Dual Microwave PIR Detector Blockage Detection
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Solution Overview
Problem
Dual technology motion detectors fail to generate an alarm if either the PIR or MW sensor is blocked, leading to undetected range reduction and potential false alarms due to susceptibility to blockages.
Innovation Solution
A dual detector system that includes a MW sensor to determine the range and size of a target, using multiple range bins and a microprocessor to estimate the target range and compare it with the PIR coverage area, triggering an alarm or notification if the PIR sensor is blocked or its range is reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual detector systems use AND function requiring both PIR and MW sensors to detect intruders, then false alarms are minimized, but the system fails to alarm when either sensor is blocked
Solution Approach 1:
The system continuously monitors the operational status of both PIR and MW sensors by analyzing their detection patterns. When the MW sensor detects a target within the PIR sensor's expected coverage area while the PIR sensor fails to detect it, the system generates feedback indicating potential PIR blockage. This feedback mechanism allows the system to compensate for sensor failures and maintain reliable intrusion detection despite blockages.
Solution Approach 2:
The MW sensor acts as an intermediary that can detect targets even when the PIR sensor is blocked. By using MW technology as a backup detection mechanism, the system ensures that intruders can still be detected through the MW sensor's alternative detection path, preventing false negatives caused by PIR blockages while maintaining the AND function's false alarm reduction benefits.
2Area of stationary object
If PIR sensor range is reduced due to blockage, then detection coverage is compromised, but the system cannot automatically detect this range reduction
Solution Approach 1:
The system uses feedback from MW sensor measurements to monitor PIR sensor performance. By comparing MW-detected target positions and characteristics against expected PIR detection patterns, the system can detect when the PIR sensor's effective range is reduced due to blockage. This feedback loop enables automatic identification of range reduction without manual intervention.
Solution Approach 2:
The system replaces manual verification of PIR sensor range with automated electronic comparison between MW and PIR detection patterns. By using MW sensor data as a reference standard, the system electronically determines whether the PIR sensor is operating within its expected range, eliminating the need for physical inspection or manual measurement of detection coverage.
3Reliability
If the system uses MW ranging to detect target range and compare with PIR range, then PIR blockage can be detected, but device complexity increases
Solution Approach 1:
The MW sensor serves multiple functions: it detects intruders, determines target range, and monitors PIR sensor performance. By making the MW sensor multi-functional, the system avoids adding separate dedicated components for range measurement and blockage detection. The same MW detection circuitry is used for all purposes, reducing overall device complexity while maintaining reliable blockage detection capability.
Solution Approach 2:
The system merges the PIR and MW detection functions into a unified processing architecture where both sensor types are evaluated by the same microprocessor using integrated algorithms. By combining the detection, ranging, and blockage monitoring functions into a single processing system, the patent reduces complexity compared to having separate independent systems for each function.
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 PIR sensor blockages and reduces false alarms by ensuring that the system generates an alarm when the PIR range is reduced, minimizing false indications from small objects and maintaining reliable intrusion detection.
Implementation Method 1
MW technology often operates on the principle of phase shift or Doppler effect. 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.
Implementation Method 2
The PIR sensor detects the difference between the infrared energy emitted from an intruder and that emitted from the ambient environment.
Data Source
AI summary
Embodiments of the present invention are directed to a method and system for use of ranging MW to detect range reduction in a dual (MW/PIR) intrusion detector. Embodiments of the invention utilize a Doppler microwave system capable of detecting an object 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 and size is determined. Embodiments of the invention recognize cases of PIR range reduction by use of range limited MW stages configured for different ranges to determine the general range of the moving object. If the MW recognizes a moving object of sufficient size within the coverage area, and if no PIR signal is present, the PIR is recognized as being blocked or disabled and notification is provided.