TDOA Clock Synchronization via Over-Determined Aircraft Measurements
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Solution Overview
Problem
Existing Time Difference of Arrival (TDOA) tracking systems face challenges in synchronizing remote clocks without a beacon or GPS signal, particularly in portable systems or during GPS outages, leading to inaccurate position data for aircraft.
Innovation Solution
The system synchronizes remote clocks using over-determined TDOA measurements, leveraging real 3D space tracking and Kalman filter algorithms to estimate clock deviations, which does not require additional hardware and can function with multiple stations, including five or more, to achieve accurate time synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS or beacon signals are used for clock synchronization, then time synchronization accuracy is improved, but system reliability deteriorates when GPS is unavailable or beacons are lost
Solution Approach 1:
The system uses aircraft targets themselves to synchronize the clocks of multiple stations. By measuring TDOA from multiple stations to the same aircraft and using the over-determined equations, the system self-synchronizes without requiring external GPS or beacon signals. The aircraft's position serves as the reference for clock synchronization.
Solution Approach 2:
The patent introduces an intermediary approach by using the aircraft target as a mediator between stations to establish time synchronization. Instead of directly using GPS satellites or ground beacons as intermediaries, the system uses the measured TDOA data from aircraft positions to derive clock corrections, effectively making the aircraft the intermediary for synchronization.
2Measurement precision
If additional hardware is added for clock synchronization, then time synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
The system makes the existing TDOA measurement hardware serve dual purposes: both for aircraft position determination and for clock synchronization. The same receivers and signal processing equipment used for tracking aircraft are also used to measure TDOA for synchronization, eliminating the need for separate synchronization hardware.
Solution Approach 2:
The system uses its own operational data (aircraft positions and TDOA measurements) to perform clock synchronization without requiring additional dedicated synchronization hardware. The tracking system serves itself by using the same measurement infrastructure for both positioning and timing functions.
3Measurement precision
If five or more stations are used for over-determined measurements, then clock synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
The system uses five or more stations to create over-determined measurement equations, which provides redundant information that improves synchronization accuracy. The excessive number of stations (more than the minimum four needed for basic TDOA) creates additional constraints that refine the clock synchronization through least-squares optimization.
Data Source
AI summary
Disclosed are a method and a system for clock synchronization estimation using position over-determination principles applied to TDOA measurements of well-tracked targets with a height of about 5 km and higher. Clock correction factors or delays can then be applied to sensor clock signals, providing accurate tracking of targets such as aircraft, even in the event of GPS failure or jamming.