dsp analysis of digital vector slope gauge data produced

DSP Analysis ofDSP Analysis ofDigital Vector Slope Gauge DataDigital Vector Slope Gauge Data

Produced byProduced by

Ocean Wave SimulationOcean Wave Simulation

EECS 803 EECS 803 -- Introduction to ResearchIntroduction to ResearchProf. Earl Prof. Earl SchweppeSchweppe, Instructor, Instructor

Evan L. Bryson 618093Evan L. Bryson 618093

OverviewOverview

•• Ocean Wave BehaviorOcean Wave Behavior•• The Vector Slope Gauge (VSG)The Vector Slope Gauge (VSG)

–– VSG HistoryVSG History–– VSG FunctionVSG Function

•• Ocean Wave Data SimulationOcean Wave Data Simulation•• OffOff--line Processingline Processing•• Future WorkFuture Work

Ocean Wave BehaviorOcean Wave Behavior

•• SpectrumSpectrum•• Wavelength, period, and velocityWavelength, period, and velocity•• Deep water vs. shallow water wavesDeep water vs. shallow water waves•• Sea = linear sum of wavesSea = linear sum of waves•• Orbital velocityOrbital velocity

Ocean Wave SpectrumOcean Wave Spectrum

(From Kampion, 1997)

Wave Velocity vs. Wavelength and PeriodWave Velocity vs. Wavelength and Period


Simple Simple WavefrontWavefront DescriptionDescription

phase directionapproach wave

(sec) period wave T (m)th waveleng L

(rad/m)number wave L

2

(rad/sec)frequency angular T2 where

) sin cos cos( ),,(:position and at time ocean wave ofHeight

====

==

==Ω

+++Ω=

φα

πκ

πφακακ yxtAtyxh

(x,y)t

Superposition of WavesSuperposition of Waves

•• Complex Sea = Superposition of Complex Sea = Superposition of many many wavefrontswavefronts

•• Individual Individual wavefrontswavefronts are are approximately sinusoidal in deep approximately sinusoidal in deep oceanocean

•• WavefrontsWavefronts change shape near change shape near shore as water depth decreasesshore as water depth decreases

•• Single Single wavefrontwavefront is rare in natureis rare in nature•• WavefrontsWavefronts are initiated by winds are initiated by winds

over the ocean at other locationsover the ocean at other locations

(From Bascom, 1964)

Orbital VelocityOrbital Velocity


(From Bascom, 1964)

OverviewOverview




VSG HistoryVSG History

•• Version 1 Version 1 –– Analog VSGAnalog VSG–– Tested in the North Sea in 1990Tested in the North Sea in 1990

•• Version 2 Version 2 –– Improvement of Version 1Improvement of Version 1–– Tested at Duck Pier in 1995Tested at Duck Pier in 1995

•• Version 3 Version 3 –– Digital VSGDigital VSG–– No ocean surface data availableNo ocean surface data available

VSG FunctionVSG Function

x

y

VSG

z

y axis is radar look directionΘ is incidence angleH is height above mean

ocean surface

H

Θ

Typical VSG Beam Pattern on Ocean SurfaceTypical VSG Beam Pattern on Ocean Surface

Beam 3

Beam 2

Beam 1

~ 1 meter

~ 1 meter

Frequency Format of VSG Radar SignalFrequency Format of VSG Radar Signal

F

T

Cycle

Sweep

Up-sweep

Down-sweep

Beam 1 Beam 2 Beam 3

Bandw

idth

Instantaneous IF Output and ReturnInstantaneous IF Output and Returnfor Range Measurementfor Range Measurement

Transmitted Signal Returned Signal

F

T

Radar Signals

Intermediate Frequency Signal (Difference Frequency)

(Adapted from Ulaby, Moore, and Fung, Fig. 7.25, p. 513)

Instantaneous IF Output and Return Instantaneous IF Output and Return for Range and Doppler Measurementfor Range and Doppler Measurement

Transmitted Signal Returned Signal

F

T

Radar Signals

Intermediate Frequency Signal (Difference Frequency)


Instantaneous Frequencies for Point TargetInstantaneous Frequencies for Point Target

Transmitted Signal

Returned SignalF

T

Magnified View of a Portion of the Signal

∆F

∆T


VSG ParametersVSG Parameters

•• RangeRange•• Sweep repetition Sweep repetition

frequencyfrequency•• Single (Up or Down) Single (Up or Down)

sweep timesweep time•• Sweep rateSweep rate•• Minimum DSP sample Minimum DSP sample

rateMHz 1.0 1.12

sec / Mhz 4.76 126600

µs126 21

Hz 4000 )14.14104(600

10)45010(3 4

m 14.14 )45cos(

10 cos

min

6

38

=⋅⋅=

===

≅=

≅⋅

⋅⋅=

⋅⋅

=

===

IFs

sweep

Bsweep

IFB

VSG

ff

TB

∆t∆f

fT

RBfcf

hR

µ

θ

rate

OverviewOverview




Ocean Wave Data SimulationOcean Wave Data Simulationfor Digital VSGfor Digital VSG

•• Characterize simple ocean surfacesCharacterize simple ocean surfaces–– Flat surface (calm sea)Flat surface (calm sea)–– Single Single wavefrontwavefront–– Multiple wave frontsMultiple wave fronts

•• Add Doppler shift to surfacesAdd Doppler shift to surfaces•• Convert ranges + Doppler to frequenciesConvert ranges + Doppler to frequencies•• Digital sampling of frequenciesDigital sampling of frequencies•• Scale and shiftScale and shift•• Convert to 12Convert to 12--bit unsigned integersbit unsigned integers•• Create data files in digital VSG format Create data files in digital VSG format

Ocean Wave Data SimulationOcean Wave Data SimulationWaveSim7.mWaveSim7.m

VSG Parameters

Ocean WaveParameters

Wavesim7.m

RangeEst.m

NsPerSweep.m

SampGen.m

Save2Slopes.m

slopeab2.m

slopepoimod.mslrangemod.m

SlopeOut.txt

Range IF SampledIF

VSGOutput.m

VSGOut.bin

Digital VSG Data FormatDigital VSG Data FormatMSB LSB

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

not used (always 0)

Beam

#

Up/D

own

Data

12 bit unsigned integer

00 = Beam 101 = Beam 210 = Beam 311 not used

0 = Up1 = Down

OverviewOverview




OffOff--line Processingline ProcessingCurrent Vector Slope Gauge Concept

Data StorageHard Disk

Raw VSGData

Data Processingand Calculations

DataPreparation

Printer Outputof Results

Delay

VSG

DSP Algorithm DSP Algorithm –– Ocean ProjectOcean Project

PSD StorageBuffer

Calculatefeff, u

BPFDataBeam 1 Up

Calculatefavg, u

Scale toVelocity

Scale toRange

Calculatefeff, d

StorageBuffer

Calculatefavg, d

PSD BPFDataBeam 1 Down

1

fd1

R1

+

_

+

+

PSD StorageBuffer

Calculatefeff, u

BPFDataBeam 2 Up

Calculatefavg, u

Scale toVelocity

Scale toRange

Calculatefeff, d

StorageBuffer

Calculatefavg, d


2

fd2

R2

+

_

+

+

PSD StorageBuffer

Calculatefeff, u

BPFDataBeam 3 Up

Calculatefavg, u

Scale toVelocity

Scale toRange

Calculatefeff, d

StorageBuffer

Calculatefavg, d


3

fd3

R3

+

_

+

+

CalculateVectorSlope

Calculatefd, avg

R1 R2 R3

fd1 fd2 fd3

LookAngle

Adapted from DSP Algorithm for Ocean Radar Project, Gary W. Hamilton II

DSP of Stored Ocean Wave DataDSP of Stored Ocean Wave DataDSP2.mDSP2.m

VSG Parameters

VSGOut.bin

GetTimeSeries2.m

DSP2.m

FindPSD.m

evanslope.m

Upsweep

FindEffFreq.m

SumAverage

Frequency

Downsweep

DifferenceAverage

Frequency

Range DopplerSlopesSx, Sy

Shift and Scale

OverviewOverview




Future WorkFuture Work

•• Collect ocean data on digital VSGCollect ocean data on digital VSG•• Comparison to Duck Pier resultsComparison to Duck Pier results•• Orbital velocity measurementOrbital velocity measurement•• RealReal--time DSPtime DSP•• Adaptation to shipboard environmentAdaptation to shipboard environment

RealReal--Time Vector Slope Gauge ConceptTime Vector Slope Gauge Concept

On-ScreenResults

VSG

Raw VSGData DSP Board

DSP Program

dsp analysis of digital vector slope gauge data produced

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