RFID Tag Passive Antenna Circuit Range Extension
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Solution Overview
Problem
Current RFID tags, both with discrete integrated circuit chips and antennas, and 'coil-on-a-chip' varieties, suffer from a limited effective operating range, which restricts their application due to the challenges in assembling separate components and the cost associated with precise bonding, as well as the limited size and cost of the antenna in 'coil-on-a-chip' configurations.
Innovation Solution
The integration of a passive antenna circuit with a multi-turn coil and a capacitor, having a resonant frequency matching the RFID tag's operating frequency, is used to extend the operating range by allowing mutual inductive interaction with the RFID tag's antenna, which can be arranged co-planar and within a central opening of the coil, potentially with additional passive antenna circuits for further enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a discrete antenna is used with an RFID chip, then the operating range can be improved, but the assembly complexity and bonding cost increase
Solution Approach 1:
The patent integrates the antenna structure directly into the RFID chip substrate, merging two previously separate components (antenna and chip) into a single unified structure. This eliminates the need for separate assembly and bonding processes while maintaining the extended operating range benefits of a larger antenna structure.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support for the RFID chip, acts as the antenna structure itself, and enables electromagnetic radiation for communication. This multi-functionality eliminates the need for separate antenna components and reduces assembly complexity.
2Length of stationary object
If the antenna size is increased to extend operating range, then the communication distance improves, but the device size constraint is violated
Solution Approach 1:
The patent transitions from planar two-dimensional antenna patterns to three-dimensional helical coil structures. This dimensional change allows the antenna to achieve larger effective radiating area and extended operating range while maintaining a compact footprint that fits within typical RFID tag size constraints.
Solution Approach 2:
The helical coil structure is integrated within and around the RFID chip assembly, with the coil winding around a central axis that can accommodate the chip. This nested configuration allows the larger antenna structure to be contained within the spatial envelope of the compact RFID tag.
3Ease of manufacture
If a coil-on-a-chip configuration is used, then the manufacturing cost decreases, but the operating range is limited
Solution Approach 1:
The patent divides the antenna structure into multiple helical turns rather than using a single planar loop. This segmentation into multiple coils increases the effective inductance and radiating area, thereby extending the operating range while maintaining compatibility with standard coil-on-chip manufacturing processes.
Solution Approach 2:
The patent modifies key antenna parameters including increasing the number of helical turns, adjusting the coil diameter, and optimizing the winding pitch. These parameter changes enhance the antenna's inductance and radiation efficiency, extending the operating range without requiring fundamental changes to the manufacturing process.
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 significantly increases the operating range of RFID tags by a factor of five, combining the benefits of 'coil-on-a-chip' tags with discrete component tags while reducing assembly complexity and cost, and expanding their practical applications.
Implementation Method 1
a first passive antenna circuit comprising a first multi-turn coil and a first capacitor connected to the first coil. The passive antenna circuit has a resonant frequency substantially the same as the operating frequency of the RFID tag
Implementation Method 2
allowing mutual inductive interaction with the RFID tag's antenna
Data Source
AI summary
An RFID tag having an rfid integrated circuit and an antenna is combined with a first passive antenna circuit to provide an extended operating range. The first passive antenna circuit has a first coil and a first capacitor to tune the passive antenna circuit to a resonant frequency the same as the operating frequency of the RFID tag. The first coil has a central opening larger than the size of the antenna. The passive antenna circuit is arranged with the antenna located in the central opening of the coil, preferably in a co-planar manner, to promote inductive interaction therebetween. A second passive antenna circuit essentially identical to the first, but having larger dimensions, is positioned with the coil of the second passive antenna circuit surrounding the first coil to extend the operating range even further.