiple voltage levels while preserving high resolution capability
Solution Approach 2:
The patent introduces controlled impedance paths with transistors and diodes as intermediary elements between the voltage sources and the transducer. These intermediary components act as impedance transformers that maintain consistent output impedance regardless of the selected voltage level, thereby resolving the impedance mismatch problem
2Reliability
If a two-level driver with proper termination is used to avoid impedance mismatch, then the impedance matching is improved, but the resolution and penetration of the transducer are reduced
Solution Approach 1:
The patent segments the voltage output into multiple discrete levels (five levels shown in FIG. 1b) while maintaining impedance matching through controlled transistor conductivity. Each voltage level has dedicated transistor paths that are selectively activated, allowing high resolution multi-level operation without the impedance mismatch problems of conventional approaches
3Measurement precision
If different voltage paths with multiple transistors and diodes are used to achieve multi-level output, then the voltage resolution is improved, but the circuit complexity increases
Solution Approach 1:
The patent employs universal transistor and diode components that serve multiple functions: voltage switching, impedance control, and signal routing. The same types of PMOS and NMOS transistors are used in different voltage paths with different gate control voltages, reducing the need for specialized components and simplifying the overall circuit design while maintaining multi-level resolution
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 circuit achieves signal-independent reflection with minimized settled voltage uncertainty and consistent output impedance throughout the range of voltage pulses, enhancing the performance and reliability of the transducer by maintaining low impedance during pulsing and damping operations.
Implementation Method 1
A second voltage path connects the voltage input to a second positive voltage source less than the first positive voltage source through a diode
Data Source
AI summary
A multi-level transmitter circuit with substantially constant output impedance has a capacitive transducer connected between a voltage input and ground. A first voltage path connects the voltage input to a first positive voltage source. The first voltage path is controlled by a first control signal. A second voltage path connects the voltage input to a second positive voltage source, less than the first positive voltage source. The second voltage path passes through a diode and is controlled by a second control signal. A third voltage path connects the voltage input to a third voltage source, less than ground, and is controlled by the second control signal. The impedance at the voltage input during the first control signal is substantially the same as the impedance at the voltage input during the second control signal.