Shielded RFID Strap Bridge Conductor Capacitance
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Solution Overview
Problem
Current RFID tag designs face challenges in achieving resonance within a small area, requiring a combination of chip capacitance and inductance that leads to increased manufacturing tolerances and energy loss.
Innovation Solution
The method involves using shielded RFID straps with a bridge conductor that couples the antenna and strap pads, increasing the total capacitance and reducing the required inductance to resonate at the desired frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resonant element is formed using chip capacitance and inductor to achieve resonance at desired frequency, then the RFID tag can operate at the target frequency, but the inductor occupies significant area and requires tight manufacturing tolerances
Solution Approach 1:
The patent combines multiple capacitance sources (chip capacitance, strap capacitance, and bridge conductor capacitance) to create a total capacitance that resonates with the inductor. This merging of capacitance elements allows the system to achieve the desired resonance frequency while reducing the inductor area requirement, since capacitance and inductance are inversely related in the resonance frequency formula.
Solution Approach 2:
The patent changes the capacitance parameter by introducing a bridge conductor that adds additional capacitance to the system. By increasing the total capacitance value, the required inductance value for resonance is reduced, which directly reduces the inductor area while maintaining accurate resonance frequency operation.
2Area of stationary object
If the inductor is made smaller to reduce area, then the area occupied is reduced, but manufacturing tolerances become tighter and energy loss increases
Solution Approach 1:
By combining multiple capacitance sources (chip, strap, and bridge conductor), the patent reduces the burden on the inductor to achieve resonance. This allows the inductor to be smaller in area while maintaining relaxed manufacturing tolerances, because the additional capacitance compensates for variations in inductor parameters.
Solution Approach 2:
The patent changes the capacitance parameter by adding a bridge conductor, which increases total capacitance and reduces the required inductance. This parameter change allows for a smaller inductor with wider tolerances, as the system has more degrees of freedom to accommodate manufacturing variations.
3Area of stationary object
If the conductor is made narrower to fit in small area, then area is reduced, but resistance increases leading to higher energy loss
Solution Approach 1:
The patent merges multiple capacitance elements to increase total capacitance, which reduces the required inductance and allows for a larger conductor cross-section. This wider conductor reduces resistance and energy loss, while the combined capacitance sources compensate for the increased area usage.
Solution Approach 2:
By changing the capacitance parameter through the addition of a bridge conductor, the patent reduces the required inductance value. This allows the conductor to be wider with lower resistance, reducing energy loss while maintaining the same resonant frequency operation.
4Reliability
If shielded straps with bridge conductor are used to increase capacitance, then effective capacitance increases and inductor area is reduced, but device complexity increases
Solution Approach 1:
The bridge conductor serves multiple functions: it acts as a shield, provides additional capacitance, and couples electromagnetic fields. By making this single element perform multiple functions, the patent increases effective capacitance and reduces inductor area without proportionally increasing device complexity.
Solution Approach 2:
The shielded strap structure with bridge conductor provides multiple benefits simultaneously: it increases capacitance, reduces inductor area, improves shielding, and enhances coupling. This multi-functionality allows the patent to achieve better operational efficiency while keeping the added complexity manageable through a unified structure.
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 reduces the area occupied by the inductor, increases the effective capacitance, and enhances the operational efficiency and range of the RFID tag by allowing for a smaller loop inductor and wider conductor, which reduces energy loss.
Implementation Method 1
the second conductor, the first strap conductor, and an antenna conductor are arranged to overlap each other to provide a mutual area with separating dielectrics such that the second conductor, the first strap conductor, and an antenna conductor are coupled via a plurality of capacitors
Implementation Method 2
The resonant element is typically the combination of an inductor formed as part of the antenna and the capacitance of the RFID chip, and is capable of performing a number of different functions. For example, the resonant element may be part of a network matching the impedance of the chip and antenna for optimum power transfer, or coupling magnetically to a reader system at or near the resonant frequency
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A method of using shielded straps with RFID tag designs is disclosed. Specifically, the RFID device, in one embodiment, comprises a bridge conductor which couples the antenna and pair of strap pads together. Thus, the coupling between the bridge conductor and the strap conductor, the coupling between the bridge conductor and the antenna conductor, and the coupling between the antenna conductor and the strap conductor increases the total capacitance of the RFID strap device. Further, the presence of the bridge conductor also reduces the area occupied for a given inductance, and provides a higher effective capacitance when the bridge strap is connected to the antenna.