Multi-ship Coherent Geolocation for Airborne Radar Emitters
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Solution Overview
Problem
Existing passive geolocation systems for airborne radar emitters face challenges in accuracy due to high emitter speeds, resulting in positional ambiguities and lengthy data collection periods, and struggle to provide rapid location estimates.
Innovation Solution
The use of coherent processing of radar pulses by multiple spatially separated airborne collection platforms to simulate a virtual high-velocity collector, refining geolocation estimates through Doppler shifts and residue metrics, and maintaining a candidate history to eliminate ambiguous solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing passive geolocation systems are used for airborne radar emitters, then the system operates in listening only mode which reduces risk of detection, but positional ambiguities occur and many potential location solutions result
Solution Approach 1:
The patent combines data from multiple collection platforms (aircraft, ground stations, satellites) to perform coherent processing of radar pulses. By merging observations from multiple spatially separated platforms, the system resolves positional ambiguities that plague single-platform systems while maintaining passive listening-only operation.
Solution Approach 2:
The patent adds the dimension of multiple spatial platforms to the geolocation problem. Instead of relying on a single platform's ambiguous measurements, the system uses data from multiple platforms at different locations, transforming the problem from 2D ambiguous solutions to 3D constrained solutions that eliminate ambiguities.
2Device complexity
If existing passive geolocation systems are used, then the system operates with simpler architecture, but lengthy data collection periods are required to provide geolocation results
Solution Approach 1:
The patent performs preliminary coherent integration of radar pulses across multiple platforms before geolocation calculation. By pre-processing and combining data from multiple platforms in advance, the system reduces the total data collection period required while maintaining accurate geolocation results.
Solution Approach 2:
The patent implements continuous coherent processing of radar pulses across multiple platforms simultaneously. Rather than sequentially processing data from each platform, the system continuously integrates data from all platforms in parallel, dramatically reducing the time required to achieve sufficient integration for accurate geolocation.
3Measurement precision
If multiple spatially separated collection platforms are used, then geolocation accuracy improves, but the number of potential location solutions increases due to ambiguous solutions
Solution Approach 1:
The patent employs iterative refinement where initial geolocation estimates are fed back into the processing algorithm to eliminate ambiguous solutions. By using feedback from preliminary results to constrain subsequent processing, the system maintains high accuracy while eliminating spurious ambiguous solutions that arise from multiple-platform geometry.
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
This approach improves geolocation accuracy and reduces ambiguities, enabling rapid location estimates on the order of milliseconds compared to tens of seconds, while maintaining high-confidence candidate tracking.
Implementation Method 1
The geolocation calculation is based on Doppler shifts of the pulse repetition intervals (PRIs) of the emitter waveform
Data Source
AI summary
Techniques are provided for geolocation of an airborne radar emitting source. A methodology implementing the techniques according to an embodiment includes initializing a search grid with hypothesized emitter geolocations boxes of the grid. The method further includes refining geolocations based on calculated pulse repetition intervals of de-Dopplerized times of arrival (TOAs) of emitter pulses received at multiple collection platforms within a dwell period. A residue metric is employed to qualify candidate target geolocations based on differences between the measured TOAs and hypothesized TOAs associated with the refined geolocations. A candidate history tracks the geolocations of the candidates with the smallest residue over subsequent dwells, identifying such candidates that match locations in the history and updating counts of times the candidate has been matched. Candidates with lagging match counts are dropped from the history. The search grid size is reduced to encompass regions surrounding the viable candidates by a selected margin.