RFID Transponder Localization via Cross-Correlation
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Solution Overview
Problem
Existing RFID systems face challenges in accurately locating multiple RFID transponders within the same excitation field due to superimposed secondary fields, which complicates the assignment of measured field strengths to individual transponders without bidirectional communication and complex anti-collision protocols.
Innovation Solution
A method and device utilizing multiple sensors to generate measurement signals based on magnetic fields, determining the degree of correlation with a reference signal to isolate the strength and position of each RFID transponder through cross-correlation, allowing for orthogonal data sequences to separate individual field contributions and enable precise localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple RFID transponders are present in the excitation field simultaneously, then the quantity of transponders to be located increases, but the field strengths measured in the reader become superimposed and cannot be clearly assigned to individual transponders
Solution Approach 1:
The patent segments the superimposed magnetic field signal into individual transponder contributions by using cross-correlation with unique reference signals assigned to each transponder. This allows the reader to separate and identify the field strength contribution from each individual transponder even when multiple transponders are present simultaneously in the excitation field.
Solution Approach 2:
The patent introduces reference signals as an intermediary element that mediates between the superimposed transponder fields and the reader's measurement capability. Each transponder is associated with a unique reference signal, and cross-correlation of the measured field with these reference signals enables the reader to identify and quantify individual transponder contributions without direct bidirectional communication.
2Measurement precision
If bidirectional communication with complex anti-collision protocols is used to assign field strengths to individual transponders, then the measurement precision improves, but the device complexity and communication requirements increase
Solution Approach 1:
The patent enables transponders to be identified and located without requiring bidirectional communication or anti-collision protocols. Each transponder passively contributes to the magnetic field according to its unique reference signal, and the reader independently performs cross-correlation to identify and quantify each transponder's field strength contribution, eliminating the need for complex communication exchanges.
Solution Approach 2:
The patent replaces the mechanical/communication-based anti-collision protocol system with a signal processing approach using cross-correlation. Instead of requiring transponders to communicate bidirectionally and negotiate identification through complex protocols, the system uses the unique reference signals embedded in each transponder's magnetic field contribution and separates them through mathematical cross-correlation operations.
3Measurement precision
If cross-correlation with reference signals is used to separate individual transponder field contributions, then the measurement precision and localization accuracy improve, but the processing complexity increases
Solution Approach 1:
The patent performs preliminary action by pre-assigning unique reference signals to each transponder before the actual location measurement takes place. This allows the reader to have ready-made correlation templates for each transponder, enabling efficient cross-correlation processing during measurement without requiring complex real-time signal generation or adaptation.
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
Enables reliable and simultaneous localization of multiple RFID transponders without the need for bidirectional communication, using orthogonal data sequences to distinguish and separate field contributions, thus simplifying the localization process and reducing communication complexity.
Implementation Method 1
generating a plurality of measurement signals based on a magnetic field measured by a plurality of sensors
Implementation Method 2
determining a respective degree of correlation for each of the plurality of measurement signals with a reference signal as a measure of the strength of the portion of the magnetic field originating from the RFID transponder
Data Source
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AI summary
The invention relates to a method for locating an RFID transponder (140). The method comprises: generating a plurality of measuring signals based on a magnetic field measured by one of a plurality of sensors (110-1, 110-2, 110-3, 110-4) and (110-5); determining a corresponding degree of correlation with a reference signal for each of the plurality of measuring signals. The reference signal is based on a data sequence assigned to the RFID transponder (140); and determining a position of the RFID transponder on the basis of the degrees of correlation of the plurality of measuring signals. The invention further relates to an RFID system comprising: a device (100) for locating the RFID transponder (140); the RFID transponder (140), wherein the RFID transponder (140) generates a first field component (141) of the magnetic field, wherein the first field component (141) carries first data which is based on the data sequence assigned to the RFID transponder (140); and a further RFID transponder (150), wherein the further RFID transponder (150) generates a second field component (151) of the magnetic field, wherein the second field component (151) carries second data which is based on a further data sequence assigned to the further RFID transponder (150), the first data being orthogonal to the second data. The device (100) further comprises one or more exciter elements (130) for creating the magnetic exciter field (131) and a reference sensor (160) which generates a reference measuring signal. In addition to the field components (141, 151) of the RFID transponders (140, 150), the magnetic field comprises a field component (171) generated by a somewhat detached reference RFID transponder (170) to which a data sequence is also assigned. In effect the actual development of the field strength of the part of the magnetic field measured originating from the RFID transponder (140) is compared via the sensor positions with known reference developments for possible positions of the RFID transponder (140). The device (100) thus makes it possible to locate conventional LF and HF RFID transponders, for instance, one-dimensionally, two-dimensionally or three-dimensionally.