Millimeter Wave Sensor for Dielectric Thickness Measurement
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Solution Overview
Problem
Current millimeter-wave and terahertz sensing methods face challenges in accurately measuring the electric length of objects and materials, particularly in non-destructive inspection of thin sheet-like dielectric materials, due to limitations in phase value reliability and surface measurement biases.
Innovation Solution
A method and device utilizing millimeter or terahertz waves with a shared frequency reference for up and down conversion, enabling precise estimation of electric length by converting received signals into in-phase and quadrature components, and using a calibration step to minimize measurement drift, allowing for non-invasive characterization of objects and materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single antenna is used to generate and receive reflected signals, then the device complexity is reduced, but the measurement precision deteriorates due to surface reflection biases and unreliable phase values
Solution Approach 1:
The single antenna system is segmented into separate transmitting and receiving antennas. This allows the transmitted and received signals to be independently optimized and processed, eliminating the surface reflection bias that occurs when a single antenna handles both functions. The separation enables more reliable phase value extraction for thickness measurement.
Solution Approach 2:
A shared frequency reference acts as an intermediary between the transmitting and receiving signal processing chains. This intermediary ensures that both signal paths are synchronized to the same frequency standard, eliminating frequency drift and phase instability that would otherwise degrade measurement precision.
2Reliability
If millimeter-wave and terahertz signals are used for sensing, then the reliability of non-ionizing radiation is improved, but the measurement precision of electric length deteriorates due to phase value unreliability
Solution Approach 1:
A feedback mechanism is implemented where the received signal is mixed with a down-converted version of the transmitted signal. This feedback process allows for continuous monitoring and correction of phase values, ensuring reliable electric length measurements despite the challenges of millimeter-wave and terahertz signal propagation.
Solution Approach 2:
The mechanical challenge of maintaining phase stability at millimeter-wave frequencies is replaced by an electronic solution using shared frequency references and signal mixing. This substitution of electronic control for mechanical stability ensures reliable measurements without requiring extremely precise physical alignment and positioning.
3Measurement precision
If nuclear radiation methods are used for sensing, then the measurement precision of thickness and weight is improved, but the harmful factors to objects and environment worsen due to ionizing radiation
Solution Approach 1:
The sensing parameter is changed from ionizing radiation (nuclear methods) to non-ionizing millimeter-wave and terahertz radiation. This parameter change maintains the ability to measure thickness and weight with high precision while eliminating the harmful effects of ionizing radiation on materials and the environment.
Solution Approach 2:
The potentially harmful high-energy radiation is converted into beneficial non-ionizing radiation. The millimeter-wave and terahertz signals, which would otherwise be considered lower energy and less penetrating, are shown to provide sufficient measurement precision for industrial applications without the harmful effects of ionizing radiation, effectively converting a perceived limitation into an advantage.
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 provides accurate and reliable sensing of physical dimensions, thickness, and weight of materials, enabling topographical mapping and inline inspection with high precision, compliance with safety regulations, and robustness against environmental conditions.
Implementation Method 1
a transmitting signal is mixed with a frequency reference, resulting in a signal comprising at least two tones
Implementation Method 2
a received signal is mixed with a frequency reference, resulting in that the transmitting signal is generated and the received signal is processed by the same frequency reference
Data Source
Figure 1A~1B
Figure 2~3(c)
Figure 4~5
AI summary
The present invention relates to a millimeter or terahertz wave sensor for providing inline inspection, preferably including but not limited to continuous monitoring of objects, for example thin sheet dielectric material.