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Day 1 Flashcards

1
Q

What is the doppler effect (verbatim)

A

An apparent shift in observed frequency of waveform due to difference in velocity of object relative to observer.

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2
Q

Explain what happens with doppler when moving towards, away and at 90 degrees to the observer

A

Moving towards = increase in frequency
Moving away = decrease in frequency
90 degrees = no change in frequency

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3
Q

What is the coherent definition?

A

Consistent or continuity in phase of signal from one pulse to the next

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4
Q

What are the requirements for a doppler radar? 2

A

Coherent radar

Receiver must be linked to TX to know phase

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5
Q

Explain tangential fade

A

As a target moves away from the observer, the doppler effect will decrease. Makes it hard to distinguish contact over clutter until the contact fades out as the relative direction approaches a tangent to the observer.

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6
Q

Explain doppler notch

A

Any moving objects under a set velocity threshold will be classed by the radar as clutter and will not display them. Anything below the speed is considering in doppler notch.

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7
Q

What is the main limitation of continuous wave on airborne platforms and what is the solution?

A

Weight & two antennas required.

Solution: interrupted continuous wave radar.

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8
Q

What types of radar use pulse doppler?

A

Target tracking

Airborne intercept

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9
Q

How does a pulse doppler radar work?

A

Measures targets radial velocity by measuring phase shift of return pulse, comparing the phase to originally transmitted pulse.

Separates moving targets from stationary clutter

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10
Q

How does an MTI radar work?

A

Detects moving targets against stationary background clutter and and filters out those with no doppler shift.

Displays range and bearing on a PPI display often used by ATC.

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11
Q

MTI vs Pulse doppler table

A

PRF Range Velocity
MTI Low Unambiguous Ambiguous (Blind speeds)
Pulse Doppler High Ambiguous (blind ranges) Unambiguous

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12
Q

What are blind speeds?

A

Blind speeds occur on a coherent radar when the doppler shift of a returning pulse is equal to the PRF of its harmonics.

Can be defeated by increasing the PRF or altering the PRF on a pulse to pulse basis ie inter pulse modulation.

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13
Q

What are blind ranges and how can they be defeated?

A

Occurs at ranges where a radar receives a returning transmission when the radar is set to transmit not receive. Occurs at increments of MUR and size dictated by pulse width.

Defeated by decreasing PRF or altering the PRF on a pulse to pulse basis ie interpulse modulation.

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14
Q

Explain purpose and function of an amplifier

A

Converts low power radio freq to a high power signal.

—–►——

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15
Q

Explain purpose and function of the Oscillator

A

Generates sinusoidal signal to enable conversion of IF to RF and RF to IF. Generally non coherent

—⍬—

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16
Q

Explain the purpose and function of a mixer

A

The mixer produces the sum and difference of the modulated signal and local oscillated output

—-⦻—-
|

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17
Q

Explain purpose and function of the filter

A

Removes unwanted frequencies

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18
Q

List the types of filters (4)

A

High pass
Low pass
Band pass
Notch

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19
Q

Explain purpose and function of the attenuator

A

Prevents high signal levels from overloading the mixer

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20
Q

Explain the need for satcom

A

Long distance communications
Continuing growth in digital transmission
Usable in remote areas
HQs and commanders in different countries

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21
Q

What range does SATCOM frequency use? What are the limitations?

A

240mhz - 32ghz

<1ghz cosmic noise
>15ghz atmospheric attenuation, noise & depolarisation

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22
Q

What bands do NATO use for SATCOM and why (4)

A

UHF, SHF and EHF

Why: limited rain fade
High link availability
High data rate volumes
Terminal size suitable for deployed and remote locations

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23
Q

What are the advantages and disadvantages of military satcom? 4 + 4

A

Jam resistant
Secure encryption
Reserved bandwidth for gov
Available in remote regions

Cost
Congestion of frequencies
Coverage is orbit dependant
Interference and propagation

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24
Q

List the 6 satellite sub systems

A 
Transponders
Antennae
Telemetry and command
Attitude and orbit control
Propulsion
Electrical power
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25
Q

What are the two types of satellite orbit? And what 3 planes

A

Circular and elliptical

Equatorial, polar or inclined planes

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26
Q

Explain circular orbit

A

No orbit is perfectly circular but have eccentricity of 0 degrees.

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27
Q

Explain elliptical orbit

A

Maintains long dwell times
Coverage of high latitudes
4 satellites 6 hour look time to cover 24 hours continuous

PERIGEE - minimum distance to earth, maximum speed
APOGEE - maximum distance from earth, minimum speed

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28
Q

What is LEO?

A

Low earth orbit typically 2000km

1 orbit takes around 90 minutes

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29
Q

Explain geostationary orbit

A

Same angular velocity as the earth so remains looking at the same position of the earth. Circular equatorial orbit.
3 satellites to see 120 degrees each, 1 atlantic, 1 indian, 1 pacific, 17.5 degree beamwidth.

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30
Q

Explain geo-synchronous orbit

A

Elliptical inclined orbit where satellite appears at same position every 24 hours. Worldwide coverage except polar regions.

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31
Q

Explain Sub synchronous orbit

A

Lower than geo-synchronous, circular inclined orbit lasting upto 12 hours.

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32
Q

What are the pros and cons of the different orbit types?

A 
Geo-synchronous / stationary
Infinite dwell time over region
Ground stations dont require following antennae
Expensive to put into orbit
Impossible to repair

Sub-synchronous
Faster coverage of large areas
Require number of satellites for full coverage

LEO
Can be fixed
Decreased lag time
Need many satellites to give full earth coverage

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33
Q

What are the pros and cons of the different orbit types?

A 
Geo-synchronous / stationary
Infinite dwell time over region
Ground stations dont require following antennae
Expensive to put into orbit
Impossible to repair

Sub-synchronous
Faster coverage of large areas
Require number of satellites for full coverage

LEO
Can be fixed
Decreased lag time
Need many satellites to give full earth coverage

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34
Q

What the the 4 different beam types?

A

Global beam - 42%
Hemispheric beam - 20%
Zonal beam - 10%
Spot beam - 800km across

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35
Q

Purpose of a transponder? (Sub systems)

A

Receives multiple signals simultaneously and translates uplink signal frequency band to downlink frequency band.

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36
Q

Purpose of antennae (Sub systems)

A

Carry one or more antennae to produce a beam.

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37
Q

Purpose of telemetry and command (Sub systems)

A

Separate antennas :

Downlink: Engineering & equipment status info

Uplink: Commands to select equipment modes, change satellite orbit or maintain satellite orbit.

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38
Q

Purpose of attitude control (Sub systems)

A

Spin stabilisation - maintain antennae pointing at earth

3 axis stabilisation - Maintain body of satellite pointing to earth whilst solar panels at sun.

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39
Q

Purpose of orbit control (Sub systems)

A

Corrections to orbit N-S E-W using propulsion unit

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40
Q

Purpose of electrical power (Sub systems)

A

Solar panels with standby batteries 300w - 16kw

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41
Q

What is IADS? What are some examples?

A

Integrated air defence systems - multiple units operating cohesively to deny enemy air operations inside designated zone.

Missile sites
Data links
Fither aircraft
Naval vessels
Early warning radars
Tracking and Target acquisition radars
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42
Q

What is SEAD?

A

Suppression of enemy air defences

Neutralise or temporarily degrade enemy air defences
When DEAD isnt possible
Jamming or antiradiation missiles
May require multiple missions

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43
Q

What is DEAD?

A

Destruction of enemy air defences

Permanent suppression
Increased future safety
Frees up crew and resources
Preferred over SEAD

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44
Q

2 types of anti-radiation missile?

A

Hard kill (target continues to transmit until impact) & soft kill (EMCON switch off target, SEAD)

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45
Q

What is a TST?

A

Time sensitive targeting - targets that require immediate attention as they may or will pose a threat to friendly forces, are fleeting or highly lucrative.

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46
Q

What is joint targeting?

A

This is the whole process of determining the effects necessary to achieve commanders objectives with resources available. This is also the synchronisation of firing with other military authorities.

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47
Q

What is the TST process?

A

F F T T E A

Find 
Fix
Track
Target
Engagement
Assesment
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48
Q

What is dynamic targeting?

A

Prosecutes targets identified too late to be identified in deliberate targeting

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49
Q

What is deliberate targeting?

A

Prosecutes targets known to exist in operational area.

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50
Q

How can we engage TST targets?

A

Either method of deliberate or dynamic however due to fleeting targets, dynamic is most often used.

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51
Q

What is a multi-frequency radar?

A

Multi frequency radars use two or more illumination frequencies

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52
Q

What are the two types of multi frequency radars?

A 
Simultaneous transmission (Freq diversity)
Differing successive pulses (Freq agility)
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53
Q

Explain frequency diversity

A

Simultaneous transmission on two frequencies via 2 antennae and transmitters.

Short pulse - high discrimination short range
Long pulse - long range, detection of small aircraft

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54
Q

Explain frequency agility

A

The ability of a radar to switch frequencies in a controlled manner. The receiver is synchronised to the transmitter.

Anti clutter
Elims 2nd time round returns
EPM - hard to jam

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55
Q

What is a continous wave radar? Adv Disadv & apps

A

Single frequency transmitted continuously

Adv
Suitable for doppler measurement
High av power
Narrow bandwidth

Disadvantages
Seperate TX & RX
Cannot calculate range

Application:
Weapon guidance
Doppler nav

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56
Q

How can a CW radar measure range?

A

Frequency modulated continuous wave radar

Uses different frequencies and measures the time between transmission and echo

Interrupted continuous wave (coherent)
Provides range and velocity measurements
Predominantly pulse doppler radars

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57
Q

What is meant by a coherent signal?

A

signals are described as coherent if their phase relationships are constant

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58
Q

What is meant by interpulse?

A

What happens between pulses ie PRI

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59
Q

What is interpulse modulation?

A

The modulation of the interval between pulses (interpulse) to overcome the issues generated by utilising a single PRI.

These are:
False targets generated by 2nd time round returns
Blind ranges
Blind speeds

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60
Q

5 different types of interpulse modulation

A 
PRI steady/constant
PRI Stagger
PRI Jitter
PRI Dwell and switch
PRI Agility
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61
Q

Explain PRI steady / constant

A

Same PRI used all the time

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62
Q

Explain PRI Stagger

A

Small or large discrete PRI changes in recognisable pattern normally changing each pulse

Simple sequence: No. of staggers in sequence 7 or less
Complex: No. of staggers in sequence more than 7
Random sequence: Staggered PRIs in non predicatble non repetitive order
Pseudorandom: Repeats itself after a period of time

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63
Q

What is PRI Dwell and switch?

A

Small or large discrete PRI changes in a recognisable pattern changing after a set of pulses at each PRI

Separate dwells may be jittered
TA / TT / AI
Pulse doppler radars

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64
Q

What is PRI Jitter?

A

Apparently random small PRI changes

Discrete Jitter - Preset PRIs randomly between set limit
Random - No pattern between set limit

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65
Q

What is PRI agility?

A

Psuedorandom large PRI changes

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66
Q

What is pulse code modulation (multi-pulse)

A

Used for IFF, sonobouy and missile guidance.

Change of postion, order or other characterstics of pulse within frame.

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67
Q

What is firing order?

A

The order in which PRIs are transmitted - shortest PRI first

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68
Q

What is Element?

A

Describes an individual PRI

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69
Q

What are positions?

A

Describes total number of PRIs in cycle

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70
Q

What is cyclic length?

A

Time taken to complete a cycle in Ms

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71
Q

What is cyclic rate?

A

Inverse of cyclic length, no. of times sequence repeats in 1 second in Hz

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72
Q

What is mean PRI/PRF

A

Average of all the positions in the cycle

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73
Q

What is a frame?

A

Able to see full sequence of PRI before it repeats

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74
Q

What is Intra Pulse

A

Define what is happening to the PD of a signal

Is it modulated or unmodulated?

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75
Q

What are the 2 types of modulation?

A

Unintentional (UMOP)

Intentional

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76
Q

Explain UMOP

A

Unintentional Modulation on Pulse

Frequency, amplitude or phase variation from the intendended pulse

Specific Emitter Identification (SEI)

Fingerprint = old equipment or poor handling

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77
Q

Why modulate a pulse?

A

Modulation on Pulse = Pulse Compression

Range and Detection of a long pulse

with

Accuracy and resolution of narrow pulse

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78
Q

2 Types of Intentional Modulation

A

FMOP = Frequency Modulation on Pulse

PMOP = Phase Modulation on Pulse

79
Q

Explain FMOP

A

Also know as CHIRP

Frequency made to increase or decrease along the length of transmitted pulse

Frequency variation of the pulse is known as the sweep

Higher CHIRP = Better range resolution

Returns are passed through frequency delay lines

80
Q

Explain PMOP

A

Divides the pulse into equal segments called bits, uses binary to transmit data
1 = normal, 0 = reflected

Bi-phase = 180 degrees = Barker Coding
Quad-phase = 90 degrees = Frank Coding = Example of Polyphase

Codes can be changed pulse-by-pulse making them immune to certain types of repeater jammer (which FM waveform is vulnerable to)

More likely for long pulse duration

81
Q

What are the types of FMOP?

A

Linear Frequency Modulation On Pulse (LFMOP)

Non-Linear Frequency Modulation On Pulse (NLFMOP)

82
Q

Explain LFMOP

A

Used to ensure a good SNR at the receiver without sacrificing range resolution

Good range resolution and target discrimination

Suffers from some range ambiguites

It is a FM waveform so simpler and cheaper

83
Q

Explain NLFMOP

A

Sweeps the pulse frequency in a non-linear fashion

Aids sidelobe suppression

Poor range resoultion in comparison to LFMOP

But does not suffer as badly from range ambiguities

It is a FM waveform so simpler and cheaper

84
Q

Explain a Surface Acoustic Wave Device

A
85
Q

Explain Polyphase Coding

A

Basically PMOP but not limited to 0 or 180 increments

Still has to be harmonics

e.g. 0, 120, 240
0, 90, 180, 270 (Frank Coding)

86
Q

What are the limitations of Pulse Compression?

A

Receiver filters complicate the receiver
Transmission of a long pulse causes higher level of reflections (problems in sidelobes)
Long pulse increase the minimum range of the radar
FM and PMOP vulnerable to deception jammers

87
Q

What are the requirements of a Radar warning receiver? 10

A 
Sensitive
100% intercept probability
Wide range of frequencies
360 degree coverage in azimuth and relevant angles
Accurate and immediate direction finding
Measure parameters
Able to deal with all types of radar
Deinterleaves signals
ID emitter and prioritise
Display results clearly and provide alarms
88
Q

3 types of RWR

A

Crystal video receiver
Instantaneous frequency measurement receiver
Scanning superheterodyne receiver

89
Q

What are the features of a crystal video receiver CVR

A

Wide bandwidth
Simple/cheap/minimal programming

Unable to measure frequency
Poor sensitivity
Cannot detect continous wave

Overcome issues by adding more

90
Q

What are the features of a IFMR

A

Measures frequency
Measures quickly

Some do not provide PRF or PW
Only processes 1 signal at a time

91
Q

How to we overcome the limitations of CVR and IFMR?

A

By combining the two together

92
Q

What are the features of a Scanning superheterodyne

A

Very sensitive
accurate frequency measurement

Very complex compared to the others
Blind to frequencies it is not tuned to

93
Q

What is MDD and MDS?

A

Mission dependent data

Mission dependent software

94
Q

What is dwell?

A

The time a RWR will spend looking and a certain emitter dependent on its:

ARP
Beamwidth
PRF

95
Q

What is the ESM advantage (recommended to draw a picture)

A

RWR can detect emitter at a greater range before emitter can detect the return pulse from the RWR platform

96
Q

What is the definition of a countermeasure?

A

An action taken by a platform to negate the effect of a threat

97
Q

What are the two types of RF countermeasures

A

Electronic and mechanical

98
Q

What are the two types of electronic RF CM

A

Jamming

Deception

99
Q

What are the 3 types of jamming?

A

Spot
Sweep
Barrage

100
Q

What are the 3 types of deception?

A

Electronic repeater jamming —–

Range/velocity gate pull off
Angle deception
False target generation

101
Q

What are the two types of mechanical RF CM

A

Chaff

Decoys

102
Q

What are the two types of decoys?

A

Active

Passive

103
Q

Explain spot jamming

A

Spot jamming: covers 1 frequency with all of its power

Must know frequency
Must cover tx bandwidth

104
Q

Explain sweep jamming

A

Shifts frequency from 1 to another (spot jammer that moves)

Suffers from AGC and fade out

105
Q

Explain barrage jamming

A

Wide bandwidth covering multiple frequencies at once

Suffers from wasted energy and low power

106
Q

Explain radar burn through

A

When target radar power is more powerful than the jamming power. Usually occurs at closer range.

107
Q

EXplain false target generation

A

To produce on the victims radar display a set of returns which look like targets to confuse the operator. Does this by re transmitting the pulse earlier, later or into side lobes.

108
Q

What are the 3 types of deception?

A

False target generation
Angle lock breaking
Gate stealing

109
Q

What is range gate pull off?

A

Taking target lock on and re producing similar signal to your echo and relaying back to target with a time delay or time advance to make yourself appear closer or futher away

110
Q

What is velocity range gate pull off?

A

Walks off signal similar to range gate pull off but targets doppler radars which are measuring your speed

111
Q

What are the two types of active radar decoys?

A

Towed radar decoy

Expendable active decoy

112
Q

What are the 2 types of passive decoys

A

Chaff

Naval decoys

113
Q

What do decoys need to have to be effective?

A

Speed/velocity
Radar x section
Height

114
Q

What is chaff?

A

Elemental passive reflectors, absorbers or refractors of EM radiation.
Float and suspend in atmosphere
Replicate wavelength

115
Q

What does radar detection depend on?

A 
Low observability
Size
Shape
Material
Detection frequency
116
Q

Explain the engagement process

A

SATLI

Search
Acquire
Track
Launch
Intercept
117
Q

Explain search (Engagement process)

A

EW
CI
Height finding
Air traffic

118
Q

Explain acquire (Engagement process)

A

Acquire a target during search
Establish position

Target Acquisition Radar

119
Q

Explain track (Engagement process)

A

Accurate tgt position
Compute firing solution

Target Tracking Radar

120
Q

Explain launch (Engagement process)

A

Illuminate target
Establish seeker track
Maintain target

Target Illuminate Radar
Missile Guidance Radar
Fire Control Radar

121
Q

Explain intercept (Engagement process)

A

Maintain target illumination
Maintain seeker track
Fuse

122
Q

What are the 4 fire control radars?

A

Target acquisition
Target illumination
Target tracking
Missile guidance

123
Q

Explain target acquisition radar

A

Longest range
Lower frequency
Locates target and tracks if threat

124
Q

Explain Target tracking

A

TT is then pointed at target by TA
Looks further than weapons range
Higher frequency transmissions

125
Q

What are the features of a multi function array?

A

Electronically scanned phased array
Rapid and unpredictable scan in azimuth and elevation of sectors to around 90 degrees
G band
Utilises: freq agility, pulse compression, multiple PRF, pulse doppler.

126
Q

2 Types of missile guidance

A 
Command guidance
Homing guidance (semi active)
127
Q

What are the 3 types of homing guidance?

A

Passive
Active
Semi active

128
Q

Explain passive homing?

A

RF - Detects targets radar transmission using homing signal
IR - Detects target IR signature
UV - Detects target UV signature

Little or no warning
Doesnt now being tracked

No guarantee of hit

129
Q

Explain semi -active homing

A

Still homes passively
Ground platform transmits a powerful illumination signal at the target
Missile home in to reflected energy

130
Q

Explain active homing

A

Carries own radar and receiver
Homes onto own reflected energy of own transmissions
Downlink for initial guidance

131
Q

Explain active vs semi active seekers

A

Active = autonomous, expensive, complex, less room for explosives but passive until latter stages.

Semi active = requires launch platform to illuminate, vulnerable launch platform, can use AESA radar to engage multiple targets, cheaper, more explosive, target is aware.

132
Q

What can an AESA do?

A

Engage multiple targets at once?

133
Q

Explain command to line of site CLOS and COLOS

A

CLOS: Launch point follows target, missile is guided and commanded to stay LOS.

COLOS: Predicts point of interception

134
Q

What are the types of CLOS?

A

Manual
Semi automatic
Automatic

135
Q

Explain manual CLOS

A

Target and missile tracked manually (old technology)
Training intensive
Poor against fast moving targets

136
Q

Explain Semi auto CLOS

A

Target tracked manually

Missile tracked automatically

137
Q

Explain automatic CLOS

A

Target and missile tracked automatically

Can be EO or Radar

138
Q

What are the features of CLOS

A 
Cost
Poor trajectory efficiency
Launch pad vulnerability
Single fire channel
Alerts enemy ESM
139
Q

What are the 3 types of command links

A

Wire
Fibre optic
RF

140
Q

Explain track via missile

A

Uses semi active but calculations and commands are made on the ground not in the missile head

141
Q

Advantages of track via missile

A

More flexible
More accurate
EA resistant
Radar can track and illuminate multiple targets simultaneously

142
Q

What is SAGG seeker aided ground guidance

A

Similar to TVM
Ground station conducts early engagement
Missile tacks over during the latter stages
More jam resistant

143
Q

What are the requirements for a MWS?

A

SHLLATS

Spherical coverage
Long rage early warning
Speed
High probability of detection
Low FA rate
Aspect information
Threat lethality assessment
144
Q

Typical missile flight diagram

A

Eject - Boost - Sustain - Coast - Fuse

UV - eject boost sustain
IR - All apart from fuse
RF - Close range

145
Q

What does a MWS detect?

A 
An objects Radar cross section and relative velocity
Muzzle flash
Motor ignition
Motor plume 
Leading edge heating
Residual heat on motor
146
Q

MWS process

A

Detect - Track - Declare

147
Q

What are the issues with a MWS? 4

A

Launch may be outside of max detection range
Motor burn out too early
Emissions may be supressed
Clutter

148
Q

Factors affecting detection performance? 6

A 
Sensor location and FOV
Sensor sensitivity
Sensor resolution
Sensor angular discrimination
Reliability
Software
149
Q

What are the 4 types of MWS?

A

Radar
IR
UV
Laser

150
Q

Explain radar MWS

A

Incoming object should create doppler shift, affected by size, speed and approach angle

Advantages
All weather & accurate range and velocity

Disadvantages
Limited detection range
Overt

151
Q

Explain a UV MWS

A

Detects UV signature from rocket motors and muzzle flashes within solar blind range.

Advantages
Covert
Can detect ignition and in flight

Disadvantages
Can’t detect after MBO
Suffers atmospheric attenuation

152
Q

Explain IR MWS

A

Detects IR emissions from muzzle flush and rocket motors

Advantages
Long range
Detects all flight

Disadvantages
High FA rate
Serviceability and cost

153
Q

Explain Laser MWS

A

Must be able to dectect scattered laser energy or the laser itself. Looks for coherent pulsed fast rise time radiation with very narrow bandwidths.

Limited CM:
Absorption 
Jamming
Ablation
Reflection
154
Q

What parts of the spectrum to IR missiles operate?

A

1,2 & 4

155
Q

What are the IR sources on an AC

A 
Exhuast plume
Engine inlets
Leading edges
Nose
Engine Nozzles
156
Q

What is the purpose of an IRCM? (FLARES)

A

To create a larger IR signature than the AC.

157
Q

What is peak intensity?

A

Must radiate with sufficient intensity to be both credible and more attractive than the air platform

158
Q

What is fast rise time?

A

Must reach effective intensity prior to leaving missile FOV

159
Q

What is burn time?

A

Must maintain credible signature until target no longer in missile FOV

160
Q

What are the two types of IRCCMs and what are there IRCCCMs?

A

Dual Band Detector = Spectral Flares

Kinematic Flare Rejection = Aerodynamic Flares (Forward Firing)

161
Q

Explain Dual Band Detector

A

Looks at Band 1 and 4 to compare signatures

162
Q

Explain Kinematic Flare Rejection

A

Detects flares by the sudden change in the angle of the sensor head and ignores

163
Q

Explain Spectral Flares

A

Higher intensity then aircraft in all bands

164
Q

Explain Aerodynamic Flares (Forward Firing)

A

Fire forward to reduce angle change in the sensor head

165
Q

Explain BOL-IR Flares

A

AMD = Active Metal Decoy

Black Flares

Not visible and help against dual colour

166
Q

Explain MTV Flares

A

Effective against earlier missles but show at night and give off UV

167
Q

What are the three types of IR Jammers

A 
DIRCM = Directional
LIRCM = Large Aircraft
CLIRCM = Closed Loop Laser
168
Q

Explain a IRCM (Lamp System)

A

Emits modulated pulses similar to the ones used by missles for direction

Lamp System = Omnidirectional Emission = Wasted Energy = Less Effective range

169
Q

Explain DIRCM

A

MWS detects IR threat
Handed over to DIRCM
Focuses energy, better range for same power
Needs MDD to fire a pred-determined laser jamming sequence

170
Q

What are the advantages of a Laser IR Jammer?

A

Good jamming to signal ratio

Small aperture requirement = small device

171
Q

What are the challenges of a Laser IR Jammer?

A

Very narrow beam-width so requires stable and precise tracking controls

172
Q

Explain a CLIRCM

A

Closed Loop Laser IRCM

Reflected energy used to identify missle to determine best jamming signal

173
Q

What is a LPI RADAR and why do we use it?

A

A radar employing measures to avoid detection by passive radar detection equipment (RWR/ESM)

To overcome ESM advantage

174
Q

What are the three LPI Radar Levels?

A

LPID = Low Probability of Identification
Easily detectable but not easily identifiable

LPI = Low Probability of Interception
Can detect a target but not detected itself by ESM receiver at same range outside main beam

Quiet Radar
Can detect a target and not be detected by an ESM receiver located on the target

175
Q

What are the three types of LPI Radar Implementation?

A

Power Optimisation
Beam Control
Waveform Management

176
Q

Explain Power Optimisation (LPI Radar)

A

Ensures minimum necessary power radiated
Power level consistent with target RCS
Only transmit when operationally essential
Power reduced as range to target decreases
Use of atmospheric absorption

177
Q

Explain Beam Control (LPI Radar)

A

Narrow Mainlobe = less chance of being detected

Extremely Low Sidelobe Levels through Tapered Ilumination

178
Q

Explain Waveform Management (LPI Radar)

A

Signal energy spread in frequency reducing the signal strength and therefore the SNR in any receiver attempting to intercept

Tactics:
Frequency Hopping (Agility)
Chirping
Direct Sequency Spread Spectrum (DSSS)

179
Q

Explain Primary Radar

A

Sends out a pulse of RF, small proportion is reflected back to antenna

180
Q

Explain Secondary Radar

A

Ground station transmit a code signal at the target

Transponder responds to interrogation which replies with a coded signal

181
Q

Advantages of SSR?

A

Reply signal is much stronger when received at the ground station = greater range
Reduced transmitting power required by ground station for a given range = less cost
Signals in each direction are electronically coded = transmit additional information

182
Q

Disadvantages of SSR

A

Aurcraft has to carry an operating transponder –> primary used in foreseeable future
Ground antenna are highly directional but cannot be designed without sidelobes

183
Q

Applications of SSR?

A

Safety of flight through ATC ID/position
Safety of flight through TCAS
Communication of emergencies
IFF = stops blue on blue and ID hostiles

184
Q

Explain Fruiting

A

FRUIT = False Replies Unsynchronised with time
SSR interogates on 1030MHZ, aircraft transponder replies on 1090MHz
Ground station receives replies from aircrafts responding to other ground station
Can lead to indication of aircraft which does not exist

185
Q

Explain Garbling

A

Replies from two aircraft overlap if their range seperation is less than 20.3 microseconds in reply length (3.2 Nm)

186
Q

What are the Military IFF Modes and Civilian SSR Modes?

A 
Mil Mode 1
Mil Mode 2
Mil Mode 3 / Civ Mode A
Mil Mode 5
Civ Mode B
Civ Mode C
Civ Mode S
187
Q

Explain Mode 1

A

Cockpit selectable
2-digit misson code
designates aircraft type and mission

188
Q

Explain Mode 2

A

Assigned by command
4-digit octal unit code
unique identifier for a particular aircraft

189
Q

Explain Mode 3/Civilian A

A

Assigned by ATC
4-digit octal unit code
Who is controlling it

190
Q

Explain Mode C

A

Alitude information in increments of 100ft

Often combined with Mode 3/A

191
Q

What are the Emergency Mode 3/A Codes?

A

7500 Hijacking
7600 Lost Comms
7700 Emergency

192
Q

Explain Military Mode 5

A

Encrypted message of Mode 1,2,3/A,C

Enhanced secure data response

193
Q

Explain Civ Mode S

A

Automatic collision avoidance = Traffic Collision Avoidance System (TCAS)
Functions of Mode A/C
Reduces over interrogation of transponder

Advanced EW (5 decks)

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