Digital Moving Max Envelope Filter for Stable Trigger Waveforms
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Solution Overview
Problem
Current envelope filters in test and measurement instruments are typically implemented as analog circuitry, which can be inefficient and require smoothing to improve instrument operations.
Innovation Solution
Implementing a moving max filter as an envelope filter in test and measurement instruments, utilizing digital circuitry to detect the rising edge of a signal and produce a stable envelope width output, with selectable envelope width and the ability to switch between moving max and latched values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If analog circuitry is used to implement envelope filters, then the filter can be implemented with simple components (diode, resistor, capacitor), but the output waveform requires smoothing to improve instrument operations
Solution Approach 1:
The patent replaces the analog mechanical/electrical system (diode, resistor, capacitor circuit) with a digital system using an analog-to-digital converter, digital processor, and digital-to-analog converter. This substitution eliminates the need for smoothing circuitry and provides more reliable envelope detection through digital processing of the signal.
2Reliability
If digital circuitry is used to implement the moving max filter, then the envelope output becomes more stable and idealized, but the device complexity increases
Solution Approach 1:
The digital processor in the patent serves multiple functions: it converts the digital signal from the ADC, applies the moving max filter algorithm to generate the envelope, and can switch between different operating modes (moving max filter vs. latched values). This multi-functionality consolidates what would otherwise require separate circuits into a single versatile component.
3Adaptability or versatility
If the moving max filter uses a selectable envelope width, then the filter can adapt to different signal conditions, but the control complexity increases
Solution Approach 1:
The patent implements a dynamic envelope width parameter that can be adjusted based on signal characteristics and instrument settings. The digital processor dynamically adapts the filter window size to optimize performance for different signal conditions, frequencies, and amplitude modulations, providing versatility without requiring multiple fixed filter circuits.
Data Source
AI summary
A test and measurement instrument to receive a signal from a device under test, one or more analog-to-digital converters to receive the signal and convert the signal to digital samples, a moving max filter to receive the digital samples and produce a max value waveform from the digital samples within an envelope width to trigger operation of the test and measurement instrument, and one or more buffers to store max values from the digital samples. A moving max filter includes a max build-up circuit connected to one or more buffers to produce a building_up_max value, a max build-down circuit connected to the one or more buffers to determine which stored max values can be cleared from the one or more buffers and produce a building_down_max value, and a comparison block to find a maximum between the building_up_max value and the building_down_max value and to output the maximum.