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EW Advanced Theory > Week 2 Theory > Flashcards

Week 2 Theory Flashcards

(78 cards)

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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
What is a pulse doppler range vs velocity
``` Range ambiguous (blind range) Velocity unambiguous ```
26
What is an MTI radars range vs velocity
``` Range unambiguous Velocity ambiguous (blind speed) ```
27
How does blind speed occur
When target is stationary Or Target has moved a whole number of wavelengths between pulses
28
How is blind speed solved
Raise PRF | Inter pulse modulation-if one freq misses another will hit
29
When does blind speeds occur
When doppler shift is equal to PRF or its harmonics
30
How are blind ranges resolved
Inter pulse modulation
31
Electrical components of a radar system
Oscillator Mixer Filter Attenuator
32
Types of orbit
Circular | Eliptical
33
Whats is the apogee
Max height min speed
34
What is the perigee
Min height max speed
35
Ad and dis of low earth orbit
Can be fixed Decreased lag time Need many satellites for full coverage
36
Ad and dis of geostationary/geosychronus
Infinite dwell time Doesn’t require a following antenna High cost Impossible to repair
37
Ad and dis of sub synchronus
Fast coverage of large areas (up to 12 hour orbit) Need many satellites for full coverage
38
What is SEAD
Suppression of enemy air defence Neutralise or degrade enemy defence Enemies capability will remain
39
What is DEAD
Destruction of enemy air defence Permanently removes enemies capability Destruction of a threat is generally preferable
40
Triad of SEAD
C-130 compass call EA-18 Growler Anti radiation missiles
41
What is a time sensitive target
Target that requires an immediate response
42
What is the missile engagement process
``` Search Aquire Track Launch Intercept ```
43
What radar is used in the acquire phase
TA
44
What radar is used in the track phase
TT
45
What radar is used in the launch phase
TI MG fC
46
Types of homing missile
Passive Semi active Active
47
How does semi active missile work
Missile homes passively | Target is illuminated by launch platform
48
How does passive missile work
Missile homes into transmissions emitted bu the target | Eg IR, RF, UV
49
How does active missile work
Missile transmits and receives | Fire and forget
50
What is command line of sight (CLOS)
Target and missile are tracked Data link command one way to missile from ground station Follows target
51
What is command off line of sight
Target and missile are illuminated Data link one way to missile Target is intercepted
52
What is track via missile
Target and missile are tracked Missile also tracks target Two way data link between missile and ground
53
Properties of a Radar Warning Receiver (RWR)
``` Sensitive 100% intercept Covers wide range of freqs 360° azimuth Accurate De interleave signals Display ```
54
Types of RWR
Crystal video receiver (CVR) Instantaneous frequency measurement receiver (IFM) Superheterodyne receiver
55
Properties of CVR
Covers a wide bandwidth Simple and cheap Cannot measure freqs Cannot detect CW
56
Properties of a IFM
Measures freqs Simple Cannot measure PRF or PW
57
Properties of a SuperHet
Very sensitive and selective Phase preserved so measures doppler Needs to be programmed Reliant on software to know what to look for
58
What is MDD
Mission dependant data Library of emitter parameters, scan strategies, maps etc
59
Def of a countermeasure
Any action taken to negate a threat
60
What are the three types of jamming
Spot Barrage Sweep
61
What is radar burnthrough
As you get closer to the radar you are jamming returns get stronger and you are seen
62
What is electronic repeater jamming
Takes a signal and sends it out with a time delay
63
What is false target generation
Time delay retransmits position forward and back | Retransmit into side-lobes to change position left and right
64
Types of active decoys
Towed radar decoy | Expendable active decoy
65
Types of passive decoy
Chaff | Cut to half wavelength of the signal you want to jam
66
How to create stealth
Reduction of radar cross section Reflectivity of materials Shape-lumps bumps and cavities
67
What does a missile warning system (MWS) detect
Radar cross section and movement Mussel flash Motor ignition Motor plume
68
Types of MWS
Radar MWS IR MWS UV MWS Laser MWS
69
Properties of a flare
High peak intensity Fast rise time Long burn time Credible signature
70
How to counter a dual band detector
Spectral flares
71
How to counter kinematic flare rejection
Aerodynamic flares
72
What is an IRCM
Multi directional IR jammer
73
What is a DiRCM
Focuses energy in a beam for better range and to blind the missile
74
What does a low probability of intercept (LPI) radar do
Reduces possibility of an enemy spotting a radar
75
3 types of LPI radar
LPID-low prob of identification LPI- low prob of intercept Quiet radar
76
Properties of Secondary surveillance radar
Greater range Less power needed Coded info Requires aircraft to have transponder to interrogate
77
What is fruiting
False replies unsynchronised in time SSR transmit and receive on same freq so could get unwanted reply
78
What is garbling
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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