Single-Antenna Door and Window Opening Detection by Resonance Shift
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Solution Overview
Problem
Commercially available door/window opening detectors require two elements, increasing complexity and cost, necessitating a single-element solution for effective detection.
Innovation Solution
A single-element door/window opening detector using a quarter wavelength, inverted-F type antenna that changes resonant frequency based on proximity to a door or window, generating an alarm indication through a high frequency oscillator, coupler, detector, and analog-to-digital converter to determine the opening state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two elements (sensor element and magnetic element) are used for door/window opening detection, then detection reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the sensor element and magnetic element into a single integrated detector unit. The detector includes an antenna element that functions both as the sensing element and as the magnetic element, eliminating the need for separate components. This merging reduces device complexity while maintaining detection functionality through a single element that can sense both electromagnetic signals and magnetic field changes.
Solution Approach 2:
The single detector element is designed to perform multiple functions: it acts as both the sensor element for detecting electromagnetic signals and the magnetic element for generating magnetic field changes. This multi-functional design allows one element to replace the traditional two-element system, reducing complexity while preserving detection reliability.
2Reliability
If two elements (sensor element and magnetic element) are used for door/window opening detection, then detection functionality is improved, but implementation cost increases
Solution Approach 1:
By merging the sensor element and magnetic element into a single integrated detector, the patent reduces the number of components that need to be manufactured, assembled, and installed. This consolidation lowers implementation costs while maintaining the dual functionality needed for reliable door/window opening detection.
3Device complexity
If a single element is used for door/window opening detection, then device complexity is reduced, but detection precision may deteriorate
Solution Approach 1:
The patent employs parameter changes by utilizing different operating modes of the single antenna element. The detector measures both the amplitude and phase of reflected electromagnetic signals, and can operate at different frequencies to detect magnetic field changes. By changing measurement parameters rather than adding elements, the system maintains detection precision with reduced complexity.
Solution Approach 2:
The patent uses the reflected electromagnetic signal as an intermediary to detect both the presence and magnetic field changes. The antenna element interacts with the door/window material and its magnetic properties through electromagnetic reflection, allowing a single element to extract multiple detection parameters that maintain precision while reducing system complexity.
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
Enables reliable and cost-effective single-element detection of door/window openings by measuring changes in reflected electromagnetic signal intensity, reducing system complexity and implementation costs.
Implementation Method 1
radiating an electromagnetic signal and receiving a reflected electromagnetic signal
Implementation Method 2
a quarter wavelength, inverted-F type antenna which has a first resonant frequency when in proximity to a door made of a material having a given dielectric constant and a second resonant frequency when not in proximity to the door
Implementation Method 3
generating a direct electrical current corresponding to an intensity of the reflected electromagnetic signal, and converting the direct electrical current into a digital value
Data Source
Figure 1A
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Figure 2
AI summary
A door\window opening detector including an antenna having at least a first resonant frequency and a second resonant frequency associated therewith, the second resonant frequency being different from the first resonant frequency, the antenna having the first resonant frequency when in proximity to a door\window having a given dielectric constant and the second resonant frequency when not in proximity to a door\window having the given dielectric constant, and an alarm indication generator operable, in response to receiving an indication that a resonant frequency of the antenna has changed from the first resonant frequency to the second resonant frequency, for generating an alarm indication of opening of the door\window.