Virtual Mirror Clock Synchronization for Moving Platform Time Offsets
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Solution Overview
Problem
Existing methods for synchronizing clocks between moving platforms, such as aircraft or ships, face challenges due to inaccurate GPS signals and insufficient accuracy for certain applications, especially when considering Doppler shifts and clock drifts over long distances.
Innovation Solution
The use of optical signals, specifically femtosecond pulsed lasers, to establish a virtual mirror system between platforms, allowing for precise synchronization of clocks by adjusting pulse repetition frequency and controlling optical power, enabling accurate timestamp sharing and relative positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS signals are used for clock synchronization between moving platforms, then the system complexity is reduced and ease of operation is improved, but the measurement precision and reliability deteriorate due to inaccurate GPS signals and insufficient accuracy for certain applications
Solution Approach 1:
The patent introduces optical signals as an intermediary medium for time transfer between moving platforms. Instead of relying on GPS signals, the system uses optical pulses transmitted between platforms to establish precise time relationships. The optical signal acts as a mediator that carries timing information directly between clocks, achieving picosecond-level synchronization accuracy without GPS dependency
Solution Approach 2:
The patent replaces the GPS-based electromagnetic signal system with an optical system using femtosecond pulsed lasers. This substitution transitions from radio frequency signals to optical frequency signals, enabling much higher precision time measurement. The optical domain provides finer time resolution and better immunity to Doppler effects compared to traditional GPS signals
2Measurement precision
If optical signals with femtosecond pulsed lasers are used for precise clock synchronization, then the measurement precision is improved to less than 10 picoseconds, but the device complexity and difficulty of detecting and measuring increase
Solution Approach 1:
The patent employs periodic optical pulse trains with femtosecond duration and precisely controlled repetition rates. By using periodic pulses instead of continuous waves or single pulses, the system creates multiple measurement opportunities and enables averaging techniques. The periodic nature allows for frequency domain analysis and simplifies the detection of time offsets through correlation methods
Solution Approach 2:
The patent uses optical pulses as copies of timing information that can be transmitted without significantly degrading the original time reference. Each optical pulse carries a precise timestamp from the source clock, creating a portable time reference that can be measured at the receiving platform. This copying approach allows the receiving platform to reconstruct the source clock's time scale with extreme precision
3Measurement precision
If Doppler shifts and clock drifts are considered in the synchronization method, then the measurement precision is improved, but the device complexity and calculation requirements increase
Solution Approach 1:
The patent implements feedback mechanisms where the measured time offsets and frequency drifts are continuously monitored and used to adjust the optical pulse generation and reception processes. The system measures the actual Doppler shift and clock drift occurring during transmission, then feeds this information back to correct subsequent measurements and maintain synchronization accuracy despite the moving platform conditions
Solution Approach 2:
The patent dynamically adjusts key parameters including the optical pulse repetition frequency, pulse duration, and transmission power based on the measured Doppler shift and relative velocity between platforms. By changing these parameters in response to measured conditions, the system maintains optimal measurement precision across varying operational scenarios without requiring overly complex processing
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 achieves clock synchronization with an accuracy of less than 10 picoseconds, effectively addressing the limitations of GPS signals and ensuring accurate data sharing and positioning between moving platforms.
Implementation Method 1
transmitting a first plurality of optical pulses to a second platform... receiving a first optical signal transmitted by a different platform through free space
Implementation Method 2
circuitry forming a virtual mirror... each of the second plurality of pulses is transmitted from the second moving platform at the same time each of the first plurality of pulses is received
Data Source
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AI summary
Aspects herein describe techniques for synchronizing clocks between two moving platforms using optical signals generated from lasers to measure clock offsets and determine a separation distance between moving platforms. Once the clocks are synchronized (e.g., an offset between the clocks is determined), the moving platforms can share sensor data, location data, and other information which is dependent on accurate timestamps and relative positions. In one aspect, one of the platforms serves as a virtual mirror. That is, the platform transmits a pulse at the same instance a pulse is received, similar to a mirror that reflects incident light. For example, the first platform may transmit pulses which are received at the second platform. The second platform can use optical or electrical components to form the virtual mirror that transmits an optical pulse to the first platform each time a pulse is received at the second platform.