SFCW RFID Reader Distance Estimation
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Solution Overview
Problem
Current radiolocation technologies using backscatter RFID tags face challenges in achieving high accuracy and long-range positioning due to factors like multipath echoes and fading, especially in outdoor environments, and require complex setups and synchronization, limiting their versatility and precision.
Innovation Solution
A system utilizing a special-purpose RFID reader that generates a stepped-frequency continuous wave (SFCW) RF interrogation signal, allowing for precise distance estimation between the reader and tag by processing received signal phases and strengths, and enabling multipath component sensing through advanced signal processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RFID readers are used for positioning, then the system is simple and low-cost, but the positioning accuracy and ranging precision are limited
Solution Approach 1:
The patent transforms the traditional single-frequency RFID interrogation signal into a multi-frequency stepped-frequency continuous wave (SFCW) signal. By changing the frequency parameter of the interrogation signal across multiple discrete steps, the system achieves phase-based distance measurement with significantly improved precision while maintaining RFID system simplicity
Solution Approach 2:
The patent replaces traditional optical positioning systems (which require complex mechanical setup and have limited range) with an RFID-based electromagnetic system. This substitution eliminates the need for optical sensors, line-of-sight requirements, and complex mechanical alignment, achieving both high precision and extended operational range
2Measurement precision
If optical sensors are used for high-accuracy positioning, then positioning precision is improved, but the range is limited and setup time increases
Solution Approach 1:
The patent makes the RFID system multi-functional by enabling it to perform both traditional identification/tracking functions and high-precision ranging functions simultaneously. The same RFID infrastructure serves dual purposes, eliminating the need for separate optical positioning systems and extending the effective operating range beyond what optical sensors can achieve
3Measurement precision
If traditional channel modeling methods are used, then measurement accuracy can be achieved, but the setup requires complex equipment and cable connections
Solution Approach 1:
The patent extracts and eliminates the need for complex synchronization equipment, Vector Network Analyzers, and physical cable connections between source and measurement nodes. By using the RFID reader's own transmitted signal as the reference and measuring the phase of the backscattered signal, the system achieves accurate channel modeling through wireless, equipment-free measurement
Solution Approach 2:
The system uses its own transmitted SFCW signal as the reference for measurement, eliminating the need for external frequency references or synchronized equipment. The RFID reader generates the signal and simultaneously uses it to measure the channel characteristics, achieving self-contained, autonomous operation
4Use of energy by moving object
If backscatter RFID tags are used for tracking, then the tags are small and low-power, but the ranging precision and operational range are limited
Solution Approach 1:
The patent changes the frequency parameter of the interrogation signal across multiple stepped frequencies, enabling the passive backscatter tag to convey distance information through phase modulation of the backscattered signal. This allows the low-power tag to achieve high ranging precision without active transmission or additional power consumption
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 provides accurate, high-precision radiolocation with improved communication ranges and reduced positioning errors, enabling accurate channel modeling and real-time location estimation in various environments without the need for complex setups, and can operate effectively in outdoor conditions.
Implementation Method 1
Backscatter RFID tags include an antenna that can receive an interrogation signal from a reader, and circuitry that can modulate and reflect/backscatter the modulated signal
Implementation Method 2
A distance between the RFID reader and the backscatter RFID tag may be estimated based on at least a summation of differences between RSPs corresponding to adjacent carrier frequencies
Data Source
AI summary
Systems and methods for radiolocation using backscatter RFID tags and a special-purpose reader that produces a SFCW RF interrogation signal comprising N carrier frequencies. A backscattered interrogation signal from a backscatter RFID tag is down-converted using at least a portion of the generated SFCW RF interrogation signal. RSP corresponding to the N carrier frequencies are determined. RSS may be determined to improve performance. A distance between the RFID reader and the backscatter RFID tag may be estimated based on at least a summation of differences between RSPs corresponding to adjacent carrier frequencies.