fundamentos de energía

8/6/2019 Fundamentos de energía

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Naval Weapons Systems Naval Weapons Systems

Energy FundamentalsEnergy Fundamentals



Learning Objectives Learning Objectives

Comprehend the basic application of Comprehend the basic application of electronic systems and electromagneticelectronic systems and electromagneticwave theory to applications in radars,wave theory to applications in radars,communications, and radio navigationcommunications, and radio navigationsystems.systems.

Comprehend radar and radio waveComprehend radar and radio waveparameters.parameters.




Know and be able to apply radar andKnow and be able to apply radar andradio wave theory (Maxwell·s Theory;radio wave theory (Maxwell·s Theory;wl,f ,v relationship)wl,f ,v relationship)

Comprehend the basic operation of aComprehend the basic operation of asimple radar/ radio systemsimple radar/ radio system

Comprehend the concepts of time andComprehend the concepts of time anddistance as they affect wave phase angledistance as they affect wave phase angleand interference.and interference.




Know basic electromagnetic interferenceKnow basic electromagnetic interferencefactors in ship and weapons designfactors in ship and weapons design

Know electromagnetic wave propagationKnow electromagnetic wave propagation(reflection, refraction, diffraction, and(reflection, refraction, diffraction, andducting)ducting)

Define: ground plane, free space, reDefine: ground plane, free space, re--radiation, sky wave, space wave, groundradiation, sky wave, space wave, groundwaves, and troposphere waves.waves, and troposphere waves.



Energy Fundamentals Energy Fundamentals

One important weapon systemOne important weapon systemrequirements is the ability to detectrequirements is the ability to detect

targets.targets.Detection accomplished throughDetection accomplished through

exploiting the electromagneticexploiting the electromagnetic

spectrumspectrumElectromagnetic energy comes in manyElectromagnetic energy comes in manyforms: RADAR, Micro /Radio waves,forms: RADAR, Micro /Radio waves,IR, Light, Sound...IR, Light, Sound...




OverviewOverviewRADARRADAR

Electromagnetic (EElectromagnetic (E--M)WaveM)Wave

CharacteristicsCharacteristics

Maxwell·s TheoryMaxwell·s Theory

PolarizationPolarization

InterferenceInterference

Propagation of EPropagation of E--M wavesM waves

Transmission Range factorsTransmission Range factors




RADAR RADAR RARAdio dio DDetectionetection AAndnd RRanging anging

Radar is anRadar is an electromagnetic waveelectromagnetic wave that acts like anythat acts like anyother electromagnetic wave (i.e.other electromagnetic wave (i.e. -- radio , light, etc.)radio , light, etc.)

Characteristics of a radio wave assuming aCharacteristics of a radio wave assuming afrequency of 2 Hertz:frequency of 2 Hertz:

Cycle

Amplitude

1 second



T raveling WaveT raveling Wave

CharacteristicsCharacteristicsFrequencyFrequencyMeasuredMeasured

in Hertz (Hz)in Hertz (Hz)

(Cycles/sec)(Cycles/sec)

Wavelength = Speed of Light / Wavelength = Speed of Light / FrequencyFrequency




CharacteristicsCharacteristicsPeriodPeriodThe time requiredThe time required

for a full cyclefor a full cycle

Inverse of FrequencyInverse of Frequency

T=1/ fT=1/ f

T




CharacteristicsCharacteristics Wavelength Wavelength

The distanceThe distance

between 2 identicalbetween 2 identical

points on adjacentpoints on adjacent

waveswaves




CharacteristicsCharacteristicsCoherencyCoherency

A wave that is pureA wave that is pure

Sinusoid and aSinusoid and a

singular frequencysingular frequency

AdvantagesAdvantages::--Doppler shift canDoppler shift can

be measured.be measured.

--Better signal to noise ratio.Better signal to noise ratio.

CoherentCoherent

No

nNo

n--Co

herentCo

herent




CharacteristicsCharacteristicsVelocityVelocity

The speed of lightThe speed of light

AmplitudeAmplitude

Distance from theDistance from the

baseline to the crest of the wavebaseline to the crest of the wave



M axwell·s T heory M axwell·s T heory

An accelerating electric field willAn accelerating electric field willgenerate a timegenerate a time--varying magneticvarying magnetic

field.field.

A timeA time--varying magnetic field willvarying magnetic field will

generate a timegenerate a time--varying electric field.varying electric field.

...and so on...and so on...and so on......and so on...and so on...and so on...



Generation of Electromagnetic RadiationGeneration of Electromagnetic Radiation

+

-

+

-

-

+

a b c d

= Alternating Current

Source



Formation of Electric and M agnetic Formation of Electric and M agnetic

Fields around an Antenna Fields around an Antenna

e- e- e-

E-line

Mag field

Electric field _|_ Magnetic Field _|_ Direction ofPropagation.



End of Part 1 End of Part 1

Questions ?Questions ?



Energy Energy

Fundamentals FundamentalsPart IIPart II



Wave Pro

pagatio

n Wave Pro

pagatio

n Wave Types Wave Types



What is Polarization?What is Polarization?

TheThe directiondirection of polarization of of polarization of an antenna is defined as thean antenna is defined as the

electric field vectorelectric field vector..



I nterference I nterference

Electromagnetic wave interference canElectromagnetic wave interference canbe bothbe both

²² ConstructiveConstructiveNet field strength > Individual fieldNet field strength > Individual field

²² DestructiveDestructive

Net field strength < Individual fieldNet field strength < Individual field

Interference varies with phase angleInterference varies with phase angle



Constructive I nterferenceConstructive I nterference

Constructive InterferenceConstructive Interference



Constructive I nterferenceConstructive I nterference

Destructive InterferenceDestructive Interference



Propagation Paths of E Propagation Paths of E--M M

WavesWavesReflectionReflection

RefractionRefractionDiffractionDiffraction



... Reflection...... Reflection...

Incident WaveReflected Wave

Surface type plays a role in the amount of Surface type plays a role in the amount of energy reflectedenergy reflected

Angle of incidence = Angle of reflectedAngle of incidence = Angle of reflectedwave.wave.



... Refraction...... Refraction...

-- Incident wave passes through two Incident wave passes through two transparent media in which thetransparent media in which thevelocity of light differs...velocity of light differs...

-- Incident wave divides into a Incident wave divides into areflected wave and a refracted wave.reflected wave and a refracted wave.



... Diffraction...... Diffraction...

island

notdetected

detected

...plane waves traveling in a straight...plane waves traveling in a straightpath bend around a boundary orpath bend around a boundary oro

bstructio

n.o

bstructio

n.



Wave PropagationWave Propagation --relationship between distancerelationship between distance

and frequencyand frequency

G

round WavesG

round WavesSky WavesSky Waves

Space WavesSpace Waves



Ground Wave...Ground Wave...

Very low frequenciesVery low frequencies

Vertical polarizationVertical polarization

Waves travel along earth·s surface. Waves travel along earth·s surface.

55--10Khz10Khz

Very l

ong wavelengths

Very l

ong wavelengths -- unsuitableunsuitablefor ships & aircraft, except commsfor ships & aircraft, except comms

ShoreShore--based installations (HFbased installations (HF--DF)DF)



Sky Wave...Sky Wave...

EE--M energy refracts back towards theM energy refracts back towards theearth·s surface in upper ionosphereearth·s surface in upper ionospherelayer.layer.

EE--M energy then reflects back towardM energy then reflects back towardupper layer again.upper layer again.

Frequencies used up to 550 KHzFrequencies used up to 550 KHz

effectivelyeffectively Wavelengths still too long for Wavelengths still too long for

anything but comms by aircraft andanything but comms by aircraft and

ships.ships.



Space Wave...Space Wave...

Above 30 MHz, ionosphere will notAbove 30 MHz, ionosphere will notrefract Erefract E--M waves back toward earth.M waves back toward earth.

Energy tends to travel in straight line.Energy tends to travel in straight line.



Ducting ... Ducting ...

Phenomenon which enhances thePhenomenon which enhances therange of electromagnetic waves.range of electromagnetic waves.

Usually occurs w/temperatureUsually occurs w/temperatureinversion.inversion.

Cold AirCold Air

Warm Air Warm Air

Cold AirCold Air



T ransmission LossesT ransmission Losses

Spreading: Energy per unitSpreading: Energy per unit

area pro

po

rtio

nal to

1/R.area pro

po

rtio

nal to

1/R.Absorption: Molecules of Absorption: Molecules of

medium absorb some of themedium absorb some of the

energy as it passes through.energy as it passes through.

22



SummarySummary

RADARRADAR

Electromagnetic (EElectromagnetic (E--M)WaveM)WaveCharacteristicsCharacteristics

Maxwell·s TheoryMaxwell·s Theory



Propagation of EPropagation of E--M wavesM waves

Transmission Range factorsTransmission Range factors



Questions ?Questions ?



Assignment: Assignment:

ReadRead

Chapter 2Chapter 2

Radar Principles and SystemsRadar Principles and Systems

fundamentos de energía

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