Multi-protocol RFID Interrogator Step-Lock Synchronization
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Solution Overview
Problem
Existing RFID systems face challenges in operating multiple interrogators in close proximity due to interference issues, such as downlink on downlink and uplink on uplink interference, which limits their performance and capacity, especially in applications like toll collection systems where multiple lanes need simultaneous tag reading.
Innovation Solution
A multi-protocol RFID interrogating system employing a step-lock synchronization technique that synchronizes downlinks and uplinks across interrogators, allowing them to operate simultaneously and efficiently read both active and backscatter tags with minimal interference, using a single antenna and combining time division multiplexing with frequency separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple interrogators operate simultaneously in close proximity using frequency separation, then the system capacity and throughput are improved, but severe interference occurs between downlink and uplink signals
Solution Approach 1:
The patent implements a periodic time-division structure where all interrogators synchronize their downlink transmissions to occur during specific time frames, followed by uplink reception periods. This periodic coordination ensures that downlink signals from one interrogator do not overlap with uplink signals to another, eliminating the severe interference while maintaining high system capacity through parallel operation
Solution Approach 2:
The patent employs a feedback mechanism where interrogators exchange synchronization information and adjust their timing based on received signals from other interrogators. This feedback loop enables dynamic coordination of downlink and uplink time frames, allowing the system to maintain interference-free operation while adapting to varying traffic conditions and maximizing throughput
2Object-affected harmful factors
If time division multiplexing is used to prevent interference among closely located interrogators, then interference is eliminated, but the system speed performance deteriorates due to sequential operation
Solution Approach 1:
The patent segments the time domain into distinct downlink and uplink frames that are synchronized across all interrogators. By dividing the communication cycle into non-overlapping segments for transmission and reception, the system eliminates interference between closely located interrogators while maintaining parallel operation within each segment, thus preserving high speed performance
Solution Approach 2:
The patent merges the time-division multiplexing approach with frequency separation by allowing multiple interrogators to operate simultaneously on different frequencies during their assigned downlink and uplink frames. This combination enables parallel processing of multiple tags across different lanes without the speed penalty of purely sequential time division, achieving both interference elimination and high throughput
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 solution enables improved performance and increased capacity by eliminating severe forms of interference, allowing an unlimited number of toll lanes to operate without time sharing, thus enhancing the overall RFID system's efficiency and capability.
Implementation Method 1
RFID (radio frequency identification) systems use frequency separation and time domain multiplexing in combination to allow multiple interrogators to operate closely together within the bandwidth limitations imposed by radio regulatory authorities
Implementation Method 2
RFID (radio frequency identification) systems use frequency separation and time domain multiplexing in combination to allow multiple interrogators to operate closely together
Implementation Method 3
Backscatter RFID systems, because they are frequency agile, can use frequency separation to allow simultaneous operation of closely spaced interrogators
Data Source
AI summary
A multi-protocol RFID interrogating system employs a synchronization technique (step-lock) for a backscatter RFID system that allows simultaneous operation of closely spaced interrogators. The multi-protocol RFID interrogating system can communicate with backscatter transponders having different output protocols and with active transponders including: Title 21 compliant RFID backscatter transponders; IT2000 RFID backscatter transponders that provide an extended mode capability beyond Title 21; EGO™ RFID backscatter transponders, SEGO™ RFID backscatter transponders; ATA, ISO, ANSI AAR compliant RFID backscatter transponders; and IAG compliant active technology transponders. The system implements a step-lock operation, whereby adjacent interrogators arc synchronized to ensure that all downlinks operate within the same time frame and all uplinks operate within the same time frame, to eliminate downlink on uplink interference.