Passive Tilt Sensing via Antenna Detuning for Door State Detection

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Solution Overview

Problem

Existing sensor systems for determining the state of components, such as doors, require complex and power-consuming active components, increasing system complexity and power consumption.

Innovation Solution

A passive tilt-sensing device that utilizes a detuning mechanism to modify the frequency of a local oscillator based on the orientation of a movable surface, using a moveable component that shifts proximity to an antenna to alter the antenna's frequency, allowing for state determination without powered mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If active powered sensors are used to determine component states, then measurement precision and reliability are improved, but device complexity and power consumption increase

Engineering Contradiction:

Improvestate detection accuracyVSAvoidsensor system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces active electronic sensing mechanisms with a passive mechanical field interaction system. A movable component physically modulates the antenna's electromagnetic field based on its position, eliminating the need for powered sensors while maintaining state detection capability through frequency shifts in the wireless signal.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses the movable component itself as the sensing element. The component's position automatically modulates the antenna's electrical characteristics without requiring separate sensing mechanisms, power sources, or active electronics. The load-bearing structure performs the sensing function passively through its interaction with the electromagnetic field.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If active powered sensors are used to determine component states, then measurement precision is improved, but power consumption increases

Engineering Contradiction:

Improvestate detection accuracyVSAvoidsensor power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The movable component serves multiple functions simultaneously: it performs its primary mechanical function (e.g., door operation) while also acting as the sensing element that modulates the electromagnetic field. This eliminates the need for separate powered sensors, reducing overall system power consumption while maintaining detection accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If passive sensing mechanism is used, then device complexity and power consumption are reduced, but measurement precision may deteriorate

Engineering Contradiction:

Improvesensor system complexityVSAvoidstate detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system detects state changes by measuring frequency shifts in the wireless signal caused by the movable component's position. By monitoring changes in the electromagnetic field's resonant frequency rather than using active sensing, the system maintains measurement precision while reducing complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The electromagnetic field serves as an intermediary between the movable component and the detection system. The movable component modulates the field's characteristics, and the frequency shifts in this intermediary field provide precise state information without requiring direct contact or active sensing of the component itself.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The passive approach reduces system complexity and power consumption by eliminating the need for active components, enabling efficient detection of door states through frequency shifts in the tilt-sensing device.

Implementation Method 1

a moveable component configured to shift between a first location that applies a capacitive load to the antenna component and a second location that does not apply the capacitive load to the antenna component

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS12578191B1Passive sensing mechanism

Publication Date: 2026.03.17 AMAZON TECH INC

AI summary

Systems and methods are provided for determining the tilt-state of a moveable surface using a batteryless mechanism. A tilt-sensing device may be coupled to a moveable surface, such that the tilt-sensing device changes orientation in a manner corresponding the orientation of the moveable surface. The tilt-sensing device may include an antenna and a moveable component. The moveable component may change locations as the tilt-sensing device changes orientation due to gravitational forces. When the tilt-sensing device is in a substantially horizontal orientation, the moveable component may cause a distribution of material on the antenna. The distribution of material may detune the antenna by applying a load. Signals transmitted by the antenna may be shifted with respect to an expected frequency range. An external computing device may determine the tilt-state of the tilt-sensing device based on the presence or absence of a shift within received signals from the tilt-sensing device.