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EW Advanced Theory > Week 2 Theory > Flashcards

Week 2 Theory Flashcards

1
Q

What is frequency diveristy

A

When a radar transmits 2 or more frequencies simultaneously

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2
Q

What is frequency agility

A

When a radar switches between multiple frequencies in a controlled manner

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3
Q

Benifits of frequency agility

A

Good anti clutter
Eliminates second time round returns
Different material reflect different frequencies better than others

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4
Q

Benefits of continuous wave

A

Good for doppler
High average power
Narrow bandwidth

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5
Q

Disadvantages of continuous wave

A

Cant calculate range

Separate transmitter and receiver needed

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6
Q

What is frequency modulated continuous wave (FMCW)

A

Radar transmits continuously but changes freq over time

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7
Q

What is Interrupted continuous wave (ICW)

A

CW signal that gets interrupted not stopped so that the phase of the signal remains coherent

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8
Q

Types of inter pulse modulation

A

Stagger
Dwell and switch
Jitter
Agility

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9
Q

Types of stagger

A

Simple- seven or less

Complex- more than seven

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10
Q

What is switch and dwell

A

PRI is set for a number of pulses and then switches to a different freq for a number of pulses

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11
Q

Types of jitter

A

Discrete

Random

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12
Q

Firing order def

A

Order in which PRIs are transmitted

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13
Q

Element def

A

Describes an individual PRI

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14
Q

Positions def

A

Total number of PRIs in a cycle

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15
Q

Cycle length def

A

Time it takes to go through 1 sequence

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16
Q

Cycle rate def

A

Number of times a sequence is repeated in a second

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17
Q

Mean PRI def

A

Average of all positions in a cycle

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18
Q

What is UMOP

A

Unintentional modulation on pulse

Knows as SEI or fingerprinting

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19
Q

What is FMOP

A

Frequency modulation on pulse

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20
Q

What is FMOP used for

A

Varying frequency over the pulses length (sweep) allows for better range resolution

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21
Q

What is doppler

A

Apparent shift in frequency as an object moves towards or away from and observer

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22
Q

What is coherence

A

Continuity of phase from one signal to the next

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23
Q

What is doppler notch

A

When the velocity of a contact is bellow which a radar classes them as clutter and does not identify them

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24
Q

Tangental fade

A

Reducing of doppler due to a reduction in radial velocity

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25
Q

What is a pulse doppler range vs velocity

A 
Range ambiguous (blind range)
Velocity unambiguous
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26
Q

What is an MTI radars range vs velocity

A 
Range unambiguous
Velocity ambiguous (blind speed)
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27
Q

How does blind speed occur

A

When target is stationary
Or
Target has moved a whole number of wavelengths between pulses

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28
Q

How is blind speed solved

A

Raise PRF

Inter pulse modulation-if one freq misses another will hit

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29
Q

When does blind speeds occur

A

When doppler shift is equal to PRF or its harmonics

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30
Q

How are blind ranges resolved

A

Inter pulse modulation

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31
Q

Electrical components of a radar system

A

Oscillator
Mixer
Filter
Attenuator

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32
Q

Types of orbit

A

Circular

Eliptical

33
Q

Whats is the apogee

A

Max height min speed

34
Q

What is the perigee

A

Min height max speed

35
Q

Ad and dis of low earth orbit

A

Can be fixed
Decreased lag time

Need many satellites for full coverage

36
Q

Ad and dis of geostationary/geosychronus

A

Infinite dwell time
Doesn’t require a following antenna

High cost
Impossible to repair

37
Q

Ad and dis of sub synchronus

A

Fast coverage of large areas (up to 12 hour orbit)

Need many satellites for full coverage

38
Q

What is SEAD

A

Suppression of enemy air defence

Neutralise or degrade enemy defence
Enemies capability will remain

39
Q

What is DEAD

A

Destruction of enemy air defence

Permanently removes enemies capability
Destruction of a threat is generally preferable

40
Q

Triad of SEAD

A

C-130 compass call
EA-18 Growler
Anti radiation missiles

41
Q

What is a time sensitive target

A

Target that requires an immediate response

42
Q

What is the missile engagement process

A 
Search
Aquire
Track
Launch
Intercept
43
Q

What radar is used in the acquire phase

A

TA

44
Q

What radar is used in the track phase

A

TT

45
Q

What radar is used in the launch phase

A

TI
MG
fC

46
Q

Types of homing missile

A

Passive
Semi active
Active

47
Q

How does semi active missile work

A

Missile homes passively

Target is illuminated by launch platform

48
Q

How does passive missile work

A

Missile homes into transmissions emitted bu the target

Eg IR, RF, UV

49
Q

How does active missile work

A

Missile transmits and receives

Fire and forget

50
Q

What is command line of sight (CLOS)

A

Target and missile are tracked
Data link command one way to missile from ground station
Follows target

51
Q

What is command off line of sight

A

Target and missile are illuminated
Data link one way to missile
Target is intercepted

52
Q

What is track via missile

A

Target and missile are tracked
Missile also tracks target
Two way data link between missile and ground

53
Q

Properties of a Radar Warning Receiver (RWR)

A 
Sensitive
100% intercept
Covers wide range of freqs
360° azimuth
Accurate
De interleave signals
Display
54
Q

Types of RWR

A

Crystal video receiver (CVR)
Instantaneous frequency measurement receiver (IFM)
Superheterodyne receiver

55
Q

Properties of CVR

A

Covers a wide bandwidth
Simple and cheap

Cannot measure freqs
Cannot detect CW

56
Q

Properties of a IFM

A

Measures freqs
Simple

Cannot measure PRF or PW

57
Q

Properties of a SuperHet

A

Very sensitive and selective
Phase preserved so measures doppler

Needs to be programmed
Reliant on software to know what to look for

58
Q

What is MDD

A

Mission dependant data

Library of emitter parameters, scan strategies, maps etc

59
Q

Def of a countermeasure

A

Any action taken to negate a threat

60
Q

What are the three types of jamming

A

Spot
Barrage
Sweep

61
Q

What is radar burnthrough

A

As you get closer to the radar you are jamming returns get stronger and you are seen

62
Q

What is electronic repeater jamming

A

Takes a signal and sends it out with a time delay

63
Q

What is false target generation

A

Time delay retransmits position forward and back

Retransmit into side-lobes to change position left and right

64
Q

Types of active decoys

A

Towed radar decoy

Expendable active decoy

65
Q

Types of passive decoy

A

Chaff

Cut to half wavelength of the signal you want to jam

66
Q

How to create stealth

A

Reduction of radar cross section
Reflectivity of materials
Shape-lumps bumps and cavities

67
Q

What does a missile warning system (MWS) detect

A

Radar cross section and movement
Mussel flash
Motor ignition
Motor plume

68
Q

Types of MWS

A

Radar MWS
IR MWS
UV MWS
Laser MWS

69
Q

Properties of a flare

A

High peak intensity
Fast rise time
Long burn time
Credible signature

70
Q

How to counter a dual band detector

A

Spectral flares

71
Q

How to counter kinematic flare rejection

A

Aerodynamic flares

72
Q

What is an IRCM

A

Multi directional IR jammer

73
Q

What is a DiRCM

A

Focuses energy in a beam for better range and to blind the missile

74
Q

What does a low probability of intercept (LPI) radar do

A

Reduces possibility of an enemy spotting a radar

75
Q

3 types of LPI radar

A

LPID-low prob of identification
LPI- low prob of intercept
Quiet radar

76
Q

Properties of Secondary surveillance radar

A

Greater range
Less power needed
Coded info

Requires aircraft to have transponder to interrogate

77
Q

What is fruiting

A

False replies unsynchronised in time

SSR transmit and receive on same freq so could get unwanted reply

78
Q

What is garbling

A

When two aircraft are similar in range and/or azimuth within 3.2nm, signal gets mixed up

EW Advanced Theory (3 decks)

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