One-Pass Trigger Jitter Reduction in Digital Oscilloscopes
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Solution Overview
Problem
Digital oscilloscopes face significant challenges in quickly eliminating trigger jitter, which causes misalignment of acquisition records and affects the clarity of repetitive signal displays, due to inherent time delays and instability in trigger detection.
Innovation Solution
A system comprising a signal acquisition subsystem, acquisition memory, trigger detector, digital signal processor, edge detector, buffer memory, and trigger correction value generator, which processes digital samples to determine a trigger correction value, allowing for a 'one-pass' jitter-free display by correcting the trigger position in real-time, reducing the need for multiple memory retrievals and processing passes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional multi-pass trigger jitter correction is used, then trigger jitter is eliminated, but processing time is excessive
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing trigger correction values in a lookup table before actual signal processing. When a trigger event occurs, the system immediately retrieves the pre-computed correction value corresponding to the trigger address, eliminating the need for time-consuming real-time calculations during the display pass. This allows the system to achieve jitter-free display in a single pass while maintaining processing efficiency.
2Productivity
If trigger correction is performed in real-time, then display speed is improved, but processing accuracy may be compromised
Solution Approach 1:
The system performs preliminary computation of trigger correction values and stores them in a lookup table based on trigger addresses. During real-time operation, the system simply retrieves the pre-computed correction value corresponding to the measured trigger address, achieving both fast real-time correction and high precision without the computational overhead of on-the-fly calculations.
Solution Approach 2:
The patent introduces a lookup table as an intermediary structure that stores pre-computed trigger correction values. This lookup table acts as a mediator between the trigger detection system and the display system, allowing fast retrieval of accurate correction values without requiring complex real-time computations, thus resolving the contradiction between speed and precision.
3Measurement precision
If multiple memory retrievals are performed for jitter correction, then trigger alignment is improved, but system complexity increases
Solution Approach 1:
The patent pre-computes and stores trigger correction values in a lookup table before actual signal processing. During display operations, the system performs a single memory retrieval of the correction value from the lookup table based on the trigger address, eliminating the need for multiple iterative memory retrievals and complex alignment algorithms, thus reducing system complexity while maintaining precise trigger alignment.
Data Source
AI summary
A system and method: receive an input signal and output digital samples representing the input signal; store the digital samples for at least one acquisition record of the input signal in an acquisition memory; detect a trigger event in the input signal and calculate a trigger address in the acquisition memory for a digital sample corresponding to the detected trigger event; perform digital signal processing on the digital samples of the acquisition memory to produce processed digital samples; detect an edge, representing a trigger, in the processed digital samples, and determine a measured trigger time; temporarily store the processed digital samples in a buffer memory at least until the edge detector detects the edge in the processed digital samples; determine a trigger correction value in response to the measured trigger time; determine a corrected beginning address of the buffer memory from the calculated trigger address and the trigger correction value; and read the processed digital data out from the buffer memory beginning at the corrected beginning address.