Passive Wireless Ultrasound Sensor for Extended Reading Distance
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Solution Overview
Problem
Existing MEMS sensor technologies require battery-powered integrated circuits for reading sensor data, limiting their use in passive wireless sensor applications, especially in harsh conditions or where wiring is impractical.
Innovation Solution
A wireless ultrasound sensor system that uses modulated backscattering to read generic MEMS sensor elements without an embedded IC or power source, utilizing an antenna to receive radio frequency signals for energy and transmit data, enabling high frequency and directivity with a low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If passive wireless sensors without battery are used, then operation duration is extended and cost is reduced, but reading distance and data transmission capability are limited
Solution Approach 1:
The patent introduces an intermediary power transfer mechanism using electromagnetic coupling between a reader device and the passive sensor. The reader generates an electromagnetic field that induces current in the sensor's coil, enabling power transfer without direct contact or wired connection. This intermediary field-based power transfer allows the passive sensor to operate at extended distances while maintaining sufficient power for sensing and communication functions.
Solution Approach 2:
The system employs periodic modulation of the electromagnetic field at specific frequencies to enable selective power transfer and data communication. The reader device modulates the electromagnetic field periodically, and the passive sensor responds by modulating its backscattered signal at the same frequency, enabling reliable reading distance extension through frequency-selective periodic interaction.
2Reliability
If RFID sensors are used to extend reading distance, then operation frequency increases, but power consumption increases due to additional sensor elements
Solution Approach 1:
The patent designs a multi-functional passive sensor system where a single integrated structure performs multiple functions: the coil serves as both the power receiving antenna and the data transmission antenna through backscattering, the piezoelectric element functions as both the sensing element and the ultrasonic wave generator, and the housing provides both mechanical support and acoustic isolation. This multi-functionality eliminates the need for separate power management circuits and additional sensor elements, thereby reducing power consumption while maintaining extended reading distance capability.
3Device complexity
If SAW RFID tags are used for sensing, then no external sensor element is needed, but operation frequency is limited by line width of acoustical reflectors
Solution Approach 1:
The patent replaces the SAW-based acoustic wave manipulation mechanism with a direct piezoelectric ultrasonic wave generation mechanism. Instead of using surface acoustic waves propagating on a piezoelectric substrate with acoustical reflectors, the system uses a piezoelectric element directly coupled to a fluid-filled cavity that generates ultrasonic waves at higher frequencies. This mechanical substitution enables operation at ultrasonic frequencies (20 kHz to several MHz) that are not limited by the line width constraints of SAW reflectors.
4Measurement precision
If inductively-coupled electrical resonance-circuit sensors are used, then sensing capability is achieved, but reading distance is limited by near-field coupling requirement
Solution Approach 1:
The patent transitions from near-field inductive coupling in the electromagnetic near-field dimension to far-field electromagnetic radiation in the electromagnetic far-field dimension. The passive sensor is designed to resonate at the reader's electromagnetic frequency, absorbing energy from the reader's electromagnetic field and re-radiating a modulated signal back to the reader. This dimensional transition from near-field coupling to far-field radiation enables extended reading distance while maintaining sensing capability through frequency-selective resonance.
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
This solution allows for longer reading distances, reduced power consumption, cost efficiency, and the ability to operate in multiple frequency bands, making it suitable for medical, industrial, and well-being applications, including implantable sensors without the need for batteries.
Implementation Method 1
antenna means for receiving radio frequency signals... The radio frequency signals provide energy for driving the ultrasound transmitter
Implementation Method 2
ultrasound transmitter having a cavity adjusted in connection with it... ultrasound transmitter comprising a light structured membrane vibrator/oscillator
Implementation Method 3
cavity adjusted in connection with it... resonance criteria is completed with the frequency used... measures the frequency alteration
Data Source
AI summary
The invention relates to a sensor and a system for measuring pressure, variation in sound pressure, a magnetic field, acceleration, vibration, or the composition of a gas. The sensor comprises an ultrasound transmitter, a cavity, and a passive sensor element. In accordance with the invention the sensor includes antenna means for receiving radio frequency signals (f1, f2), and connecting means connecting the antenna to the ultrasound transmitter for using the radio frequency signals for providing energy for driving the ultrasound transmitter.