Passive RF Source Localization Using TDOA FDOA and Doppler Rate
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Solution Overview
Problem
Existing systems for passively locating a source of electromagnetic signals, such as radio signals, face challenges in achieving accurate and efficient position estimation due to high computational requirements, difficulty in aligning sample streams, and unreliable convergence in determining signal source locations, as well as the inability to determine transmission power without prior knowledge.
Innovation Solution
A method involving an iterative search process that varies only two offsets in each iteration, uses whitened difference equations to enhance convergence, and determines transmission power to validate location estimates, while employing multilateration techniques with known receiver positions to estimate signal source locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing multilateration techniques are used to estimate signal source location, then position estimation can be achieved, but computational requirements are high and convergence is unreliable
Solution Approach 1:
The patent transforms the original nonlinear location estimation equations into linearized forms by changing the mathematical parameters and representation. This linearization allows the use of simpler computational methods while maintaining estimation accuracy, directly reducing computational complexity without sacrificing measurement precision.
Solution Approach 2:
The patent divides the complex location estimation problem into separate component equations for different signal parameters (time of arrival, frequency of arrival, Doppler rate of arrival). By segmenting the problem into manageable parts that can be processed independently and then combined, the overall computational burden is reduced while maintaining accuracy.
2Measurement precision
If comprehensive search methods are used to align sample streams and determine location, then accuracy can be improved, but computing resource requirements increase
Solution Approach 1:
The patent performs preliminary alignment of sample streams using cross-correlation techniques before the main location estimation process. By pre-processing the data to establish initial alignment, the subsequent estimation requires fewer computational iterations and resources, reducing overall energy consumption while maintaining accuracy.
Solution Approach 2:
The patent replaces exhaustive brute-force search methods with optimized mathematical algorithms including linearized equations and iterative solvers. This substitution of computational mechanics reduces the computational resources required while achieving the same or better estimation accuracy.
3Loss of information
If existing methods are used to determine transmission power, then power estimation can be achieved, but prior knowledge of source location is required
Solution Approach 1:
The patent determines signal source location and transmission power simultaneously through a unified estimation process rather than sequentially. By performing location estimation first as a preliminary step within the same framework, the method enables subsequent power determination without requiring external prior knowledge, maintaining operational simplicity while recovering complete information.
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
Reduces computing resource requirements, enhances accuracy and speed of signal source location estimation, and improves operational efficiency by minimizing search effort and ensuring reliable convergence.
Implementation Method 1
obtaining a first set of equations that, for each of a plurality of receivers of the electromagnetic signal, relate time of arrival (TOA), frequency of arrival (FOA), and Doppler rate of arrival (DROA), to a range between the source and the particular one of the plurality of receivers
Data Source
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AI summary
The application relates to a method of estimating a location of a source of an electromagnetic signal. Also disclosed is a system comprising apparatus for carrying out the method, and a computer-readable medium storing a computer program for carrying out the method. The method includes: obtaining a first set of equations that, for each of a plurality of receivers of the electromagnetic signal, relate time of arrival (TOA), frequency of arrival (FOA), and Doppler rate of arrival (DROA), to a range between the source and the particular one of the plurality of receivers; selecting a candidate source location in three-dimensional space; obtaining a second set of equations by transforming each of the first set of equations based on a displacement vector; based on the second set of equations, obtaining a set of difference equations comprising, for each of a number of pairs of the receivers, respective equations representing a time difference of arrival (TDOA) between the pair, a frequency difference of arrival (FDOA) between the pair, and a Doppler rate difference of arrival (DRDOA) between the pair; obtaining a plurality of datasets, each dataset comprising successive data samples representative of the electromagnetic signal as received at a respective one of the receivers; comparing pairs of the datasets to determine respective measured TDOA, FDOA and DRDOA values; solving the set of difference equations by searching for a displacement vector that minimises a cost function; and iteratively arriving at an estimate of the location of the signal source.