Tag Positioning via Phase Difference and Frequency Offset
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Solution Overview
Problem
Existing location systems, such as GPS, face challenges in providing accurate and real-time position information, especially in indoor or areas with poor satellite coverage, and struggle with multipath effects in phase measurement systems.
Innovation Solution
A method that uses frequency offsets between a tag and receivers to improve position determination accuracy and speed, and to identify and compensate for multipath effects by receiving phase differences and frequency offsets from multiple signals transmitted at different times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If satellite positioning systems (GPS) are used to determine position, then position information can be obtained, but accuracy is limited to a few meters and response time is slow (several seconds or minutes)
Solution Approach 1:
The patent replaces satellite-based mechanical positioning systems with a local radio location system using fixed receivers and mobile tags. This substitution enables centimeter-level accuracy and real-time positioning by using phase difference measurements of radio signals instead of satellite signals, resolving the contradiction between measurement precision and response time.
Solution Approach 2:
The patent changes the measurement parameters from satellite signal phase to local radio signal phase differences between multiple receivers. By measuring phase differences at multiple fixed receivers and using these to calculate position through trilateration, the system achieves both high accuracy (centimeter level) and fast response (real-time) simultaneously.
2Measurement precision
If phase difference measurement systems are used to improve position accuracy, then accuracy increases, but multipath effects cause measurement errors that are difficult to detect and mitigate
Solution Approach 1:
The patent uses feedback by measuring phase differences at multiple fixed receivers and continuously comparing these measurements to calculate and update tag position in real-time. This multi-receiver feedback mechanism allows the system to detect and compensate for multipath effects, maintaining measurement reliability while achieving high accuracy.
Solution Approach 2:
The patent makes the phase difference measurement system universal by deploying multiple fixed receivers that can simultaneously measure phase differences from multiple tags. This multi-functional approach allows the system to handle both direct signals and multipath signals, improving reliability while maintaining accuracy through geometric dilution of precision (GDOP) optimization.
3Productivity
If radio location technologies are used to track objects in real-time, then position information can be obtained continuously, but system complexity increases with multiple receivers and signal processing requirements
Solution Approach 1:
The patent segments the positioning function into fixed receivers that only perform signal reception and phase measurement, and a central processing system that performs position calculation. This segmentation allows real-time tracking with simplified receiver design, as each receiver only needs to measure phase difference without complex computation, reducing device complexity while maintaining real-time productivity.
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 enhances the accuracy and speed of position determination, effectively mitigating multipath issues and providing reliable position information in challenging environments.
Implementation Method 1
receiving a phase difference between phases of two frequency components of a first signal transmitted by a tag at a first time and measured by a receiver
Implementation Method 2
receiving a frequency offset between the tag and the receiver for the first signal
Implementation Method 3
Each frequency offset may be dependent upon a difference in frequencies of clocks in the tag and the receiver and upon a velocity of the tag at time of transmission of the signal
Data Source
AI summary
A tag transmits signals having at least two different frequency components. The signals are receivable by at least some of a plurality of spaced receivers. Each receiver, in response to receiving a signal, measures respective phases of the first and second frequency components and a frequency offset between the tag and the receiver. The frequency offset is dependent upon a difference in frequencies of respective clocks in the tag and the receiver. A position processor obtains a difference in phases of the first and second frequency components for a signal, a frequency offset between the receiver and tag and determines the position of the tag in dependence upon the difference between respective phases of the first and second frequency components and in dependence upon the frequency offset.