Phase Locking in AC Magnetic Tracking Systems
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Solution Overview
Problem
Wireless magnetic tracking systems face challenges in determining the phase of the transmitter signal without ambiguity, leading to inefficiencies due to the need for separate resonant circuits to operate at both main and second harmonic frequencies, which increases complexity and power consumption.
Innovation Solution
Incorporating a transmitter with co-located orthogonal coils driven by a main sinusoidal component and a marker component with a known amplitude and phase relationship, close in frequency, allowing the receiver to process sensor signals and determine phase accurately, even when the main and marker components interfere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate resonant circuits operate at both main and second harmonic frequencies to determine phase without ambiguity, then phase determination accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines the main frequency and second harmonic frequency operations into a single resonant circuit by operating at twice the main frequency (2f0) while using frequency division to generate the marker signal at the fundamental frequency (f0). This eliminates the need for separate resonant circuits for each frequency, reducing device complexity while maintaining phase determination accuracy through the phase relationship between the marker and sensor signals.
Solution Approach 2:
The single resonant circuit performs multiple functions: generating the main AC signal at frequency f0, generating the marker signal at frequency 2f0 through frequency multiplication, and enabling phase determination through the known phase relationship between these signals. This multi-functionality reduces the number of components needed while maintaining measurement precision.
2Measurement precision
If separate resonant circuits operate at both main and second harmonic frequencies to determine phase without ambiguity, then phase determination accuracy is improved, but power consumption increases
Solution Approach 1:
The patent merges the power consumption of two separate resonant circuits into a single resonant circuit operating at 2f0. By using frequency multiplication and division rather than maintaining two independent high-Q resonant circuits, the system reduces total power consumption while still providing the necessary phase reference for unambiguous phase determination.
3Device complexity
If a single resonant circuit operates at twice the main frequency with frequency division, then device complexity is reduced, but signal interference occurs between main and marker components
Solution Approach 1:
The patent converts the potential harmful effect of signal interference into a beneficial feature by using the known phase relationship between the marker signal at 2f0 and the sensor signal at f0. The interference pattern itself contains phase information that can be used for determination, and the fixed phase relationship (90 degrees) between these frequency components provides a reliable reference for unambiguous phase measurement.
4Use of energy by moving object
If high-Q resonant circuits are used to efficiently apply main and marker frequencies, then power consumption is reduced, but frequency bandwidth is narrowed
Solution Approach 1:
The patent changes the operating frequency parameter to 2f0 for the resonant circuit, allowing the use of a high-Q circuit with narrow bandwidth at this specific frequency. Frequency multiplication and division then generate the required signals, enabling the system to operate efficiently with high-Q resonant circuits while still providing the necessary frequency components for the tracking system.
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 enables efficient operation with high-Q resonant circuits, reducing power consumption and complexity by allowing both main and marker frequencies to be applied with good efficiency, while accurately determining the phase and position of the receiver relative to the transmitter.
Implementation Method 1
a sender or transmitter which applies magnetic fields in space, and a sensor which detects the fields
Implementation Method 2
a resonant circuit having a resonant frequency equal to or very close to the main frequency
Data Source
AI summary
Plural transmitter coils of a magnetic locating system are driven with widely-separated main frequencies. One of the transmitter coils is also driven with a marker frequency close to the main frequency applied to that coil. The receiver determines a phase relationship with the transmitter based on the main and marker frequencies, so that the receiver does not suffer from phase ambiguity. The main and marker frequencies may interfere with one another, and the receiver may correct for such interference based on known characteristics of the signals at the main and marker frequencies.