Differential Emitter Geolocation Using Phase Differences
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional geolocation techniques face challenges in accurately determining the position of a wireless communication unit based on phase measurements, particularly due to differential clock rate errors and integer ambiguities, which affect the precision of location determination.
Innovation Solution
The method employs synchronized wireless receivers on moving platforms to measure phase differences between a wireless communication emitter of interest and a reference emitter, using differential and doubly-differenced equations to eliminate ionosphere effects and clock rate errors, and employs phase-locked loops and frequency-of-arrival measurements to calculate the emitter's location with sub-wavelength accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional geolocation techniques use phase measurements to determine position, then location determination can be achieved, but differential clock rate errors and integer ambiguities reduce measurement precision
Solution Approach 1:
The patent segments the geolocation problem into multiple components by using multiple receivers on different platforms, each measuring phase differences independently. The differential phase measurements from multiple platforms are then combined to resolve ambiguities and eliminate clock rate errors, achieving higher precision location determination.
Solution Approach 2:
The patent introduces a reference emitter at a known location as an intermediary element. By measuring phase differences between the unknown emitter and this reference emitter across multiple platforms, the system can eliminate differential clock rate errors and resolve integer ambiguities, thereby improving measurement precision and reliability.
2Measurement precision
If phase measurements are used for geolocation, then position can be determined, but ionosphere effects introduce errors that degrade measurement accuracy
Solution Approach 1:
The patent converts the harmful ionosphere effects into a solvable problem by using differential measurements. The ionosphere introduces phase errors that are common to both the unknown emitter and the reference emitter measurements. By taking the difference between these measurements across multiple platforms, the ionosphere effects cancel out, leaving only the geometric position information needed for accurate geolocation.
3Measurement precision
If differential phase measurements are used to geolocate emitters, then location can be determined, but resolving integer ambiguities and eliminating clock rate errors increases system complexity
Solution Approach 1:
The patent adds the dimension of multiple platforms and multiple measurements to resolve the ambiguities. By measuring phase differences across multiple platforms at different locations and times, the system creates an overdetermined system of equations that can be solved to eliminate integer ambiguities and clock rate errors, achieving precise location determination despite increased processing complexity.
Data Source
AI summary
An unknown location of a transmitter of interest is determined based on wireless signals transmitted by both the transmitter of interest and a reference transmitter positioned at a known location. The transmitted signals are received at a plurality of non-earthbound platforms each moving in a known manner, and phase measurements for each received signal are used to determine the unknown location.