Embedded DSP Spectrum Analyzer
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Embedded DSP Spectrum Analyzer
May 0104
April 25, 2001
Teradyne Corp
Julie DickersonBill Black
Prihamdhani Amran EERyan Butler CprEAaron Delaney EENicky Hilton CprE
Team Number:
Date:
Client:
Advisors:
Team Members:
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Presentation Outline
Introduction
Problem Statement
Design Objectives
End Product Description
Assumptions & Limitations
Risks and Concerns
Technical Approach
Project Success
Future Work
Human and Financial Budgets
Lessons Learned
Summary
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Introduction
Teradyne – very high end test equipment
Several Teradyne sponsored groupsGroup 1 – PC spectrum analyzerGroup 2 – Embedded DSP spectrum analyzerGroup 3 – Single board DSP spectrum analyzerGroup 4 – Replicating analyzers on single board
Purpose of projects – Replace ‘serial’ method of testing with faster ‘parallel’ approach
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Key ConceptsDynamic range
Ratio of signal levels expressed in dB
DSP - Digital signal processing
Fourier Transform – Translates signal from time domain to frequency domain
Notch filter - Rejects signals within a narrow band of frequencies and passes all other signals
Anti-aliasing filterA low-pass filter to prevent aliasing
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What is Aliasing?
Aliasing is the generation of a false (alias) frequency along with the correct one when doing frequency sampling.
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Dynamic Range
CD player: 96 dB
Tester must have dynamic range that is a factor of 10 better
Ratio V(tester) to V(cd player) = 10
20 * log(10) = 20 dB
Our tester – another factor of 10!!!
96 dB + 20 dB + 20 dB = 136 dB
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Fourier Transform
More than one signal present
Signal broken into frequency components
Time domain Frequency domain
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Problem Statement
Evaluate analog input signal between DC and 1MHz (bandwidth)
Process signal on external hardware
Display signal properties on PC
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Design ObjectivesDynamic range
Total dynamic range -135dBDigitizer -96 dBFilters approx. -40/50 dB
Signal propertiesMeasure five harmonicsMeasure THD, SNR, Noise floorMeasure amplitude of fundamental & harmonic frequenciesMeasure input frequencies from DC to 1MHz
Intended users and usesFuture Teradyne senior design teams
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End Product Description
External hardware
System componentsSignal generator
Filter board
A/D converter
Digital signal processor
Host computer
PC softwareGUI interface
DSP program
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Assumptions
Hardware selectionFinding A/D and DSP would be easy
Hardware integrationInterfacing A/D and DSP would be difficult
Software packageDevelopment tools for DSP available
Filter designHigh quality parts for filters available
Financial BudgetTeradyne will cover all costs
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Limitations
Technical knowledgeAnalog filter design
Limited experience with DSP
Hardware selectionReading data sheets
Available digitizer/DSP boards
SoftwareNo experience writing in Lab View
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Project Risks and Concerns
Hardware selectionDelay part orders
Delay system integration
Delay software development
Integrating hardwareFrying expensive equipment
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Technical Approach
Required specificationsExternal hardware approachTwin-T notch filtersAnalog Devices products
Design choices
HardwareCustom/commercial board design
Anti-aliasing filters
SoftwareLabView/C/C++/Java
E.A.G.L.E software
OrCAD p-spice
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Technical Approach
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Step 1 – Filtering
frequency by 40-50 dB
Filter board4 filters laid out on custom board
Anti-aliasingMakes sure no signals over1 MHz enter the system
Notch filtersKnocks down fundamental
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Notch Filter
Before notch filter After notch filter
Noise floorNoise floor
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Step 2 – A/D Conversion
Analog Devices 976A 16 bit
Signal from filter is digitized
Data passed to DSP
A/D channel determines which filter will be used.
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Step 3 – Signal Processing
Analog Devices DSP 40 MHz
Store digitized signal in DSP memory
Perform Fast Fourier Transform
Calculate signal properties of interest
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Step 4 – Calibration
Reduces total system error
Determines notch frequency of each filter
Calibration stepsGenerate white noise
Perform FFT
Find notch
Generate signal at notch frequency
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Notch Filter Calibration
White noise FFT of noise
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Step 5 – Display Data
DSP data sent to PC
Lists all signal properties of interest
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Evaluation of Project Success
Completed tasksFilter designFilter board designFilter board fabricationGUI code writtenDSP code written
Tasks not completedHardware integrationDSP and host PC communication code
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Future WorkHardware
Redesign to meet frequency specificationSingle board solution
FilteringMore filters addedPrefabricated filter banks
SoftwareRewrite DSP code for single board solutionOptimize algorithms for real time processing Add functionality to software
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Financial Budget
$0
$1,000
$2,000
$3,000
$4,000
$5,000
$6,000
$7,000
$8,000
$9,000
Actual $85 $248 $895 $0 $2,445 $3,673
Estimated $750 $200 $800 $2,000 $5,000 $8,750
Filter Poster Software A/D DSP Total
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Human Budget
0 Hours
100 Hours
200 Hours
300 Hours
400 Hours
500 Hours
600 Hours
700 Hours
800 Hours
900 Hours
Actual 81 Hours 89 Hours 188 Hours 106 Hours 464 Hours
Estimated 160 Hours 197 Hours 237 Hours 270 Hours 864 Hours
Amran Butler Delaney Hilton Total
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Lessons Learned
Keep ahead of deadlines
Make backup plansOrdering/Receiving partsSoftware problems
More documentationKeep better lab notesDocumentation for next team
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Closing Summary
Learned a lot about DSP and analog filter design
Team skills improvedUseful information passed to next group
AcknowledgementsTeradyneJulie Dickerson & Bill BlackBrian Nowak & Neeraj Nayak
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Questions