Phase Rate of Change Techniques for Passive Geo-Location
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Solution Overview
Problem
Existing systems for passively determining the geo-location of a radio frequency (RF) emitter using phase rate of change (PROC) measurements face challenges in achieving accurate and unique location estimates due to increased range ambiguities as long baseline interferometer (LBI) baselines and time intervals are extended.
Innovation Solution
A system employing a long baseline interferometer (LBI) and a short baseline interferometer (SBI) with a processor to determine phase rate of change (PROC) over different time intervals, select the closest range estimate, and combine with angle of arrival (AOA) measurements to accurately locate the RF emitter, potentially using multiple LBIs and SBIs and adaptive filtering to resolve ambiguities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LBI baseline length and PROC time interval are increased to improve geo-location accuracy, then measurement precision improves, but the number of range ambiguities increases making unique location determination unreliable
Solution Approach 1:
The patent segments the baseline into two parts: a long baseline (LBI) for high-precision PROC measurements and a short baseline (SBI) for unambiguous AOA measurements. This segmentation allows the system to exploit the strengths of both baseline lengths - the LBI provides the measurement precision needed for accurate geo-location, while the SBI provides the reliability needed to resolve range ambiguities through its unambiguous angle measurements.
2Manufacturing precision
If LBI baseline and time interval are extended to reduce measurement errors, then geo-location precision improves, but algorithm reliability deteriorates due to increased range ambiguities
Solution Approach 1:
The short baseline interferometer acts as an intermediary that bridges the gap between the long baseline's precise but ambiguous measurements and the need for unambiguous location determination. The SBI's unambiguous AOA measurements serve as a reference that helps select the correct range estimate from multiple ambiguous possibilities provided by the LBI, thereby reducing the complexity of ambiguity resolution.
3Reliability
If multiple LBIs and SBIs are used to resolve ambiguities and improve accuracy, then geo-location reliability improves, but device complexity increases
Solution Approach 1:
The patent merges the functional capabilities of multiple interferometers into a unified system where the LBI and SBI work together as an integrated pair. Rather than treating them as separate complex systems, the invention combines their measurement outputs through a coordinated processing algorithm that fuses the LBI's precise range-rate data with the SBI's unambiguous angle data, achieving high reliability without proportionally increasing overall system 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
The system effectively reduces range ambiguities and enhances geo-location accuracy by using phase rate of change measurements and angle of arrival data, allowing for precise determination of the RF emitter's location even with extended LBI baselines and time intervals.
Implementation Method 1
determine a first phase rate of change (PROC) of the RF signal received by the LBI
Implementation Method 2
long baseline interferometer (LBI) including a first antenna and a second antenna positioned on a vehicle to receive the RF signal
Implementation Method 3
short baseline interferometer (SBI) including a third antenna and a fourth antenna positioned on the vehicle to receive the RF signal
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The present invention relates to a system for resolving phase ambiguities in phase rate of change (PROC) measurements of a long baseline interferometer (LBI). The system includes an LBI having a first antenna and a second antenna positioned on a vehicle to receive the RF signal transmitted by the RF emitter, and a processor positioned on the vehicle. The processor is configured to determine a first phase rate of change (PROC) of the RF signal received by the LBI over a short time interval to produce a short time interval range estimate of the RF emitter, determine a second PROC of the RF signal received by the LBI over a long time interval which is greater than the short time interval, to produce a plurality of ambiguous long time interval range estimates of the RF emitter, and c) select one of the plurality of long time interval range estimates based on the short time interval range estimate.