Modified IRIG-B Time Code for Single-Channel Precision Transfer
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Solution Overview
Problem
Current high-precision time transfer technologies, such as IRIG-B, face limitations in transmission rate and message capacity, requiring additional channels for time interval messages and being costly due to complex coding modulation, especially in optical fiber systems designed for space channels and electric cables.
Innovation Solution
A modified IRIG-B time code format is introduced, increasing transmission rate by compressing code elements and adding message fields, allowing for more synchronous time messages to be carried, with an encoding and decoding method that synchronizes time signals and user-defined messages within a single channel using commercial optical fiber communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the standard IRIG-B time code is used for time transfer, then the implementation is simple and cost is low, but the transmission rate is limited to 100 bit/second and additional communication channels are required for time interval messages
Solution Approach 1:
The patent changes the transmission parameters of the IRIG-B code by increasing the baud rate from 100 bit/second to higher rates (e.g., 2400 bit/second or above) suitable for optical fiber transmission. This parameter change enables faster transmission while maintaining the basic IRIG-B encoding structure, thus improving productivity without completely abandoning the simplicity advantage.
Solution Approach 2:
The patent transitions the transmission medium from traditional space channels and electric cables to optical fiber, representing a dimensional change in the transmission domain. This enables higher transmission rates and allows all messages (time codes, time interval messages, control messages) to be transmitted through a single channel, eliminating the need for additional communication channels.
2Measurement precision
If TWSTFT with pseudo-random spread spectrum coding is used for remote time transfer, then sub-nanosecond precision is achieved, but complicated coding modulation and decoding are required making it costly
Solution Approach 1:
The patent extracts and removes the complex pseudo-random spread spectrum coding modulation and decoding components from the time transfer system. Instead, it uses simplified IRIG-B code encoding with direct optical fiber transmission, achieving the same sub-nanosecond precision through a much simpler implementation that eliminates costly complex coding systems.
Solution Approach 2:
The patent replaces expensive, complex TWSTFT coding modulation systems with a simpler, more economical approach using standard IRIG-B encoding over optical fiber. This substitution achieves comparable precision at lower cost, effectively using a cheaper alternative that doesn't require the sophisticated and costly spread spectrum infrastructure.
3Productivity
If code element width is compressed to raise transmission rate, then more synchronous time messages can be carried, but the code elements become more difficult to distinguish
Solution Approach 1:
The patent employs composite signaling techniques combining IRIG-B code elements with optical fiber transmission characteristics. By using specific optical encoding schemes and signal processing methods tailored to optical fiber, it maintains clear code element discrimination even at compressed widths and high transmission rates, effectively creating a composite system that leverages both the compactness of compressed codes and the high bandwidth of optical fiber.
Data Source
AI summary
A format for modified IRIB-G time code, with added message fields while preserving pulse width coding rule of the standard IRIG-B time code, having a time interval field for carrying time interval between the local time signal and a received time signal, and a user-defined or padded field for carrying user-defined time and/or control messages. An encoding and a decoding methods and devices for high-precision time transfer, where the modified IRIG-B time code carries more messages, and enabling transmission of timing messages and testing messages of two-way time comparison via a single message channel at the same time, which reduces fluctuation due to encoding and decoding manipulation and correlation with working frequencies via exact synchronization between the on-times of the output encoded time code and the transmitted time signal, and between the on-times of the output decoded time signal and the input time code, and improves precision of time transfer.