Coupled-Mode Transponder With Variable Load for Compact Sensing
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Solution Overview
Problem
Existing remotely interrogatable passive transponders face challenges in producing delicate devices with precise dimensions for electromechanical coupling, which are prone to temperature drifts and require large dimensions for suitable delays, making them unsuitable for small-scale applications and frequency versatility.
Innovation Solution
A transponder design featuring coupled resonators with evanescent wave coupling, allowing for mode coupling conditions through a narrow zone, where the second resonator is connected to a variable load element, enabling reliable ON/OFF mode identification and differential frequency measurement, and utilizing materials like quartz or lithium niobate to mitigate temperature effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If delay lines are produced on lithium niobate with precise electrode dimensions for electromechanical coupling, then the electromechanical coupling coefficient is improved (Ks2 ≥ 5%), but the device exhibits large temperature drifts and requires large dimensions (6-10 mm)
Solution Approach 1:
The patent changes the operating parameters by using coupled resonant modes instead of traditional delay lines, operating at different frequency bands (434 MHz, 866 MHz, 2.45 GHz) with adjusted resonator dimensions and coupling coefficients to achieve compact sizes while maintaining reliability
Solution Approach 2:
The delay line structure is segmented into multiple resonators (first resonator and second resonator) with distinct functions - one for interrogation and one for sensing with variable load, allowing independent optimization of each segment's dimensions and properties
2Length of stationary object
If delay line dimensions are reduced for small-scale applications, then the device size is improved, but the suitable delay performance and bandwidth compatibility are worsened
Solution Approach 1:
The patent introduces dynamic tuning capability through variable load elements (varactors, PIN diodes) that allow the resonant frequency and coupling conditions to be dynamically adjusted, enabling the compact transponder to adapt to different frequency bands and bandwidth requirements
Solution Approach 2:
The transponder design achieves multi-functionality by incorporating variable load elements that enable operation across multiple frequency bands (434 MHz, 866 MHz, 2.45 GHz) and different application modes (reflection, transmission) within a single compact device structure
3Measurement precision
If two independent resonators are used with one modulated by a load, then the sensing capability is improved, but the implementation becomes tricky as the load influences both resonators making reference measurement difficult
Solution Approach 1:
The patent extracts the sensing function to a dedicated second resonator that is selectively coupled to the variable load, while the first resonator serves as a stable reference for interrogation, separating the measurement and reference functions into distinct physical components
Solution Approach 2:
The patent introduces an evanescent wave coupling zone as an intermediary mechanism between the two resonators, allowing energy and information transfer while maintaining electrical isolation, so the load on the second resonator does not directly influence the first resonator's reference signal
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 enables compact, reliable, and self-referenced transponders that operate across various frequency bands, including low ISM bands, with improved sensitivity and reduced temperature drifts, offering frequency versatility and accurate differential frequency measurements.
Implementation Method 1
said first resonator and second resonator(s) being coupled by a narrow zone within which the overlapping of evanescent waves of the fields emitted by the first resonator and second resonator(s) can be established, thus creating mode coupling conditions
Implementation Method 2
said second resonator or resonators are connected via at least one second port, to at least one variable load element (ECV) capable of modifying the coupling conditions of the resonant modes
Implementation Method 3
comprising a piezoelectric material inserted between two first electrodes situated in one and the same plane, and a second electrode
Implementation Method 4
a first transducer positioned between a first reflector and a central reflector, a second transducer positioned between said central reflector and a second reflector
Implementation Method 5
exhibiting at least one first resonant mode and one second resonant mode
Data Source
AI summary
A transponder including a first resonator and a series of one or more second resonators with coupling of evanescent waves exhibiting at least one first resonant mode and one second resonant mode, said first resonator being connected via a first port, to a first means allowing an interrogation, wherein said second resonators are connected via at least one second port, to at least one variable load element capable of modifying coupling conditions of the resonant modes and consequently a response measured on said first port.