Portable Iterative Geolocation of RF Emitters Using TDOA and FDOA
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Solution Overview
Problem
Existing methods for geolocating RF emitters require a minimum of three or four distinct geographic locations for two-dimensional and three-dimensional positioning, respectively, which can be impractical in situations where fewer receivers are available or where signals lack timing information.
Innovation Solution
A method and apparatus using a portable geolocation sensor that iteratively moves to different locations to receive and time-stamp RF emissions, allowing for geolocation with a single sensor or multiple sensors, including the use of timing signal receivers, tunable wideband receivers, and signal processors to compute the emitter's location using data from multiple acquisitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If classical TDOA geolocation is used with multiple sensors at distinct geographic locations, then unique emitter location can be determined, but the requirement for minimum three sensors (2D) or four sensors (3D) increases device complexity and operational difficulty
Solution Approach 1:
The patent transforms the static requirement of having multiple fixed sensors into a dynamic solution where a single sensor moves to multiple locations. The sensor sequentially occupies different geographic positions (first location, second location, third location) to collect signal data, thereby achieving the geometric diversity needed for unique emitter location determination without requiring multiple simultaneous sensors.
Solution Approach 2:
The patent adds the time dimension to the traditional spatial approach. Instead of requiring multiple sensors to be present simultaneously at different locations, the single sensor moves through space over time, collecting data at different positions at different times. This temporal sequencing allows the system to achieve the same geometric baseline coverage that would otherwise require multiple co-located sensors.
2Measurement precision
If multiple sensors are deployed simultaneously at different locations, then emitter location can be determined, but the ease of operation deteriorates due to the need for precise timing synchronization and coordination between multiple sensors
Solution Approach 1:
The patent extracts the timing synchronization requirement from the system by using a single sensor that sequentially visits multiple locations. This eliminates the need for complex inter-sensor timing synchronization and coordination protocols that would be required if multiple sensors operated simultaneously. The single sensor only needs to record its own position and timestamp, greatly simplifying operational complexity.
Solution Approach 2:
The single sensor performs all measurement functions independently without requiring coordination with other sensors. The sensor autonomously navigates to different locations, records signal data, and stores position information, thereby eliminating the operational complexity associated with multi-sensor synchronization and data correlation.
3Measurement precision
If signals with timing information are used for geolocation, then accurate location can be achieved, but the adaptability deteriorates because signals lacking timing information cannot be processed
Solution Approach 1:
The patent changes the processing parameters from time-domain analysis (requiring timing information) to frequency-domain analysis using FDOA (frequency difference of arrival). By measuring the frequency difference of the emitter signal between different sensor locations, the system can determine emitter position without requiring the signal to contain embedded timing information, thereby expanding compatibility to include signals that lack such timing properties.
Solution Approach 2:
The patent creates a universal geolocation method that can process both signals with timing information (using TDOA) and signals without timing information (using FDOA). The single-sensor iterative approach with frequency-based processing enables the system to handle a broader range of signal types, including commercial wireless communications signals that may not have readily accessible timing properties.
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 geolocation of RF emitters with fewer sensors and without requiring timing information in the signal, improving location accuracy through iterative data acquisition and sensor relocation, while providing guidance for optimal sensor placement based on Geometric Dilution of Precision analysis.
Implementation Method 1
a tunable wideband receiver for receiving and processing signals from an emitter of interest (EOI)
Implementation Method 2
a timing signal receiver for receiving timing signals
Implementation Method 3
computing the location of the EOI using data representative of the EOI transmissions stored during the first and second periods of time
Data Source
AI summary
Iterative geolocation of a stationary RF emitter through the use of TDOA may include the use of a single portable geolocation (e.g., TDOA) sensor, a pair of portable geolocation sensors and three of more portable geolocation sensors. Adding portable geolocation sensors to the iterative process reduces the constraints on the signals to be located as well as providing a reduction in the number of iterations required to obtain improved location accuracy.