RFID Antenna Narrow Gap to Prevent Microwave Arcing
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Solution Overview
Problem
RFID tags used in microwaveable food packages pose safety risks when exposed to microwaves due to voltage build-up and potential arcing, which can lead to deformation, sparking, and even fires.
Innovation Solution
The design of an RFID tag antenna with a very narrow gap of less than 80 μm, which reduces voltage build-up at microwave frequencies by creating a low impedance path for microwave currents, while maintaining normal operation at UHF frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional RFID tag with a larger gap (100-200 μm) is used, then the RFID functionality operates normally at UHF frequencies, but high voltage builds up at microwave frequencies causing safety risks such as arcing, sparking, and potential fires
Solution Approach 1:
The patent changes the critical parameter of gap length from conventional 100-200 μm to a reduced length of less than 80 μm. This parameter change transforms the electrical characteristics of the antenna, creating a low impedance path that prevents voltage build-up at microwave frequencies while preserving UHF RFID functionality. The reduced gap length fundamentally alters how the antenna interacts with electromagnetic fields at different frequencies.
2Object-affected harmful factors
If the gap length is reduced to less than 80 μm, then voltage build-up at microwave frequencies is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating a specifically engineered narrow gap region with distinct electrical characteristics. This localized feature (the sub-80 μm gap) has different electrical properties than the rest of the antenna structure, providing microwave frequency protection at the critical location while allowing the rest of the antenna to maintain standard manufacturing tolerances for UHF operation.
3Object-affected harmful factors
If a shielding layer is added as proposed in US 2018/0189623, then voltage build-up is limited, but the device complexity and production cost increase
Solution Approach 1:
The patent extracts and eliminates the need for additional shielding layers by integrating the microwave protection function directly into the antenna's fundamental structure through the reduced gap length. Instead of adding a separate shielding component, the solution is built into the essential antenna geometry, simplifying the overall device structure while achieving the same protective effect.
Solution Approach 2:
The reduced gap length serves multiple functions simultaneously: it maintains UHF RFID operational functionality and provides microwave frequency protection against voltage build-up. This multi-functional design eliminates the need for separate shielding components, reducing device complexity while achieving comprehensive electromagnetic compatibility.
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 narrow gap effectively reduces voltage build-up and current amplitude at microwave frequencies, thereby eliminating safety risks and maintaining the functionality of the RFID tag.
Implementation Method 1
The very high power levels and frequency of these microwaves will generate high voltages on the antenna, and in particular over the gap bridged by the RFID chip, since this gap is necessarily relatively small, typically in the range 100-200 μm. This high voltage may cause a breakdown and generate an arc
Data Source
AI summary
An antenna for an RFID (Radio Frequency Identification) tag comprises two antenna parts being arranged at opposite end areas of the antenna, and at least one intermediate part forming a bridge between the antenna parts. One of the at least one intermediate part comprises power feeding areas to be connected to an integrated circuit. Further, a first gap is arranged in one of the at least one intermediate part, and has a gap length of less than 80 μm, which forms a low impedance path for current at microwave frequencies.