Equivalent Time Asynchronous Sampling for High-Speed Signals
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Solution Overview
Problem
Existing equivalent-time sampling methods for high-speed data signals face limitations, particularly in requiring a precise hardware trigger and losing sub-rate information when synchronizing data signals, and are unable to handle waveform temporal drift in optical transmission.
Innovation Solution
A sampling arrangement using two separate sampling gates to sample both the repetitive waveform and the trigger signal in parallel, with an algorithm processing the trigger samples to determine the time-base for the waveform, allowing for synchronization and visualization of high data rate signals without the need for a precise hardware trigger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional equivalent-time sampling uses a hardware trigger to generate the time-base, then the sampling can be synchronized to the waveform, but the system complexity and precision requirements increase significantly
Solution Approach 1:
The patent replaces the mechanical/hardware trigger system with a software-based algorithm. Instead of using a hardware trigger to generate the time-base, the system acquires samples at a fixed rate and calculates the time-base algorithmically by detecting zero-crossings or edges in the acquired samples. This substitution eliminates the need for precise hardware triggering while maintaining synchronization accuracy.
2Device complexity
If spectral analysis algorithm is used to determine time-base without trigger signal, then the system complexity is reduced, but sub-rate information is lost and waveform temporal drift cannot be visualized
Solution Approach 1:
The patent performs preliminary acquisition of trigger signal samples simultaneously with the data signal samples. By capturing the trigger signal samples in advance (or concurrently) at the same fixed sampling rate, the system preserves the timing reference information needed to recover sub-rate signals and detect temporal drift, while still avoiding complex hardware triggering requirements.
Solution Approach 2:
The patent uses the trigger signal samples as an intermediary reference. These samples serve as a mediator between the fixed-rate sampling system and the variable-rate waveform, enabling the algorithm to calculate accurate time-bases that preserve sub-rate information and temporal drift characteristics without requiring the sampling system to directly track the waveform frequency.
3Measurement precision
If real-time sampling with high speed A/D converter is used, then exact waveform characteristics can be visualized, but the sampling rate and cost increase significantly
Solution Approach 1:
The patent implements a dynamic time-base calculation approach where the sampling system operates at a fixed, lower rate but dynamically adjusts the time-base assignment of each sample based on algorithmic analysis of the trigger signal. This allows the system to accurately represent high-speed waveforms using a lower sampling rate by dynamically mapping samples to the correct time positions in the waveform period.
Data Source
AI summary
An asynchronous sampling arrangement utilizes sampling of both a high speed data signal and a trigger (clock) signal. The data signal may be either an optical signal or an electrical signal. The data and trigger signals are sampled in parallel by two separate gates, the gates based on the same strobe frequency. The samples corresponding to the trigger signal are then processed through an algorithm that determines the time-base related to the sampled signal. This established time-base is then used to reconstruct the sampled version of the high data rate input signal waveform.