Location System Using Carrier Phase Prediction
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Solution Overview
Problem
Current location systems using TDOA and phase-based tracking techniques face challenges in achieving high accuracy and resolution, particularly with UWB restrictions and phase ambiguity issues, which lead to increased power consumption and measurement frequency, especially when tracking fast-moving targets.
Innovation Solution
A location system with at least three fixed stations and a mobile station that calculates the mobile station's location based on the time of arrival and carrier wave phase of radio signals, using a prediction unit and error reduction algorithm to predict the time of arrival and correct for phase shifts, allowing for high accuracy without the need for initial location acquisition and reducing measurement frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pulse width of a pulse signal is decreased to increase time of reception measurement resolution, then the measurement precision is improved, but the signal occupied band width increases which causes regulatory issues and reduces adaptability
Solution Approach 1:
The patent changes the fundamental parameter used for location calculation from time of reception (requiring narrow pulse widths) to carrier phase difference. This parameter substitution allows achieving high measurement precision (1 cm or less) without increasing signal bandwidth, thereby avoiding regulatory restrictions and maintaining system adaptability across different frequency bands including 2.4 GHz ISM band.
2Measurement precision
If phase-based tracking is used to achieve high distance resolution, then the measurement precision is improved, but phase ambiguity occurs every 360 degrees which reduces reliability
Solution Approach 1:
The patent employs feedback mechanisms where the calculated location information is fed back to resolve phase ambiguity. By using multiple fixed stations and comparing phase differences, the system can determine absolute location and correct for 2π ambiguities, ensuring reliable and unambiguous location acquisition.
Solution Approach 2:
The patent transitions from one-dimensional phase measurement (prone to ambiguity) to multi-dimensional location calculation using multiple fixed stations. By incorporating spatial information from multiple stations, the system resolves phase ambiguity and achieves reliable absolute location determination.
3Productivity
If measurement frequency is increased to track fast-moving targets accurately, then the productivity is improved, but the power consumption increases
Solution Approach 1:
The patent uses preliminary action by predicting the location of fast-moving targets based on previous measurement results. This prediction allows the system to maintain accurate tracking of moving objects without requiring extremely high measurement frequencies, thereby reducing power consumption while still achieving effective tracking.
4Measurement precision
If initial location acquisition is required for phase-based tracking, then the measurement precision can be maintained, but the device complexity and measurement frequency requirements increase
Solution Approach 1:
The patent implements self-service by enabling the system to automatically acquire absolute location information without requiring external initialization or manual input. The carrier phase difference method, combined with multiple fixed stations, allows the system to self-determine absolute position, eliminating the need for complex initial location acquisition procedures.
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 achieves high accuracy in locating the mobile station with reduced power consumption and lower measurement frequency, effectively addressing the limitations of UWB restrictions and phase ambiguity, enabling precise tracking without initial location acquisition and minimizing signal collisions.
Implementation Method 1
a mobile station that transmits a radio signal to each of the fixed stations
Implementation Method 2
predicts, from a time of arrival of the radio signal in a preceding posteriori period, a time of arrival of the radio signal in a following posteriori period by using a carrier wave phase difference of the radio signal
Data Source
AI summary
A time of arrival t and a carrier wave phase ϕ of a positioning pulse that is transmitted from a mobile station in each posteriori period and that is received by each of at least three fixed stations are input. Then, by using an error reduction algorithm, a time of arrival tk+1 of the positioning pulse in the following posteriori period is predicted by using a carrier wave phase difference Δϕ of the positioning pulse. Then, by using the predicted time of arrival t of the positioning pulse, the location of the mobile station is calculated. A time interval dt of a posteriori period is set to a time interval with which a difference Δϕnm between the carrier wave phase differences, which is changed by the movement of the mobile station at an assumable maximum movement speed, is no greater than 180°.