Proximity Sensor Directional Coupler Blocking Detection
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Solution Overview
Problem
Proximity sensors used in monitoring tags and portable tracking devices struggle to differentiate between natural body reflections and intentional blocking of electromagnetic signals, leading to false alerts and potential incapacitation of the devices.
Innovation Solution
A proximity sensor utilizing a directional coupler and detector system that monitors the magnitude of reflected power to distinguish between body reflections and blocking objects, providing alerts only when the reflected power exceeds a threshold, and is designed to minimize body reflections by positioning the antenna appropriately and using pulsed transmit signals to enhance detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the proximity sensor monitors reflected power to detect blocking objects, then detection sensitivity is improved, but false positive alerts increase due to body reflections
Solution Approach 1:
The patent applies local quality by creating a directional coupling structure where the coupled port is spatially positioned to receive signals from specific directions. This allows the sensor to differentiate between reflections from different sources (body vs. blocking objects) based on their spatial characteristics, thereby maintaining high detection sensitivity while reducing false positives from body reflections.
Solution Approach 2:
The directional coupler acts as an intermediary element that mediates between the antenna and the detector. It selectively couples reflected signals based on their direction of origin, allowing the system to distinguish between legitimate blocking object reflections and false body reflections without reducing overall detection sensitivity.
2Volume of moving object
If the antenna is positioned closer to the body to minimize device size, then device compactness is improved, but body reflections increase causing false alerts
Solution Approach 1:
The patent extracts the directional discrimination function from the antenna positioning itself and transfers it to the directional coupler structure. This allows the antenna to be positioned close to the body for compactness while the directional coupler separately handles the discrimination of reflection sources, effectively removing the constraint that previously forced a trade-off between size and false positive rate.
Solution Approach 2:
The patent introduces a new dimension of spatial directionality through the directional coupler's coupled port orientation. Instead of solving the size-reflection problem by adjusting antenna position (one dimension), the solution adds a directional coupling dimension that independently filters reflections based on their origin direction, allowing compact positioning without increased false positives.
3Measurement precision
If pulsed transmit signals are used to enhance detection sensitivity, then detection capability is improved, but energy consumption increases
Solution Approach 1:
The patent employs periodic pulsed transmit signals instead of continuous transmission. The oscillator generates signals in periodic pulses, allowing the directional coupler and detector to sample reflected power at specific intervals. This periodic action maintains high detection capability during pulse intervals while significantly reducing overall energy consumption compared to continuous transmission.
Solution Approach 2:
The system skips between active detection phases (during pulses) and idle phases (between pulses). During the idle periods, no transmission occurs, allowing the system to maintain detection readiness without continuous energy expenditure. This skipping approach enables high detection capability when needed while minimizing average energy consumption.
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
Effectively detects and alerts on the presence of blocking objects, reducing false positives and ensuring continuous operation until the blocking object is removed, while minimizing battery load and temperature drift issues.
Implementation Method 1
a directional coupler having a first port and a second port connected together by a main line and a third port and a fourth port connected together by a coupled line, the first port being connected to the oscillator, the second port being connected to the antenna, and the third port being connected to a detector and acting as an isolated port of the directional coupler when a transmit signal is supplied from the oscillator to the antenna along the main line and as a coupled port when a receive signal is supplied from the antenna to the oscillator along the main line
Implementation Method 2
the detector provides an alert indicating the presence of a blocking object if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold
Data Source
AI summary
A proximity sensor can be used with a device that relies on GPS signals or other radio-frequency (RF) signals. The proximity sensor can be used to determine if the signals are being deliberately blocked by an object such as metal foil placed near it. The sensor includes an oscillator 2, a directional coupler 4 and an antenna 8. A third port 6c of the directional coupler acts as a coupled port when RF power that has been transmitted by the antenna 8 is reflected back to the antenna by a blocking object. The reflected RF power passes along a main line of the directional coupler 4 and a proportion is coupled to the third port 6c. A detector provides an alert if the magnitude of the power of the transmit signal that is reflected back to the antenna 8 in the form of a receive signal exceeds a threshold.