FPGA Input Serializer Timing for Sub-Nanosecond Synchronization
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Solution Overview
Problem
Maintaining precise time synchronization between systems in low-cost multi-platform environments is challenging due to ambiguities caused by downstream sample clocks in field-programmable gate arrays (FPGAs), especially when relying on GPS strobes and clocks, resulting in timing inaccuracies near 10 nanoseconds.
Innovation Solution
A system and method utilizing an FPGA with an input serializer and x-bit wide shift register, where the signal passes through serializer shift registers in series, and the x-bit wide shift register is sampled at a slower clock speed to determine the time of signal arrival with sub-nanosecond accuracy, allowing for precise timestamping and synchronization across multiple systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS strobes and clocks are used to maintain time synchronization in multi-platform systems, then time synchronization is achieved, but timing ambiguities of close to 10 nanoseconds occur due to downstream sample clocks in FPGAs
Solution Approach 1:
The patent applies preliminary action by capturing the signal at the input pad and immediately shifting it through the x-bit wide shift register before any other processing occurs. This pre-capture and pre-shifting mechanism ensures that the timing information is preserved at the earliest possible moment, allowing the system to determine which clock cycle the signal arrived during, thereby eliminating the 10 nanosecond ambiguities that would otherwise be introduced by downstream sampling clocks.
Solution Approach 2:
The x-bit wide shift register acts as an intermediary between the input pad and the rest of the FPGA system. It captures the signal's arrival time information and holds it until the determination logic can process it. This intermediary structure preserves the precise timing information through the serialization process, enabling sub-nanosecond timing accuracy to be maintained despite the presence of downstream sample clocks that would otherwise introduce ambiguities.
2Productivity
If downstream sample clocks are used in FPGAs, then signal sampling is performed, but timing ambiguities close to 10 nanoseconds are introduced
Solution Approach 1:
The patent segments the timing measurement process into distinct phases: signal capture at the input pad, shifting through the x-bit wide shift register, and determination of the arrival clock cycle. By segmenting the process and using the shift register to capture the signal before downstream sampling, the system maintains precise timing information independent of the downstream sample clock rate, thereby achieving both high productivity and high measurement precision.
3Adaptability or versatility
If multiple systems operate independently with common time source, then system independence is maintained, but time synchronization between systems becomes difficult
Solution Approach 1:
The patent implements feedback by using the determined signal arrival time information to adjust and synchronize the timing across multiple independent systems. Each system captures its own signal arrival times with sub-nanosecond precision using the x-bit wide shift register mechanism, then uses this precise timing data to synchronize with other systems, maintaining both system independence and synchronization reliability.
Data Source
AI summary
A system may include a field-programmable gate array (FPGA). The FPGA may be configured to: determine a time corresponding to in which of x time periods a signal arrived at an input serializer based at least on a value; and determine a time when the signal arrived at an input pad based at least on a shift register latency value and the time corresponding to in which of the x time periods the signal arrived at the input serializer based at least on the value.