Dual Detector False Alarm Reduction via Range-Adjusted PIR Sensitivity
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Solution Overview
Problem
Dual motion detector systems face challenges in minimizing false alarms, particularly from small animals and insects, due to similar infrared energy levels and low-frequency signals from targets at varying distances, which current technologies fail to adequately address.
Innovation Solution
A system that combines Doppler microwave and passive infrared technologies, using multiple range bins to determine the target's range and adjust PIR sensitivity accordingly, optimizing detection for human presence while ignoring small animals and insects by adjusting pulse thresholds, duration, and frequency based on the target's range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PIR sensitivity is increased to detect human intruders, then detection capability is improved, but false alarms from small animals and insects increase
Solution Approach 1:
The PIR sensitivity is made dynamically adjustable based on the detected target range. The system automatically modifies the alarm threshold and sensitivity levels according to whether the target is in the far range (human detection mode) or near range (insect immunity mode), resolving the contradiction between detection capability and false alarm reduction
Solution Approach 2:
The system changes the PIR detection parameters (alarm threshold, sensitivity level) based on the target range determined by microwave detection. When a near-range target is detected, the system adjusts parameters to ignore insects; when a far-range target is detected, parameters are optimized for human detection
2Length of stationary object
If the PIR alarm threshold is lowered to detect distant targets, then detection range is improved, but susceptibility to small animal false alarms increases
Solution Approach 1:
The alarm threshold is dynamically adjusted based on target range. For far-range targets, a lower threshold enables detection of distant intruders. For near-range targets, the threshold is raised to prevent false alarms from small animals and insects, thus resolving the contradiction between detection range and reliability
3Reliability
If dual detector technology is used to minimize false alarms, then system reliability is improved, but device complexity increases
Solution Approach 1:
The microwave detector serves as an intermediary that first determines target range and type before the PIR detector makes its detection decision. This intermediary step allows the system to intelligently adjust PIR sensitivity based on target characteristics, achieving reliable false alarm minimization while managing complexity through coordinated operation of the two detectors
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 significantly reduces false alarms by accurately distinguishing between human and non-human targets, improving the overall accuracy of dual detector systems by dynamically adjusting PIR sensitivity based on the target's range, thereby enhancing the system's ability to detect intruders while minimizing false triggers.
Implementation Method 1
The PIR sensor detects the difference between the infrared energy emitted from an intruder and that emitted from the ambient environment
Implementation Method 2
MW technology often operates on the principle of phase shift or Doppler effect. Unlike PIR, MW technology is an active technology. The MW detector transmits MW energy, which reflects off objects and returns to the MW detector. Moving objects result in a received signal that is frequency shifted from the original transmitted signal
Data Source
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AI summary
Embodiments of the present invention is directed to a method and system for use of ranging MW to reduce dual (MW/PIR) intrusion detector false alarms. A Doppler microwave system may be provided that is capable of detecting an object range and adjusting the sensitivity of the PIR detector to account for object size and range. Multiple range limited MW stages may be configured for different ranges to determine the general range of the moving object. Based on signal levels present on these MW stages, an approximate object range is determined. The sensitivity of the PIR is then adjusted based on a PIR sensitivity vs. object range function that is optimized to alarm on humans and ignore small animals and insects.