3D Magnetoquasistatic Coupling for Long-Range Through-Wall Position Sensing
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Solution Overview
Problem
Existing indoor position sensing technologies using magnetoquasistatic fields face limitations in range and require a fixed infrastructure, increasing deployment costs and limiting applicability, as they are often restricted to short ranges and need multiple indoor nodes due to low-frequency signaling and ground/conductor effects.
Innovation Solution
The development of a bulk-conductivity theoretical model for magnetoquasistatic field-based position sensing that includes ground effects, enabling long-range through-the-wall position and orientation sensing using external nodes located far outside a building, with multi-axial quasi-static couplings and decoupled range from orientation and direction angles, allowing for infrastructure-less configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC coupling techniques are used for position sensing, then position sensing capability is achieved, but the range is limited to short distances (≤10 m) and high drive currents (≥12 A) are required
Solution Approach 1:
The patent employs AC signaling techniques with periodic modulation at frequencies between 2.5 kHz and 2 MHz, replacing DC coupling with time-varying magnetic fields. This periodic action enables position sensing while extending the operational range beyond the ≤10 m limitation of DC techniques, as the alternating fields can penetrate walls and propagate over longer distances through the environment.
Solution Approach 2:
The patent changes the operating frequency parameter from DC (0 Hz) to AC frequencies (2.5 kHz - 2 MHz) to resolve the contradiction. By operating at higher frequencies, the system achieves both position sensing capability and extended range, as the magnetoquasistatic fields at these frequencies can penetrate building structures and travel farther than DC fields while maintaining sensing accuracy.
2Measurement precision
If AC techniques at low frequencies (≤10 kHz) are used, then position sensing is achieved, but the range remains limited (≤10 m) due to Faraday's law
Solution Approach 1:
The patent increases the operating frequency parameter from low frequencies (≤10 kHz) to higher frequencies (2.5 kHz - 2 MHz, with optimal performance at 190 kHz and 2 MHz). This parameter change overcomes the Faraday's law limitations that constrain low-frequency AC techniques to short ranges, enabling the magnetic fields to penetrate walls and achieve longer operational distances while maintaining position sensing accuracy.
3Area of stationary object
If multiple indoor nodes are deployed to extend coverage, then coverage area increases, but device complexity and deployment cost increase
Solution Approach 1:
The patent uses building structures (walls, floors, ceilings) as intermediaries to propagate the magnetic fields throughout the indoor environment. Instead of deploying multiple nodes inside the building, a single external node transmits signals that penetrate through these structural intermediaries to cover the entire building area, thereby reducing the number of required nodes from multiple to one while maintaining comprehensive coverage.
Solution Approach 2:
The patent inverts the conventional approach by placing the sensing node outside the building rather than inside. This inversion allows a single external node to serve multiple indoor locations through wall penetration, eliminating the need for multiple indoor nodes and their associated complexity, while still achieving comprehensive coverage of the entire building.
4Length of stationary object
If higher frequencies (e.g., 2 MHz) are used to extend range, then range increases, but arbitrary power-law fitting is required due to multi-path and induced reflections
Solution Approach 1:
The patent optimizes the frequency parameter to specific values (2.5 kHz, 190 kHz, and 2 MHz) where the magnetoquasistatic approximation remains valid and environmental effects are minimized. At these carefully selected frequencies, the system achieves extended range while avoiding the need for arbitrary power-law fitting, as the field behavior follows predictable physical models that simplify signal processing and position calculation.
5Reliability
If nodes are placed close to or inside the building (≤2 m from wall) to improve signal strength, then signal coupling improves, but a fixed infrastructure is required which limits applicability
Solution Approach 1:
The patent uses the building structure itself as an intermediary medium to transmit magnetic fields from external nodes to indoor locations. This approach maintains reliable signal coupling through the walls and floors without requiring physical penetration or close proximity to the building, thereby preserving deployment flexibility and adaptability while achieving sufficient signal strength for position sensing.
Solution Approach 2:
The patent inverts the deployment strategy by positioning nodes outside the building rather than inside or close to it. This inversion eliminates the need for fixed infrastructure installation within the building while maintaining effective signal coupling through the building structures, thereby maximizing both reliability and adaptability for various deployment scenarios.
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 solution achieves extended range and coverage for entire buildings without the need for multiple indoor nodes, providing accurate 2D and 3D position sensing and orientation, invariant to device orientation, and reduces deployment costs by enabling position sensing from external nodes.
Implementation Method 1
Magnetoquasistatic (MQS) fields (AC/DC, alternating/direct current signaling) are not perturbed by low-loss dielectrics and are effective for position sensing of a mobile device in indoor environments
Implementation Method 2
ground effects are included into the theoretical developments to effectively model and enable the measurements for long-range applicability
Data Source
AI summary
Methods and systems for indoor position sensing are disclosed. The described methods and systems are based on magnetoquasistatic field coupling theory and can be implemented in two- and three-dimensional, long-range, through-the-wall applications, where the transmitting devices are implemented outdoor, the receiving device is implemented indoor, or vice versa. Measurement systems implemented to characterize the disclosed methods are also presented for both two- and three-dimensional applications involving indoor position sensing. Orientation sensing methods and systems are also disclosed.