Real-Time Locating System Using Offset Clock Frequencies
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Solution Overview
Problem
RF ranging systems face challenges in maintaining synchronization of clocks for accurate distance calculations, are limited by regulatory constraints, and suffer from poor multipath performance and interference issues, particularly in indoor environments.
Innovation Solution
A locating system and method using initiators and transponders operating at different clock frequencies, with synchronization and skip cycle counting to calculate time adjustments for distance determination, employing direct-sequence spread spectrum techniques and ZigBee communication standards to achieve precise distance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If highly accurate synchronized clocks are used to calculate propagation time, then distance measurement precision is improved, but system complexity and cost increase due to clock synchronization requirements
Solution Approach 1:
The patent extracts the clock synchronization requirement from the distance measurement system by using one-way time of flight measurement with a single reference clock at the initiator, eliminating the need for synchronized clocks at both ends while maintaining measurement precision
Solution Approach 2:
The patent introduces a timestamp mechanism as an intermediary that records the departure and arrival times of signals, allowing propagation time calculation without requiring the receiving device to have a synchronized clock, thus resolving the synchronization complexity
2Length of stationary object
If continuous wave (CW) systems are used for long distance ranging, then ranging distance is improved, but multipath performance deteriorates and susceptibility to jamming increases
Solution Approach 1:
The patent uses periodic pseudorandom code sequences (chips) instead of continuous waves, allowing the receiver to correlate and distinguish direct signals from multipath reflections through code division, thereby maintaining long-range capability while improving multipath performance
Solution Approach 2:
The patent changes the signal parameter from continuous wave frequency to spread spectrum code sequence, enabling the system to achieve both long ranging distance and robust multipath rejection through correlation processing of the coded signals
3Adaptability or versatility
If ultra-wideband (UWB) systems are used to overcome regulatory constraints, then communication flexibility is improved, but system cost increases due to complex RF electronics
Solution Approach 1:
The patent employs simplified RF electronics that operate within FCC regulated bandwidth constraints, using cost-effective components and architectures that achieve adequate performance without the complex wideband RF front-ends of UWB systems
Solution Approach 2:
The patent adjusts the operational bandwidth parameter to comply with FCC regulations while maintaining effective ranging performance through optimized signal processing and timing measurements, avoiding the need for complex wideband hardware
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
The system provides accurate and flexible distance calculations, compliant with regulatory standards, and effective in various environments, including indoors, by using offset clock frequencies and skip cycle counting for precise time adjustments.
Implementation Method 1
An RF ranging system calculates the distance between two objects based on the time a radio signal propagates between the two objects and the speed of the radio signal
Implementation Method 2
In air, the radio signal propagates at a constant rate, roughly equal to the speed of light
Data Source
AI summary
A locating system, includes at least one initiator configured to operate at a first clock frequency, and to transmit a measurement signal including a first preamble; and at least one transponder configured to operate at a second clock frequency, to receive the measurement signal, and to transmit a response signal to the initiator, the response signal including a second preamble. The initiator is further configured to calculate, based on the response signal, a distance between the initiator and the transponder for determining a location of the transponder.