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High Speed Data Measurer for use
with Quantum Cryptography and
Laser Range Detector
By
Michael Noone
KanKan YuCharles Ruiz
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Outline
Introduction
Objective
Applications
Technology
Cost Analysis
Conclusion Q & A
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Introduction
High Speed Data Measurer used as a
component for a Laser Range Finder and
Quantum Random Number Generator.
Combination of high speed circuit design,
optics, and control logic to produce a Laser
Range Finder.
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Applications
High Speed Data Measurer
Laser Range Finder
Quantum Random Number Generator
Laser Range Finder
Computer Imaging Systems
Single use distance detector
Random Number Generator
For use with Quantum Cryptography
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Objectives
Design and build a high speed timing circuit Must find the time between rising edges of pulses
Accurate to approximately 50ps
Interface timing circuit to computer
Write control software to interpret data from timing circuit Design and build laser range finder using timing circuit
Use time of flight range finding technique
Use high speed laser driver
Use high speed receiver Receiver should filter out all wavelengths except for that of the laser used
Design and build a scanning mechanism that rotates the laserrangefinder skill in one or two axes
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Technology
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Project Construction
Cadsofts Eagle for schematic design and PC board layout
Advanced Circuits and ECE shop for board layout
Parts ordered from: Transducers Direct (timer chips)
Digi-Key Mouser
Newark
ECE shop
Professor Kwiat
Circuit boards hand soldered Hakko 936-12 ESD safe iron
Kester no clean flux pen
Kester no clean solder
fine tweezers for component placement
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In a nutshell
Timing
Circuit
Detector
Circuit
ScanningMechanism
Control
Module
Laser OpticsLaser Driver
Circuit
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Laser Driver Objective & Parameters
Objective
Drive the Laser Diode with crisp square pulses
Parameters High Speed Data In
Quick Rise and Fall Time
Drive 90 mA for Laser Diode
Low Noise
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Laser Driver CircuitConcept Art
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Board Layout
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Final Product
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Transmit Optics (Complete)
Requirements: Collimated beam
Optimum power match up with laser driver
Wavelength matching up with receiveroptics
Fast rise time
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Receiver Optics (Incomplete)
Requirements:
Detection of scattered beamfrom objectand discrimination of ambient light.
Accurate and constant time spent onsending signal to timing circuit.
Fast rise and fall times that allow for higher
precision in laser range finder.
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Optics Results
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Timing Circuit Objectives
Circuit that can measure time lapsed between rising edges oftwo pulses
To be used for measuring time of flight of laser pulses Measure the time span between outgoing laser pulse and incoming
received laser pulse Goal is 1cm resolution
For quantum cryptography random number generator: Needs to measure time span between pulses all on the same line
Needs approximately 200ps resolution.
Needs to be ready for a new sample within about 20ns of receivingprevious sample
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Resolution
For Laser scanning circuit, we want 1cm resolution
Speed of light is 299792458 m/s
Thus, we theoretically need resolution of .01 * 2 *
299792458 m/s = 67ps This makes assumption all other components are perfect
Since all components are not perfectwe need better than 67ps
resolution
For Prof. Kwiats quantum cryptography circuit, weneed about 200 ps resolution, so this easily falls
within laser range finder design parameters
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Timing Circuit Considered
Discrete timing circuit
Acam TDC-GP2
Acam TDC-GPX
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Discrete Timing Circuit
Start signal latched D-latch so that mosfet turns on,charging C through an RC circuit
Stop signal un-latches D-latch so that mosfet turns
off, stopping the charging of C ADC then reads in voltage across capacitor, and then
can find amount of time spent charging capacitor byextrapolating it from Vc = 5 * (1-e^(t/(RC) ) )
Unfortunately, propagation delay and gatecapacitances of components completely destroysaccuracy and resolution of such a circuit
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Discrete Timer Schematic
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Acam TDC-GP2
Special purpose timing chip designed to measure the amountof time that elapsed between a start pulse and a stop pulse
Somewhat low cost - $28/chip
50 ps resolution
Very small QFN 32 package
Fairly simple external components needed
SPI interface Runs at up to 25MHz
Would take approximately 1s to read out data Fast enough for laser range finder
Too slow for random number generator
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Acam TDC-GPX
Special purpose timing chip designed to measure theamount of time that elapsed between a start pulse anda stop pulse
High cost - $187/chip 10 ps resolution
100 TQFP package
Very complicated external components needed
High speed parallel interface Easily fast enough for both random number generator and
laser range finder
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Final Decision
Our choice:
We chose to use the Acam TDC-GPX
Though the other two circuits considered would have been
considerably easier to design, build, and debug, this wasthe only way for us to meet Prof. Kwiats needs
Parameters for TDC-GPX schematic design:
Ultra clean power supply
Minimal part count
Parts with small footprints
Singled ended and differential start and stop signals
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Final schematic:
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Parameters for TDC-GPX board design
Maximize size and integrity of ground plane
Minimize noise on signal traces
Minimize all trace lengths, especially signaland analog traces
Traces that have to cross over each other
should be perpendicular
Match impedances and trace lengths of
differential signals
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Final board design
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Final board top
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Final board bottom
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Final PCB Top
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Final PCB Bottom
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Control Module (Complete)
Requirements: Provide successful start up
of laser driver and TDC-
GPX.
Provide successfulinteraction between the
laser driver and the TDC-
GPX.
Program onto a Spartan-3
for this interaction
Serial communication with
computer to send timing
information.
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Control Module -- Timing Circuit Pseudo
Code &Laser Driver State Diagram
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Laser Driver State Machine
High State
Bump Edge Counter (Rising)
Low State
Bump Edge Counter (Falling) 10 Pulses sent stage
00 Error Code Fail State
Laser Shutdown State
TriggerLaser
Process Data
Start Over
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Control Module Results
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Cost AnalysisSoftware (COCOMO)Effort Adjustment Factor (EAF) Rating : 1.14
Organic Software Project
Coefficient a = 2.4
Exponent b = 1.05
Size of software = 6 K Lines of Code
Effort = [ a (Size)b ] (EAF) = 17.95 person-months Software Development time = Effort/people = 4.49 months
4.49 months * (60 hours/month labor) ($ 60 / hour) (3 people)
Labor Cost = $ 48.5K
Without Makelas proposed 2.5 estimation factor
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Cost AnalysisHardware Costs and
Labor Parts Cost : $377.33
Basic Electronic Components (Resistors, Capacitors, etc) - $35.00
TDX-GPX - $187.00
Vertical SMA Connector$5.94 Circuit Board - $33.00
Photodiode - $6.14
Laser Diode - $5.00
Spartan 3 FPGA - $100.00
AND 2870 - $5.25 Hardware Labor Costs and Estimation
(160 hours) ( $60/hour) (3 people)
Labor = $28.8K
Total Costs = Software Labor + Hardware Labor + Parts = $77677.33
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Success consists of going from
failure to failure without loss ofenthusiasm.
-- Winston Churchill
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Successes
Laser Driver Circuit Design and Layout
Transmit Optics
Timing Circuit
Control Module
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Shortcomings Laser Driver Circuit
High Speed Circuit
Extremely Sensitive
Receiver Optics
Breadth of work needed to build a proper receiver circuit
was underestimated. Misrecognition of primary task.
Failure to identify primary task within time frame to allowsuccessful completion of this portion of the project.
Timing Circuit
Complex Circuit Research
Complex Board Layout
High Speed Circuit
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Special Thanks
Special thanks goes to:
Professor Kwiat
Evan Jeffrey
Mark Smart
Dr. Peter Dragic
Dr. Stephen Bishop
Michael Zhang
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Question and Answer