Microwave Motion Sensor Reflector Masking Circuit
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Solution Overview
Problem
Current microwave motion sensors lack detection capabilities below the sensor and do not prevent tampering, especially when the security system is in an unarmed or disarmed mode, leading to potential disablement or masking of the sensors.
Innovation Solution
A method and apparatus that includes a microwave sensor with a reflector to enhance lookdown ability and a masking circuit to detect nearby motion when the security system is unarmed, initiating a mask condition signal, and an alarm circuit to indicate motion within the main protection zone when the system is armed, utilizing a downwardly shaped microwave signal and a second sensor with different technology positioned beneath the antenna.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microwave reflector is employed to enhance coverage and reduce blind zones beneath the sensor, then detection capability underneath the sensor is improved, but the strength of the main beam is reduced which is detrimental to detection in the protected region
Solution Approach 1:
The patent applies local quality by creating different microwave signal characteristics in different spatial zones. The reflector is designed to shape the microwave signal such that the main protected region receives strong signals for reliable detection, while the area underneath the sensor receives enhanced coverage through reflected signals. This spatial differentiation of signal quality resolves the contradiction between maintaining main beam strength and improving underneath detection.
2Ease of operation
If the security system is in unarmed mode, then the system is less restrictive and allows more freedom, but the sensor becomes vulnerable to tampering and masking
Solution Approach 1:
The patent implements preliminary action by detecting motion in a mask zone (area near the sensor) before the system is armed. When motion is detected in this zone while unarmed, the system preemptively sets a mask condition that prevents arming. This preliminary detection and prevention mechanism ensures sensor protection before potential tampering can occur, resolving the contradiction between system accessibility and sensor reliability.
3Area of stationary object
If the sensor monitors a large protected region, then the coverage area is improved, but the ability to detect nearby tampering attempts is reduced
Solution Approach 1:
The patent applies segmentation by dividing the monitoring space into distinct zones: a mask zone (near the sensor) and a main protected region (farther away). Each zone has its own detection parameters and response mechanisms. Motion in the mask zone triggers a mask condition, while motion in the protected region triggers an alarm. This spatial segmentation allows the system to maintain both broad coverage and precise nearby detection capabilities.
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
Enhances detection coverage below the sensor and prevents tampering by initiating a mask condition signal when motion is detected near the sensor in an unarmed state, ensuring the sensor's operability in an armed mode and providing comprehensive protection.
Implementation Method 1
MW motion sensors transmit a microwave signal toward a region to be monitored and in the event that movement is detected within the region, the microwave signal is reflected back (echo) from the movement and is modulated due to the Doppler Effect. When a signal is reflected from a moving object (target) it is shifted in frequency. This shift in frequency is called the Doppler Effect and is directly proportional to the targets velocity relative to the sensor.
Implementation Method 2
a reflector or strip of copper foil provides enhanced microwave amplitude at low incident angles, thereby effectively reducing a blind zone beneath the microwave transmitters by reflecting part of the main beam
Data Source
AI summary
A motion sensing method and apparatus includes a housing enclosing a microwave motion sensor including an antenna, and a security system. The antenna may be a patch antenna which includes microwave radiating elements for transmitting and receiving a microwave signal for sensing motion. A reflector is attached to the housing and positioned above the antenna for downward shaping of the microwave signal. The microwave radiating elements together with the reflector provide a radiation pattern where a main beam is transmitted in a direction orthogonal to a surface of the antenna and a sided lobe is transmitted downward in amplitude below the microwave motion sensor. An alarm circuit indicates when the microwave sensor detects motion in armed mode, and a masking circuit indicates when the microwave sensor detects motion in a mask zone when the security system is unarmed. A second sensor may be positioned beneath the microwave motion sensor.