3D Phase-Based Passive Source Location Using Parallel Processing
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Solution Overview
Problem
Existing passive source localization (PSL) methods face challenges in accurately localizing omnidirectional radio frequency (RF) transmitters due to restrictions on antenna spacing and the need for receivers to be in the far-field of the transmitter, which limits their applicability and accuracy.
Innovation Solution
A PSL system using multiple processing cores to perform parallel computations and search a three-dimensional region for an emitter location where phase estimates from distributed sensors are in good agreement, allowing for accurate localization without the need for close antenna spacing or far-field assumptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If receivers are spaced less than a half wavelength apart, then phase difference measurements become ambiguous, but increasing spacing introduces computational complexity and requires far-field assumptions
Solution Approach 1:
The patent transitions from two-dimensional phase difference measurements to three-dimensional phase-based localization. By using phase information in three dimensions and incorporating receivers at different spatial positions, the system achieves unambiguous direction finding without the half-wavelength spacing constraint that plagues traditional 2D PDOA methods.
Solution Approach 2:
The patent divides the localization problem into multiple independent phase measurements from distributed receivers. Each receiver provides an independent phase measurement, and the system combines these segments of information through computational processing to achieve accurate 3D localization without requiring all receivers to be closely spaced.
2Device complexity
If receivers are placed in the far-field of the transmitter, then wave-fronts can be assumed planar simplifying calculations, but this limits the applicability to nearby or omnidirectional transmitters
Solution Approach 1:
The patent changes the fundamental parameter used for localization from planar wave-front assumptions to spherical wave-front modeling. By accounting for the actual spherical propagation of RF waves and using phase differences in three dimensions, the system accurately localizes transmitters at any distance without requiring far-field approximations.
Solution Approach 2:
The patent replaces the mechanical/geometric approximation of planar wave-fronts with an electromagnetic field-based approach that directly models RF wave propagation. This substitution allows accurate localization near the transmitter where wave-fronts are clearly spherical, eliminating the need for far-field assumptions.
3Measurement precision
If multiple receivers are distributed in three-dimensional space, then localization accuracy improves without far-field assumptions, but computational time increases
Solution Approach 1:
The patent performs preliminary computations by pre-calculating phase difference vectors and storing them in lookup tables or pre-processing the spatial relationships between receivers and potential transmitter locations. This preliminary action reduces the computational burden during actual localization operations.
Solution Approach 2:
The patent uses computational models and simulations to create virtual representations of the localization problem. By pre-computing phase relationships in a simplified or virtual environment, the system can quickly determine transmitter locations in the actual physical environment without performing complex real-time calculations.
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 computational time and eliminates the ambiguity in direction, enabling accurate localization of omnidirectional transmitters with spaced receivers, enhancing applications like cognitive radio and passive radar systems.
Implementation Method 1
PDOA for phase-based PSL
Implementation Method 2
RF transmitters can be localized... Phase-based passive source location
Data Source
AI summary
Passive location of an emitter is achieved by sensing a signal propagated from the emitter at multiple sensing locations and determining its phase at each sensing location. A three-dimensional region is searched to find an emitter location for which phase estimates of the signal at the emitter location are in good agreement among the sensing locations. An iterative search from a set of starting points in the region may be performed. The region may be subdivided and each region searched in parallel using multiple processors in parallel. Phase at the sensing locations may be determined locally, using synchronized clocks at the sensing locations, or at a common receiver. In the latter case, signal propagation time from the sensing location to the receiver location is taken into account. The emitter may be a wireless endoscopy capsule, for example.