Waveform Display Compression for High- and Low-Frequency Signals
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Solution Overview
Problem
Current waveform compression methods in digital oscilloscopes, such as decimation and peak detection, either discard important high-frequency information or obscure low-frequency signals, leading to inaccurate representations of electrical signals over long periods due to high data rates exceeding memory limits.
Innovation Solution
A technique that simultaneously displays both a peak detected ('background') and a decimated/lowpass filtered ('foreground') version of the waveform, with adjustable intensity and color contrast to preserve information from both, allowing for effective compression and accurate representation of high and low frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If decimation is used to compress waveform data, then the compression ratio is improved, but high frequency information is lost and aliasing occurs
Solution Approach 1:
The patent divides the waveform data processing into multiple independent compression channels, each handling different frequency ranges or data subsets. This segmentation allows high-frequency components to be preserved in dedicated channels while other channels handle compression, resolving the contradiction between maintaining high-frequency information and achieving data compression.
Solution Approach 2:
The patent dynamically adjusts compression parameters such as sampling rate, filter cutoff frequencies, and compression ratios based on the detected signal characteristics. When high-frequency content is detected, the system modifies parameters to preserve these components while still achieving acceptable compression, thus resolving the contradiction between information preservation and data volume reduction.
2Loss of information
If peak detection is used to compress waveform data, then the compression ratio is improved, but low frequency information is obscured by high frequency signals
Solution Approach 1:
The patent segments the signal processing into separate pathways: one for peak detection and another for low-frequency component analysis. By dividing the processing tasks, the system can identify peaks without allowing high-frequency noise to dominate the low-frequency information extraction, thus preserving both types of information while achieving compression.
Solution Approach 2:
The patent introduces intermediary processing steps such as bandpass filtering and adaptive thresholding between peak detection and low-frequency analysis. These intermediary operations act as mediators that prevent high-frequency signals from obscuring low-frequency information during compression, allowing both to be preserved in the compressed representation.
3Speed
If very fast ADCs are used to capture high frequency signals in real time, then the sampling rate is improved, but the amount of data generated exceeds memory capacity
Solution Approach 1:
The patent applies preliminary compression and filtering operations to the high-speed ADC data before it is stored in memory. By performing pre-processing such as decimation, filtering, and feature extraction at the point of data generation, the system reduces the data volume that needs to be stored while maintaining the high sampling rate capability for accurate high-frequency capture.
Solution Approach 2:
The patent applies different quality levels and compression strategies to different portions of the data stream based on local signal characteristics. High-frequency segments with important information are preserved at higher quality with less compression, while quieter or less critical segments undergo more aggressive compression, thus managing overall data volume while maintaining sampling rate performance.
Data Source
AI summary
A waveform compression and display technique saves both a peak detected version (background version) and a decimated/lowpass filtered version (foreground version) of a sampled electrical signal. The two versions are displayed simultaneously overlaid together in a contrasting manner so as not to obscure information contained in either of them. The lowpass filtered version uses a series of simple lowpass filters with decimation to produce a single data stream from a plurality of data streams derived from the sampled electrical signal. The single data stream may then be subjected to additional filtering, such as a cascaded integrator-comb filter, to obtain a desired frequency bandwidth. When displayed, the peak detect pixels adjacent the decimated/lowpass filtered pixels may be adjusted in intensity so that the low frequency information of the lowpass filtered waveform is not lost, while the peak detect pixels further from the lowpass filtered pixels are intensified to highlight the high frequency information. Alternatively the background version intensity may be controlled by a user control over a first range from zero to a predetermined maximum, and the foreground version may be controlled over a second range from a default intensity to a maximum, saturated intensity.