RF Proximity Detection Using RFID Time-of-Flight Thresholds

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Solution Overview

Problem

Existing object location systems, such as RFID-based systems, are inefficient and costly for large-scale operations, and require extensive infrastructure and maintenance, while computer vision and GPS systems are expensive and complex, making it difficult to accurately locate objects in large areas.

Innovation Solution

Radio frequency (RF) proximity detection devices using passive and semi-passive RFID tags that transmit and receive RF signals to determine proximity based on time-of-flight or time-of-arrival, triggering user interfaces when objects are within a threshold distance, allowing for low-power, cost-effective object location.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If RFID-based object location systems are deployed, then object location capability is provided, but system cost and infrastructure complexity increase significantly

Engineering Contradiction:

Improveobject location accuracyVSAvoidsystem infrastructure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential proximity detection function from complex RFID systems, using simple passive tags and RF signal timing rather than full active RFID infrastructure. This selective extraction provides location capability while removing unnecessary system complexity and cost.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system uses inexpensive passive RFID tags that can be easily attached to objects, replacing expensive active RFID systems. These simple tags provide sufficient functionality for proximity detection without requiring powerful transmitters or complex reader infrastructure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Measurement precision

If active powered locator devices are used, then object location accuracy improves, but power consumption and device weight increase

Engineering Contradiction:

Improvelocation accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Passive RFID tags automatically respond to RF signals without requiring their own power source. The tags harvest energy from the incident RF fields, enabling location functionality while eliminating battery requirements and associated power consumption constraints.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system replaces active electronic positioning devices with passive RF signal-based detection. Instead of using powered motors, sensors, or processors in mobile devices, the system uses simple RF signal timing measurements to determine proximity and location.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If computer vision systems are deployed for object location, then visual recognition capability is achieved, but system cost and computational complexity increase

Engineering Contradiction:

Improveobject location accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces computer vision systems with RF signal-based detection. Instead of using cameras, image processors, and complex algorithms to track objects visually, the system uses simple RF signal timing measurements to determine object proximity and location, significantly reducing computational requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Adaptability or versatility

If RSSI-based RFID searching is used, then object search capability is provided, but search time and reliability decrease

Engineering Contradiction:

Improveobject search capabilityVSAvoidsearch time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The system uses time-of-flight measurements as direct feedback about object proximity. By measuring the round-trip time of RF signals, the system obtains immediate information about object distance without requiring complex search algorithms or multiple measurement cycles, significantly reducing search time.

Inventive Principle:

Principle #23Feedback

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 efficient and accurate object location with minimal hardware and power consumption, reducing costs and complexity by leveraging existing RFID infrastructure for proximity detection in large-scale environments.

Implementation Method 1

determine proximity based on time-of-flight or time-of-arrival

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Implementation Method 2

passive and semi-passive RFID tags that transmit and receive RF signals

Methodology Applied

Scientific EffectRF signal reflection: Reflection

Data Source

PatentUS20260024429A1Radio Frequency Proximity Detection Devices

Publication Date: 2026.01.22 ZEBRA TECHNOLOGIES CORP

AI summary

A method includes: transmitting, by a first radio frequency transceiver of a first device, a first signal; receiving, by the first radio frequency transceiver of the first device, a second signal in response to the first signal; determining a time value associated with the receiving of the second signal; determining that at least one of the time value or a distance value determined using the time value is less than or equal to a first threshold value, wherein the first threshold value is associated with the first device; and triggering a first output by a user interface component of the first device based on at least one of the time value or the distance value being less than or equal to the first threshold value.