RFID Reader Tag Location via Multi-Frequency Constellation Mapping
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Solution Overview
Problem
UHF RFID systems face challenges in maintaining a controlled reading zone due to multi-path transmission issues, leading to field nulls and cross-reading problems in manufacturing and logistics applications, which existing solutions fail to address effectively for both stationary and moving tags.
Innovation Solution
A method using a radio frequency identification (RFID) reader that transmits signals on at least two frequencies, combines the reflected signals to form a combined received signal, and maps this signal to a constellation diagram to accurately locate tags, eliminating field nulls and distinguishing between tag and external reflective objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If UHF RFID systems use far-field electromagnetic transmission for tag identification, then the tag accessing speed is fast and tags can be read at individual item level, but multi-path transmission causes field nulls and cross-reading problems making it difficult to maintain a controlled reading zone
Solution Approach 1:
The patent divides the reading zone into multiple sub-zones using multiple antennas arranged in space. Each antenna or antenna group forms a controlled reading sub-zone, allowing independent control of reading areas. This segmentation resolves the contradiction by maintaining fast access speed across the entire zone while enabling reliable control in each sub-zone, eliminating field nulls and cross-reading problems through spatial division.
Solution Approach 2:
The patent transitions from a single-point reading control to a multi-dimensional spatial reading control by deploying multiple antennas in three-dimensional space. This dimensional expansion creates multiple overlapping reading zones that can be independently controlled, resolving the contradiction between fast tag access and reliable reading zone control by adding spatial freedom to the system.
2Device complexity
If a single frequency is used for RFID communication, then the system is simple, but phase difference measurement cannot distinguish between tag reflections and external reflective objects
Solution Approach 1:
The patent combines multiple frequency signals (first frequency f1 and second frequency f2) into a unified measurement system. By merging the phase difference measurements from different frequencies and mapping them to a constellation diagram, the system achieves precise tag location while maintaining reasonable complexity. The combination of multi-frequency data provides the measurement precision needed to distinguish tag reflections from external reflections.
Solution Approach 2:
The patent changes the frequency parameter from a single value to multiple values (f1 and f2). This parameter change enables the system to measure phase differences at different frequencies, which when combined and mapped to a constellation diagram, provides sufficient precision to distinguish between tag reflections and external reflective objects while keeping the system manageable.
3Reliability
If multiple frequencies are used to improve tag location accuracy, then the reading zone control reliability improves, but the system complexity increases
Solution Approach 1:
The patent creates a virtual simplified model of the complex multi-frequency signal processing by mapping the combined signals to a constellation diagram. This graphical representation serves as a copy that simplifies the analysis and interpretation of multi-frequency phase difference data, reducing the cognitive and computational complexity while maintaining the reliability benefits of multi-frequency operation.
Solution Approach 2:
The constellation diagram acts as an intermediary between the raw multi-frequency signal data and the final tag location determination. It translates complex phase difference measurements from multiple frequencies into a visual and intuitive representation that simplifies the decision-making process for distinguishing tag reflections from external reflections, thereby reducing processing complexity while maintaining high reliability.
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 enhances the accuracy of tag location and filtering, reducing ambiguity and improving the reliability of the reading zone control, even in complex environments, by utilizing frequency diversity and pattern recognition on the constellation diagram.
Implementation Method 1
UHF RFID has many superior properties, such as fast tag accessing speed, cheap tags, and the ability to perform tagging at the level of individual items
Implementation Method 2
in view of the far-field electromagnetic transmission characteristics of UHF RFID, for instance, multi-path transmission
Implementation Method 3
the tag distance is measured by detecting phase difference in reflected carriers
Data Source
AI summary
A radio frequency identifying reader (RFID) and a method for locating a tag by the RFID includes transmitting, by the RFID reader, signals to the tag on at least two frequencies and receiving a corresponding reflection signal, combining, by the RFID reader, received reflection signals and acquiring the combined signal which is received, and mapping the combined signal that is received to a constellation point in a constellation map to locate the tag such that the tag can be more easily located.