Phase-Based Synchronization in Magnetic Tracking Systems
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Solution Overview
Problem
Magnetic tracking systems face errors in determining the position and orientation of receivers due to phase ambiguity in wireless systems, particularly without a sync signal, and require additional hardware or user initialization for synchronization.
Innovation Solution
A method using direct digital synthesis (DDS) to generate orthogonal magnetic field frequencies, with a processor performing complex discrete Fourier transforms and phase rotations to synchronize the transmitter and receiver without additional hardware, by determining a confidence value and using the real part of the rotated complex signal matrix to resolve phase ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wireless magnetic tracking systems operate without a sync signal, then device complexity is reduced, but phase ambiguity occurs causing errors in position and orientation determination
Solution Approach 1:
The system performs self-synchronization by automatically determining phase relationships between transmitted and received magnetic field signals through signal processing algorithms. The processor computes correlation values and determines synchronization status without external sync signals or additional hardware, enabling the system to resolve phase ambiguity independently.
Solution Approach 2:
The patent replaces the mechanical/electrical sync signal transmission system with a signal processing-based synchronization method. Instead of using physical sync wires or additional transmitters to provide phase reference, the system uses computational algorithms to analyze phase relationships in the magnetic field signals themselves.
2Measurement precision
If additional hardware such as sync signals or IMUs is added to eliminate phase ambiguity, then measurement precision improves, but device complexity increases
Solution Approach 1:
The invention extracts the synchronization function from separate hardware components (sync signals, IMUs) and integrates it into the existing signal processing pipeline. By analyzing the magnetic field signals themselves for phase relationships and correlation patterns, the system extracts synchronization information without requiring additional dedicated hardware.
Solution Approach 2:
The processor performs multiple functions using the same hardware resources: it processes position and orientation data, determines synchronization status, and resolves phase ambiguity all through signal processing algorithms. This multi-functionality eliminates the need for separate sync hardware while maintaining measurement precision.
3Measurement precision
If user initialization is required to establish synchronization, then phase ambiguity is resolved, but loss of time increases due to repeated initialization
Solution Approach 1:
The system performs preliminary synchronization analysis continuously in the background by monitoring correlation values between transmitted and received signals. This preliminary action allows the system to be pre-synchronized or quickly re-synchronized without requiring user intervention, reducing initialization time while maintaining accuracy.
Solution Approach 2:
The synchronization process operates continuously rather than requiring discrete user-initiated initialization. The processor continuously monitors signal correlation and maintains synchronization status, ensuring the system is always ready for accurate measurement without time loss to repeated initialization 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
Enables synchronization of magnetic tracking systems without additional hardware or user intervention, maintaining accurate position and orientation determination of receivers in wireless systems, and allowing continuous tracking without initialization.
Implementation Method 1
a transmitter having a plurality of source magnetic coils configured to generate a magnetic field at orthogonal frequencies
Implementation Method 2
the receiver having a plurality of sensor magnetic coils configured to sense the magnetic field and generate magnetic sensor data
Implementation Method 3
perform a complex discrete Fourier transform on the magnetic sensor data from the sensor magnetic coils to determine a complex signal matrix (Sigmat) representing the phase of the sensed magnetic field frequencies
Implementation Method 4
rotate the complex Sigmat by rotating the phases of the sensed magnetic field frequencies to seek convergence of the complex Sigmat at a nearly real value
Data Source
AI summary
A system and method for performing synchronization of a magnetic field transmitter and receiver to resolve received signal phase ambiguity based upon the phases of the magnetic fields. Three orthogonal field frequencies are selected. A Fourier transform extracts the sine and cosine of the received signal, which provides the received signal phases and results in a complex signal matrix (“Sigmat”). A search is made for a phase rotation of the frequencies to achieve convergence of the Sigmat at a point it is real-valued; the search may be limited by aligning the Sigmat such that the major element becomes real-valued and rotating the other two frequencies. The correct phase is the one in which the Sigmat has a positive determinant and minimizes any remaining imaginary portion. A transmitter and receiver may be calibrated to account for any analog phase shift. Distortion of the magnetic field may also be detected and corrected.