RFID Transponder Location Tracking via Frequency Shifting
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Solution Overview
Problem
Current systems for tracking individuals within buildings, such as fire departments' accountability systems, face challenges with GPS signal degradation, inaccurate inertial tracking, and through-the-wall radar systems' inability to discern targets from clutter, making it difficult to reliably determine the location of individuals in mixed environments.
Innovation Solution
A system using transponders that emit frequency-shifted wireless electromagnetic signals in the radio or microwave frequency range, allowing for accurate tracking in three-dimensional space by a receiver with an array of antenna elements, which determines distance and direction through time-of-flight and phase analysis, providing location information for visual or data output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS systems are used to track location, then location determination is possible in open environments, but GPS signals rapidly deteriorate within buildings making tracking impossible indoors
Solution Approach 1:
The patent introduces RFID transponders as intermediary devices that are worn by firefighters and can be detected by fixed readers throughout the building. These transponders act as mediators between the tracking system and the firefighter, enabling indoor location determination where GPS fails by transferring the signaling function from satellite-based GPS to building-integrated RFID infrastructure.
2Measurement precision
If distributed Wi-Fi receivers are placed around a building to enable tracking, then location can be determined using trilateralization and triangulation, but it is time consuming to distribute receivers and determine positions
Solution Approach 1:
The system performs preliminary action by pre-installing fixed RFID readers at known locations throughout the building before emergencies occur. This advance deployment eliminates the time-consuming task of distributing and positioning receivers during urgent situations, while the pre-established network of readers with known positions enables immediate location determination through trilateralization and triangulation when firefighters need tracking.
3Ease of operation
If inertial systems with accelerometers are used to track movement, then movement away from starting point can be tracked, but localization accuracy decreases over time due to accumulated errors
Solution Approach 1:
The patent implements feedback by continuously comparing the firefighter's position, as determined by inertial sensors, against the actual position derived from RFID reader detections. When the RFID system provides a position update, it corrects the accumulated errors in the inertial navigation system. This feedback loop maintains measurement precision over time while preserving the ease of continuous tracking operation.
4Difficulty of detecting and measuring
If through-the-wall radar systems are used to locate targets, then targets behind walls can be detected, but the radar cannot discern firefighters from background clutter and debris
Solution Approach 1:
The patent applies the principle of making the target visually distinct from the background by having firefighters wear RFID transponders that emit unique frequency-shifted signals. This is analogous to color changes, where the transponder's frequency-modulated response creates a distinctive signal signature that allows the system to easily differentiate firefighters from background clutter, furniture, and debris that do not emit or modulate signals in the same way.
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 accurate tracking of individuals or objects within buildings and cluttered environments, improving safety and efficiency in emergency situations by providing precise location data.
Implementation Method 1
Each transponder includes a frequency shift stage such that the second wireless electromagnetic signal is responsively emitted at a different frequency relative to that of the first wireless electromagnetic signal
Implementation Method 2
The receiver has an array of antenna elements distributed across a three dimensional volume of space... used with a respective second wireless electromagnetic signal to determine the distance to a respective transponder
Data Source
AI summary
A system and bent-pipe transponder component for determining a location of an individual or object in three dimensional space. The system includes a transmitter configured to transmit a first wireless electromagnetic signal at a first frequency and at least one transponder that is configured to responsively emit a second wireless electromagnetic signal having a second frequency that is frequency-shifted from the first frequency. An included receiver detecting the first and second wireless electromagnetic signals is configured to provide an output of location information for the at least one transponder. A bent-pipe transponder component may include a receiving antenna, an emitting antenna, and a frequency shift stage comprising an oscillator and a first mixer, with the frequency stage mixing a received first wireless electromagnetic signal with the output of the oscillator via the first mixer to produce the emitted second wireless electromagnetic signal.