Emitter Geolocation Using Sorted FDOA Observations
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Geolocation determination of a radio emitter using frequency difference of arrival (FDOA) measurements is affected by ambiguities caused by non-linear geometry resulting from aircraft maneuvers, leading to inaccuracies in estimation.
Innovation Solution
Sorting observations based on ambiguity levels, calculated using cone angle complements, and processing them with a Kalman filter to iteratively refine the geolocation estimate, or de-weighting high ambiguity observations to minimize their impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FDOA measurements are used for geolocation determination, then the geolocation can be estimated using observation points' locations and vector velocities, but ambiguities caused by non-linear geometry from aircraft maneuvers lead to inaccuracies in estimation
Solution Approach 1:
The patent applies preliminary action by sorting observations before processing them through the geolocation algorithm. Specifically, observations are sorted based on a sorting metric that evaluates their quality and reliability, ensuring that the most reliable observations are processed first. This preliminary sorting step prevents ambiguous observations from degrading the overall geolocation estimate, thereby resolving the contradiction between measurement precision and reliability under aircraft maneuvers.
2Measurement precision
If multiple observations are processed to improve geolocation accuracy, then more data is available for estimation, but high ambiguity observations can adversely affect the solution convergence
Solution Approach 1:
The patent applies local quality by treating different observations differently based on their individual characteristics. Instead of processing all observations uniformly, the system assigns different weights or processing priorities to each observation based on a sorting metric that evaluates local quality indicators such as signal-to-noise ratio, geometric dilution of precision, and ambiguity levels. This allows high-quality observations to contribute more to the geolocation estimate while minimizing the impact of ambiguous observations, thus maintaining both accuracy and convergence speed.
3Ease of operation
If observations are processed in the order they are received, then the processing is simple and fast, but the geolocation solution may diverge due to ambiguous observations appearing early in the sequence
Solution Approach 1:
The patent applies preliminary action by implementing a sorting step before the main geolocation processing. Observations are sorted based on a sorting metric that evaluates their reliability and quality characteristics. This preliminary arrangement ensures that reliable observations are processed first, establishing a solid foundation for the geolocation estimate before ambiguous observations are considered. While this adds a preprocessing step, it significantly improves solution convergence reliability with minimal additional computational complexity.
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 reduces the adverse effects of ambiguities, leading to a more accurate and convergent geolocation solution by prioritizing low ambiguity observations and mitigating the impact of high ambiguity observations, thereby improving the accuracy of radio emitter location estimation.
Implementation Method 1
A geolocation of a radio emitter can be determined using frequency difference of arrival (FDOA) measurements. FDOA measurements can be referred to as differential Doppler measurements.
Data Source
AI summary
A receiver operable to determine a geolocation of a radio emitter is disclosed. The receiver can identify a set of observations derived from signals emitted by the radio emitter. The signals can be detected via an antenna associated with the receiver. The receiver can identify an estimated location of the radio emitter. The receiver can calculate a cone angle complement for each observation in the set of observations. The cone angle complement can correspond to an ambiguity level of each observation. The receiver can sort the observations based on corresponding ambiguity levels to produce a set of sorted observations. The receiver can process, using a Kalman filter in the receiver, the set of sorted observations to iteratively refine the estimated location for determination of the geolocation of the radio emitter.