Phase Difference of Arrival Geolocation Using Satellite Phase Change Measurements
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Solution Overview
Problem
Conventional geolocation techniques using frequency difference of arrival (FDOA) measurements struggle to accurately determine the location of a transmitter when signal frequency changes due to oscillator drift and Doppler effects, as they require estimating the frequency of arrival from a frequency profile.
Innovation Solution
The use of phase change measurements over time from multiple satellite or airborne platforms, which allows for the determination of the transmitter's location by differencing the phase of a received signal across a temporal baseline, accommodating signal frequency changes and estimating the transmitter's location vector and average frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency difference of arrival (FDOA) measurements are used for geolocation, then location determination can be performed, but measurement accuracy deteriorates when signal frequency changes due to oscillator drift and Doppler effects
Solution Approach 1:
The patent changes the measurement parameter from frequency-based (FDOA) to phase-based (PDOA) measurements. Phase measurements are inherently more robust to frequency changes because they measure the instantaneous phase difference rather than requiring frequency estimation over time. This parameter transformation allows the system to maintain high location determination accuracy even when signal frequency changes due to oscillator drift or Doppler effects.
2Measurement precision
If signal duration is increased to improve frequency measurement accuracy, then measurement precision improves, but the system becomes less adaptable to frequency changes
Solution Approach 1:
The patent transforms the measurement approach from frequency domain (requiring long signal duration for accurate frequency estimation) to phase domain (providing instantaneous phase difference measurements). Phase measurements can be made over short time intervals without sacrificing accuracy, and they naturally accommodate frequency changes because they measure the phase at specific instants rather than requiring steady-state frequency assumptions.
3Ease of operation
If conventional FDOA techniques are used, then geolocation can be performed, but the complexity of handling frequency profiles increases
Solution Approach 1:
The patent extracts and measures only the phase component of the received signal, eliminating the need for complex frequency profile analysis. By focusing on phase difference measurements between multiple platforms, the system removes the complexity of tracking and analyzing frequency variations over time, while still achieving accurate geolocation through the simpler PDOA calculation method.
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 method enables accurate geolocation of a transmitter with rapidly changing signal frequencies by using phase change measurements from multiple platforms, improving location determination accuracy and handling frequency changes effectively.
Implementation Method 1
use a plurality of phase change measurements, made respectively at a plurality of satellite or airborne platforms over time, for a radio frequency signal transmitted by a stationary transmitter at an unknown location
Implementation Method 2
the situation is more complicated when the signal frequency changes due to oscillator drift and doppler changes
Data Source
AI summary
Geolocation is performed by receiving, at a plurality of non-earthbound platforms each moving in a known manner within a spatial coordinate system, a radio frequency (RF) signal transmitted from a transmitter at an unknown location on earth within the spatial coordinate system. For each of the platforms, a phase change of the received frequency carrier is measured over the same duration of time. The measured phase changes are combined to determine the transmitter location.