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Alias Protection (196)
Chapter Outline
Chapter 8 - Alias Protection (Digital Data Acquisition)
- Pyrotechnic Test Data Set Example—Alias-Protection
- Solution #1: Sample Really Fast
- Solution #2: Analog Anti-Alias Filters
- Filters
- The Basic Low-Pass-Filter Concept
- Brick-Wall vs. Real Filters
- How Filters Behave
- Aliasing Analysis
- Anti-Alias Filters … Hardware
- Complex Filter “Construction”
- Building a Filter
- Group Delay
- “Classical” Filter Types
- Bessel Filters
- Butterworth Filters
- Elliptical Filters
- Low-Pass Filter Comparison… Spectral Domain
- Filter Characteristic
- Filter/Sample-Rate
- Trade-Offs
- Aliasing…Revisited
- Aliasing Analysis—Assumption #1—Physical Considerations
- Pyrotechnic Test Data Set
- Assumption #2…Filter Cutoff Frequency
- Sampling Ratio Calculation
- The fR /fCR Ratio
- Performance of Different Filters
- Minimum Sampling Ratios for Different Filters
- The Aliasing Diagram—Filter/Alias Analyzer
- Anti-Alias Filter Effect (1.61 Points/Cycle)
- Removing Aliased Data
- How to Tell Whether a Data Set is Aliased
- “Digital” Anti-Alias Filters
- AC/DC Coupling
- Why do AC Coupling?
- AC-Coupling to Remove Offset
- AC-Coupling Methods
- Capacitive AC Coupling
- Offset Subtraction … Analog
- Offset Subtraction … “Digital”
- Recommendation
- The Downside of AC-Coupling
- AC-Coupling Distortion—More Examples