Passive Radio Source Localization Using Time-of-Arrival Clustering

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Solution Overview

Problem

Existing methods for detecting unauthorized radio transmitting devices, such as drones, are ineffective due to their reliance on prior characterization and are difficult to locate using traditional radar, especially when made from low-density materials like polymers.

Innovation Solution

A method using time-of-arrival techniques with multiple sensors to passively locate radio emission sources by calculating signal locations based on arrival times and applying cluster filters to determine convex or elliptical boundaries, allowing for estimation of radio emission source locations without prior knowledge of transmission frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional radar methods are used to detect drones, then detection capability is limited, but the patent achieves accurate detection and location of radio emission sources including drones made from low-density materials

Engineering Contradiction:
Improvedetection capabilityVSAvoiddifficulty of locating
Core Design Contradiction:
ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent replaces traditional radar (electromagnetic wave reflection-based detection) with a radio signal monitoring system that detects emissions from drone communication modules. Instead of actively illuminating the target with radar waves, the system passively monitors radio frequency signals in the 2.4 GHz and 5.8 GHz bands, which are commonly used by drone controllers and telemetry systems. This substitution enables detection of drones made from low-density materials that are difficult to detect with traditional radar.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces radio frequency signals as an intermediary to detect drone presence. Rather than directly detecting the physical drone body, the system detects the radio emissions from the drone's communication module. The signal processing unit analyzes these intermediary radio signals to infer the presence, location, and movement of the drone, effectively using the radio communication as a detectable signature of the drone's operation.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If prior characterization of drones is required for detection, then detection reliability improves, but the patent enables detection without prior knowledge of transmission frequencies or drone types

Engineering Contradiction:
Improvedetection reliabilityVSAvoiddetection flexibility
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal detection system that can identify multiple types of radio emitting devices without requiring device-specific configuration. The signal processing unit analyzes radio signals across multiple frequency bands (2.4 GHz and 5.8 GHz) and uses pattern recognition to identify characteristic emission patterns of various drone types, controller systems, and telemetry modules. This universal approach allows the system to detect unauthorized drones, locate licensed transmitters, and identify device types without prior characterization or database lookup.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent dynamically adjusts detection parameters based on the analyzed radio signals. The system monitors signal strength, frequency, modulation patterns, and temporal characteristics to automatically adapt its detection criteria. By changing detection parameters in real-time based on observed signal characteristics, the system maintains high reliability across different drone types and operating conditions without requiring pre-programmed knowledge of specific devices.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If multiple sensors are deployed to improve location accuracy, then location precision improves, but system complexity and cost increase

Engineering Contradiction:
Improvelocation accuracyVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent divides the detection and location system into multiple geographically distributed sensor units, each equipped with radio receivers and signal processing capabilities. Each sensor independently monitors radio emissions and calculates preliminary location data. The central processing unit then integrates data from multiple sensors to determine precise location through triangulation or multilateration methods. This segmentation allows the system to achieve high location accuracy while maintaining modular architecture that simplifies deployment and reduces individual sensor complexity.

Inventive Principle:
Principle #1Segmentation

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 accurate and efficient detection and tracking of radio emission sources, including drones, by calculating signal locations and applying cluster filters to enhance location estimation accuracy and reduce false positives.

Implementation Method 1

Time-of-arrival methods, based on differences in transit time between an actively emitting object and a number of sensors

Methodology Applied
Scientific EffectTime of arrival measurement: Time of Flight

Data Source

PatentUS12487318B2Radio location finding
Publication Date: 2025.12.02 CRFS
  • US12487318B2 patent drawing
  • US12487318B2 patent drawing
  • US12487318B2 patent drawing

AI summary

A method for passively locating a radio emission source is described. The method includes receiving radio signal datasets corresponding to each of three or more sensors that includes at least one radio receiver, receiving or retrieving a physical location that define a convex hull corresponding to each sensor determining whether an emitter signal within a target frequency range is present in any of the radio signal datasets, and assigning any radio signal dataset which includes the emitter signal as a detection dataset. In response, a signal location is calculated based on arrival times of the emitter signal and the respective physical locations. A locus of possible positions is generated based on calculating two or more alternative signal locations One or more estimated radio emission source locations is output based on a respective cluster of signal locations.