Microwave Cantilever Resonator for Weak AC Magnetic Field Sensing
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Solution Overview
Problem
Existing microwave resonator magnetic field measuring devices face challenges in measuring weak alternating magnetic fields due to interference from thermal noise of the piezoelectric layer and complexity in manufacturing, with a need for miniaturization and improved sensitivity.
Innovation Solution
A magnetic field measuring device using a microwave resonator with a cantilever and magnetostrictive layer, eliminating the piezoelectric element and utilizing two independent resonances to enhance sensitivity, where the magnetostrictive phase is part of a detunable microwave resonator, allowing for frequency changes with magnetic field measurement, and readout via high-frequency microwaves to eliminate thermal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric layer is used to convert mechanical deflection into an electrical measurement signal, then the sensor can measure magnetic fields, but thermal noise from the piezoelectric layer interferes with measuring weak magnetic fields
Solution Approach 1:
The patent removes the piezoelectric layer from the sensor structure entirely, extracting the source of thermal noise interference. Instead of using piezoelectric materials to convert mechanical deflection to electrical signals, the invention employs direct optical detection methods that eliminate this harmful thermal noise source, thereby improving the ability to measure weak magnetic fields.
Solution Approach 2:
The patent replaces the piezoelectric conversion mechanism with an optical detection system. Rather than relying on piezoelectric materials to generate electrical signals from mechanical deflection, the invention uses optical methods to detect the mechanical deflection caused by magnetostrictive effects, substituting a mechanical-electrical conversion system with a mechanical-optical detection system that avoids thermal noise interference.
2Measurement precision
If conventional magnetoelectric sensors are used with piezoelectric layers, then magnetic field measurement is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and removes the piezoelectric layer from the sensor structure, simplifying the manufacturing process. By eliminating this complex component and its associated fabrication steps, the invention reduces manufacturing complexity while maintaining magnetic field measurement capability through alternative magneto-optical mechanisms.
Solution Approach 2:
The patent employs composite material structures that integrate magnetostrictive materials with optical detection components, replacing the traditional piezoelectric composite structure. This alternative composite approach simplifies manufacturing by using materials and assembly processes that are more compatible with existing fabrication techniques while achieving the same measurement function.
3Volume of moving object
If the sensor structure is miniaturized for compact applications, then device size is reduced, but sensitivity to weak magnetic fields decreases
Solution Approach 1:
The patent replaces the piezoelectric-based mechanical-electrical conversion system with an optical detection system that is inherently more sensitive and scalable to miniaturization. The optical detection method maintains high sensitivity even in miniaturized configurations because it directly detects mechanical deflection without the noise floor imposed by piezoelectric thermal noise, enabling compact sensors to retain weak field detection capability.
Solution Approach 2:
The patent utilizes mechanical vibration and resonance phenomena in the magnetostrictive layer to amplify the response to weak magnetic fields. By operating at resonant frequencies, the sensor structure enhances its sensitivity to small magnetic field variations even when miniaturized, as the resonant amplification compensates for the reduced size and maintains detection capability for weak fields.
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 approach simplifies manufacturing, reduces noise interference, and enables more precise measurement of weak magnetic fields by using high-frequency resonances, allowing for miniaturization and remote readout without external power or connections, suitable for applications like biomagnetic signal detection.
Implementation Method 1
conventional ME sensors convert an alternating magnetic field into a change in length via a magnetostrictive material
Implementation Method 2
the mechanical deflection caused by the change in length is detected optically, for example by means of a laser
Implementation Method 3
If a microwave with a frequency in the vicinity of the ferromagnetic resonance, hereinafter also called FMR, is applied, it is coupled into the applied substrate and partially absorbed or transmitted in the FMR
Implementation Method 4
which causes a change in polarization and thus a terminal voltage as a measurement signal in a piezoelectric layer
Data Source
AI summary
A microwave resonator magnetic field measuring device (1) for measuring alternating magnetic fields, with a base plate (11) having at least one supporting/bearing/clamping point (111), at least one mechanical oscillator (12+13) formed as a microwave resonator in the form of a cantilever (13) having at least one magnetostrictive layer (12), the latter being connected and mounted at at least one point to the base plate (11) in the at least one supporting/bearing/clamping point (111), at least one input coupling means (161) for microwaves and at least one output coupling means (162) for microwaves, wherein the base plate (11) and the mechanical oscillator (12+13) formed as a microwave resonator are at least partly electrically conductive and electrically conductively connected to one another. Also, a magnetic field measuring method having a magnetic field measuring device according to the invention.