Microwave Ranging Sensor Using Three-Frequency Phase Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dual technology motion detectors, combining Doppler microwave frequency (MW) and passive infrared (PIR) sensors, face limitations in detecting intruders when cloaked, moving directly at the detector, or in high ambient temperatures, and are prone to false alarms, especially with pets triggering false alerts due to the PIR sensor's field of view limitations and ambiguity in distance measurement by common Doppler MW sensors.
Innovation Solution
A method using three MW signals of different frequencies to accurately determine the distance of an intruder by calculating phase differences and selecting true distance measurements, eliminating ambiguity, and setting precise signal thresholds based on empirical data to differentiate between human and pet signals, thereby reducing false alarms and enhancing detection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual technology detector combines PIR and MW detectors to eliminate false alarms, then reliability is improved, but the detector still fails to accurately detect intruders in specific situations (cloaked, down the throat, high temperature) and cannot distinguish pets from intruders
Solution Approach 1:
The patent segments the detection system into three independent MW detection channels operating at different frequencies (F1, F2, F3), each processing signals separately through dedicated circuits. This segmentation allows the system to measure phase differences between channels to determine distance, enabling accurate discrimination between intruders and pets based on spatial information rather than relying solely on PIR confirmation.
Solution Approach 2:
The patent introduces an intermediary processing stage that calculates phase differences between the three MW signal channels to determine target distance. This intermediary distance measurement capability allows the system to make intelligent decisions about alarm generation without requiring PIR sensor confirmation, thereby eliminating the limitations of dual-technology detectors while maintaining high reliability.
2Ease of operation
If common Doppler MW sensors are used to detect motion, then ease of operation is improved, but distance measurement ambiguity causes false alarms for objects outside the protected space or vibrations within it
Solution Approach 1:
The patent divides the MW detection into three separate frequency channels (F1, F2, F3), each with its own signal processing path. By measuring phase differences between these segmented channels, the system resolves distance measurement ambiguity that plagues single-channel Doppler sensors, eliminating false alarms while maintaining operational simplicity.
Solution Approach 2:
The patent changes the detection parameter from simple motion detection to phase difference measurement across multiple frequencies. By analyzing how phase relationships change between three different frequency channels, the system accurately determines distance without the ambiguity inherent in conventional single-frequency Doppler measurement, thereby improving measurement precision without complicating operation.
3Area of stationary object
If PIR sensor field of view is used for detection, then coverage area is improved, but pet immunity is worsened due to cone-shaped field of view sensing IR from pets at distances
Solution Approach 1:
The patent introduces an intermediary distance measurement mechanism based on phase difference analysis of three MW frequency channels. This intermediary spatial information allows the system to distinguish between objects at different distances from the sensor, enabling it to ignore pets within the field of view while maintaining detection of actual intruders, thereby achieving pet immunity without sacrificing field of view coverage.
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 enhances the detection of intruders by accurately measuring distance and reducing false alarms, improving pet immunity and the reliability of MW motion detectors, allowing for precise threshold setting to reliably detect intruders while discriminating against animals and vibrations.
Implementation Method 1
a Doppler microwave frequency (MW) detector... transmits a MW signal and receives a reflected MW signal from the intruder
Implementation Method 2
receives reflected signals from an intruder in the protected space corresponding to each of the three different frequencies
Implementation Method 3
The PIR detector senses infrared radiation (IR) from the intruder
Data Source
AI summary
A method for detecting an intruder in a protected space that uses a microwave frequency sensor to determine an accurate distance measurement to the intruder. The accurate distance measurement reduces the false alarms typically associated with microwave frequency sensors due to motion outside the protected space and vibration within the protected space. The motion detector transmits three microwave frequency signals of different frequencies in order to eliminate an ambiguity problem when determining the accurate distance measurement. The accuracy of the intruder distance measurement may be determined with greater resolution by reiteratively transmitting and evaluating microwave frequency signals of different frequencies. The motion detector of the present invention may include a PIR sensor. The accurate distance measurement allows the motion detector to precisely set signal threshold levels for the microwave frequency detector and the passive infrared detector to reliably detect an intruder while discriminating against an animal or other moving object.