Wireless Impedance Spectrometer Multi-Frequency Permittivity
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Solution Overview
Problem
Current noninvasive material testing methods, such as RFID-based systems, cannot independently estimate both the real and imaginary parts of a material's permittivity due to the need for single measurements of signal strength, which limits their ability to provide a full characterization of the material's dielectric properties.
Innovation Solution
A system using a resonant antenna transponder embedded in the material, capable of responding to RF signals at multiple frequencies, allows for the independent calculation of both the real and imaginary parts of the material's permittivity by measuring signal strength at different frequencies, and optionally employs an antenna tuner or multiple non-tunable transponders to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single frequency RF signal is used for material testing, then the measurement process is simple and quick, but both real and imaginary parts of permittivity cannot be independently estimated
Solution Approach 1:
The system transmits RF signals at multiple different frequencies periodically and measures the signal strength at each frequency. By using periodic multi-frequency signaling, the system obtains multiple measurements (real and imaginary parts of permittivity) without requiring complex continuous monitoring, thus resolving the contradiction between measurement speed and characterization completeness.
Solution Approach 2:
The system changes the frequency parameter of the RF signal to obtain different measurements. By varying the frequency parameter across multiple signals, the system extracts different components of permittivity (real and imaginary parts) from the material, enabling complete characterization while maintaining simple single-frequency measurement techniques at each step.
2Measurement precision
If multiple frequencies of RF signals are transmitted to estimate both real and imaginary parts of permittivity, then complete material characterization is achieved, but the measurement process becomes more complex and time-consuming
Solution Approach 1:
The system uses periodic transmission of multiple frequency signals with a simple measurement process at each frequency. The periodic nature allows the system to maintain complexity only in the signal generation (multiple frequencies) while keeping the measurement process simple and repeatable, thus achieving complete characterization without excessive complexity.
Solution Approach 2:
The measurement process is segmented into separate single-frequency measurement steps, where each step estimates either the real or imaginary part of permittivity. This segmentation allows the complex multi-frequency characterization to be broken down into simple, manageable single-frequency measurements, reducing overall process complexity while maintaining completeness.
3Measurement precision
If traditional impedance spectroscopy with parallel plates is used, then accurate permittivity measurement is achieved, but the material must be placed between plates which may damage or alter the material
Solution Approach 1:
The system replaces the mechanical parallel-plate capacitor configuration with a wireless RF signal transmission system. Instead of physically placing the material between plates (which may damage or alter it), the system transmits RF signals through the material and measures signal strength, achieving accurate permittivity measurement without mechanical contact or confinement that could harm the material.
Solution Approach 2:
The system uses RF signals as an intermediary to measure material properties without direct physical contact. The RF signals act as a mediator that interacts with the material's permittivity while allowing remote measurement, thus avoiding the harmful effects of physical plate contact while maintaining measurement accuracy.
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
Enables accurate, noninvasive estimation of both the real and imaginary parts of the material's permittivity, facilitating remote monitoring of material conditions and properties like moisture content or concrete integrity without damaging the material.
Implementation Method 1
A resonant antenna transponder embedded in the material, capable of responding to RF signals at multiple frequencies
Implementation Method 2
The transponder comprises a resonant antenna coupled to the material such that the response of the antenna is affected by the material
Data Source
AI summary
A system and method for measuring the permittivity and/or the impedance of a material are based on transmitting a first RF signal to a transponder coupled to the material. The transponder is equipped with a resonant antenna coupled to the material such that the response of the antenna is affected by the material. The signal strength of a second RF signal transmitted by the transponder in response to the first RF signal, and received by an interrogator, is measured. The interrogator can calculate both the real part and the imaginary part of the complex impedance of the material from multiple measurements of the signal strength of the second RF signal taken at a plurality of frequencies of the first RF signal.