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EW ADV > Week 1 > Flashcards

Week 1 Flashcards

1
Q

What is the formula that converts numbers to dB’s?

A

(Log X Number) X 10 = dB

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2
Q

What is the number that converts dB’s to numbers?

A

dB/10 = Ans. 10 to the power of Ans = Number

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3
Q

Define bandwidth

A

Bandwidth is the difference between the upper and lower frequencies of the signal. (In Hz)

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4
Q

List the four external factors effecting SNR.

A

Distance from source
Jamming
No LOS/Multi-path interference
Atmospheric conditions.

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5
Q

In a Raster Scan, what is a Bar and what is a Frame?

A

Bar: line of search
Frame: Complete cycle of bars (search area).

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6
Q

What are the two types of sector scan?

A

Bi-directional

Uni-directional

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7
Q

Tracking scans include what?

A

Lobe switching
Monopause
Conical

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8
Q

What are the two types of phased array?

A

Passive

Active

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9
Q

What would you expect to see in an antenna design?

A

Feed
Reflector
Transmitting Medium:
Waveguide & Coaxle

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10
Q

Define Beamwidth

A

The 1/2 power points on the main lobe (-3dB)

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11
Q

Benefits small beamwidth

A

Angular location

Angular discrimination

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12
Q

List the types of lobes

A

Main/major lobe
Side/minor lobe
Back lobe

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13
Q

List the types of array/beam steering:

A

Mechanical

Electrical - Changing Freq & Phase.

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14
Q

What does DOA stand for?

A

Direction of Arrival

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15
Q

Describe the term Ellipse.

A

Very rarely is the DF pinpoint so the position is described as an ellipse.

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16
Q

What is an Ellipse?

A

The length of its major axis
The length of its minor axis
It’s orientation
The position of the centre

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17
Q

List the two types of DOA measurements?

A

Amplitude Comparison

Phase Comparison

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18
Q

Differences between phase and amplitude comparison.

A

Phase can be accurate to 1.5 degrees.

Amplitude is not very accurate - to about 10 degrees.

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19
Q

What do most RWRs use?

A

Power measurement.

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20
Q

What is the RWR detection sequence?

A 
Identifies 
Measures received PWR
Compares to the known transmitter PWR 
Range calculated
Warning given.
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21
Q

What does RWR rely on?

A

ELINT gathering

Ability of MA (EW) operators

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22
Q

What four things should ES receivers do?

A

Intercept
Measure
Identify
Display

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23
Q

Define Unintentional Pulse Modulation

A

Unintentional Pulse Modulation is caused by system noise & different operation. It helps with Specific Emitter Identification (SEI)

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24
Q

List in order an ES receiver system.

A

Antennae - Amplifier - Receiver -Processor - Outputs.

Between Receiver & Outputs - DOA Resolver.

25
Q

3 types of ES Receiver

A

Threat Warning
Tactical systems
Strategic systems

26
Q

List the 3 types of radar display.

A

PPI
B-scope
A-scope

27
Q

List the 6 types of target information

A 
Range 
Bearing
Height
Course
Speed
Shape/size/outline
28
Q

What are the factors effecting radar?

A 
Frequency 
PRF
PW
Power
Beamwidth
ARP
Antenna
Weight
29
Q

Define Isotropic Source

A

Waves go in all directions equally

30
Q

Label Transmit and Receive Diagram

A

Synchroniser - Modulator - Transmitter - Switch - Antenna - Receiver - Display

31
Q

List the 3 types of Pulse Modulation

A

Amplitude
Frequency
Phase

32
Q

List the 3 Transmission Devices

A

Magnetron
Travelling Wave Tube
Field Effect Transistor

33
Q

3 uses of Radar Systems

A

Military uses
Weather
Nav Aids

34
Q

What are the 2 main things in a Radar System

A

Transmitter

Receiver

35
Q

3 types of fading

A

Skip Fade
Multi path Fade
Polarisation Fade

36
Q

What two layers of the Earths Atmosphere have most major effect on EM waves?

A

Ionosphere

Troposphere

37
Q

What does MUF stand for?

A

Max usable frequency

38
Q

What is a Temperature Inversion caused by?

A

Warm air moving over cold air.
The sea keeping lower layers cooler than the air above it
The earth at night cooling and conducting heat away from the air above it.

39
Q

List 3 prime areas for temperature inversions to occur

A

North Africa
Middle Easy
Mediterranean

40
Q

Where to atmospheric anomalies take place?

A

Troposphere

41
Q

List the 4 wave types

A

Ground waves
Surface waves
Space waves
Sky waves

42
Q

Define Reflection

A

Angle of incidence = angle of reflection, as measured from the normal to the surface.
The incident ray & reflected ray lie in the same plane.

43
Q

Reducing what is important for stealth aircrafts?

A

Glint & Scintillation

44
Q

What are the 2 types of attenuation?

A

Absorption

Scattering

45
Q

Define atmospheric attenuation

A

The weakening of signal at is propagates through the atmosphere

46
Q

Define power density

A

The amount of energy per unit area

47
Q

What are the 3 types of Polarisation?

A

Random
Linear
Circular & Elliptical

48
Q

What form a square wave?

A

Odd harmonics

49
Q

How far does an EM wave travel in 1 microsecond?

A

300m
984ft
0.162NM

50
Q

Define Analogue System

A

Some sources consist of a variable quantity which changes continuously through time.

51
Q

Define Digital Signal

A

Consists of a series of discrete permitted values with time.

52
Q

To convert GHz to MHz what do you do?

A

Take away 6 zeroes.

53
Q

What are the 3 measurements for the speed of light

A

3 X 10 to the 8
162000 Nm/s
186000 M/s

54
Q

What does RADAR stand for?

A

Radio Detection and Ranging

55
Q

What two fields are there in terms of EM waves?

A

H-Field

E-Field

56
Q

What is SNR

A

Signal to Noise Ratio.

The ratio that describes a radars ability to see targets in presence of noise.

57
Q

List 3 types of internal noise

A

Equipment noise
Antenna noise
Transmission noise

58
Q

What is an advantage of an active phased array over a passive phased array?

A

Active is multifunction, if damaged you can turn off damaged cells and the rest will carry on working.

59
Q

What function would you expect a radar with the following parameters to have?

Freq 1.3GHz
PRF 300
PW 9
ARP 8

A

LREW

EW ADV (1 decks)

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