Week 1 Flashcards
What is the formula that converts numbers to dB’s?
(Log X Number) X 10 = dB
What is the number that converts dB’s to numbers?
dB/10 = Ans. 10 to the power of Ans = Number
Define bandwidth
Bandwidth is the difference between the upper and lower frequencies of the signal. (In Hz)
List the four external factors effecting SNR.
Distance from source
Jamming
No LOS/Multi-path interference
Atmospheric conditions.
In a Raster Scan, what is a Bar and what is a Frame?
Bar: line of search
Frame: Complete cycle of bars (search area).
What are the two types of sector scan?
Bi-directional
Uni-directional
Tracking scans include what?
Lobe switching
Monopause
Conical
What are the two types of phased array?
Passive
Active
What would you expect to see in an antenna design?
Feed
Reflector
Transmitting Medium:
Waveguide & Coaxle
Define Beamwidth
The 1/2 power points on the main lobe (-3dB)
Benefits small beamwidth
Angular location
Angular discrimination
List the types of lobes
Main/major lobe
Side/minor lobe
Back lobe
List the types of array/beam steering:
Mechanical
Electrical - Changing Freq & Phase.
What does DOA stand for?
Direction of Arrival
Describe the term Ellipse.
Very rarely is the DF pinpoint so the position is described as an ellipse.
What is an Ellipse?
The length of its major axis
The length of its minor axis
It’s orientation
The position of the centre
List the two types of DOA measurements?
Amplitude Comparison
Phase Comparison
Differences between phase and amplitude comparison.
Phase can be accurate to 1.5 degrees.
Amplitude is not very accurate - to about 10 degrees.
What do most RWRs use?
Power measurement.
What is the RWR detection sequence?
Identifies Measures received PWR Compares to the known transmitter PWR Range calculated Warning given.
What does RWR rely on?
ELINT gathering
Ability of MA (EW) operators
What four things should ES receivers do?
Intercept
Measure
Identify
Display
Define Unintentional Pulse Modulation
Unintentional Pulse Modulation is caused by system noise & different operation. It helps with Specific Emitter Identification (SEI)
List in order an ES receiver system.
Antennae - Amplifier - Receiver -Processor - Outputs.
Between Receiver & Outputs - DOA Resolver.
3 types of ES Receiver
Threat Warning
Tactical systems
Strategic systems
List the 3 types of radar display.
PPI
B-scope
A-scope
List the 6 types of target information
Range Bearing Height Course Speed Shape/size/outline
What are the factors effecting radar?
Frequency PRF PW Power Beamwidth ARP Antenna Weight
Define Isotropic Source
Waves go in all directions equally
Label Transmit and Receive Diagram
Synchroniser - Modulator - Transmitter - Switch - Antenna - Receiver - Display
List the 3 types of Pulse Modulation
Amplitude
Frequency
Phase
List the 3 Transmission Devices
Magnetron
Travelling Wave Tube
Field Effect Transistor
3 uses of Radar Systems
Military uses
Weather
Nav Aids
What are the 2 main things in a Radar System
Transmitter
Receiver
3 types of fading
Skip Fade
Multi path Fade
Polarisation Fade
What two layers of the Earths Atmosphere have most major effect on EM waves?
Ionosphere
Troposphere
What does MUF stand for?
Max usable frequency
What is a Temperature Inversion caused by?
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.
List 3 prime areas for temperature inversions to occur
North Africa
Middle Easy
Mediterranean
Where to atmospheric anomalies take place?
Troposphere
List the 4 wave types
Ground waves
Surface waves
Space waves
Sky waves
Define Reflection
Angle of incidence = angle of reflection, as measured from the normal to the surface.
The incident ray & reflected ray lie in the same plane.
Reducing what is important for stealth aircrafts?
Glint & Scintillation
What are the 2 types of attenuation?
Absorption
Scattering
Define atmospheric attenuation
The weakening of signal at is propagates through the atmosphere
Define power density
The amount of energy per unit area
What are the 3 types of Polarisation?
Random
Linear
Circular & Elliptical
What form a square wave?
Odd harmonics
How far does an EM wave travel in 1 microsecond?
300m
984ft
0.162NM
Define Analogue System
Some sources consist of a variable quantity which changes continuously through time.
Define Digital Signal
Consists of a series of discrete permitted values with time.
To convert GHz to MHz what do you do?
Take away 6 zeroes.
What are the 3 measurements for the speed of light
3 X 10 to the 8
162000 Nm/s
186000 M/s
What does RADAR stand for?
Radio Detection and Ranging
What two fields are there in terms of EM waves?
H-Field
E-Field
What is SNR
Signal to Noise Ratio.
The ratio that describes a radars ability to see targets in presence of noise.
List 3 types of internal noise
Equipment noise
Antenna noise
Transmission noise
What is an advantage of an active phased array over a passive phased array?
Active is multifunction, if damaged you can turn off damaged cells and the rest will carry on working.
What function would you expect a radar with the following parameters to have?
Freq 1.3GHz
PRF 300
PW 9
ARP 8
LREW
