Radar Transmission And Processing Flashcards
What are the two many ways of removing unwanted returns on Radar?
Moving Target Indicator (MTI)
Circular Polarisation
What type of clutter does circular polarisation remove?
Weather clutter
Is circular polarisation switched on continuously?
No because it can mask some returns.
Is it possible to stop circular polarisation from masking returns?
Yes. The receiver can be gated to ignore such returns and allow a/c to be seen.
What is PSR fitted with in order to help move Ground Clutter?
Moving Target Indicator (MTI)
What does MTI remove from the radar screen?
Ground clutter
How does MTI work?
It displays echoes from moving targets(aircraft) and rejects echoes from fixed Targets (Permanent Echoes (PE))
What is the problem with MTI?
It’s dependent on radial moment of the aircraft between Successive pulses.
If the a/c is flying tangentially/perpendicular to the radar beam the aircraft movement will not have a radial component.
If the radar fails to display the radial component of an aircraft on the screen what is called?
Tangential Fading
What will happen if the aircraft changes its radial distance by half a
Wave length?
There will be no
Doppler effect and cancellation of the blip will occur. Known as Blind Velocity fading
How does Blind Velocity Fading Occur?
When aircraft fly directly towards or away from the radar scanner
Blind Velocity fading will also occur when the distance is a multiple of half a wavelength true or False?
True.
The speed at which blind Velocity fading occurs is known as
Blind velocities
List the 4 ways of data being transmitted.
1) Microwave link
2) Satellite
3) Line of site
4) Telephone/fibre optic cable
The method of Transmitting data will depend on 2 factors.
1) The nature of the signals (analogue or digital)
2) The distance to be covered
Describe Coaxial cables
1) Limited to Shirt Distance
2) Expensive
3) signal deteriorates rapidly
Describe Radio Link
1) Operates in SHF + UHF frequency band
2) for long distance radar information must be monitored and repeated at various stages along the route.
3) To avoid Interference the frequency is changed at each radio link repeater
Fibre Optics
Used for relatively short distances (e.g. between radar site and control tower)
Can telephones be used for data transmission?
If they are sufficiently high grade and if the information being sent in a processed form (digital Forma plot extractor)
Use of plot extractors at radar sites
High grade transmission line la and suitable error checking process enables a high standard of reliability to be maintained.
How can caps in radar coverage be reduced/eliminated?
If information from a variety of sources can be presented on display.
To achieve reducing gaps in radar display the airspace is divided into a grid of squares. What are the size of the squares? What do they form?
16nm x 16nm
Columns of air from the ground upwards called Radar sort boxes
How many radar systems can be in a Radar Sort Box?
Up to 4
Depending on the number of systems which can provide a service.
The radar giving the best cover in the Radar Sort Boxes is nominated the?
Preferred
The radar providing the next best cover in the Radar Sort Boxes is the
Supplementary
The remainder radars in the Radar Sort Box which is neither the preferred or Supplementary make up the?
Reserve
If the preferred radar fails the Supplementary radar can be upgraded either manually or automatically to “preferred” and a reserve upgrades to “Supplementary”.
True or False?
True.
List the 8 things the Plot Extractor does
1) Decides validity of Targets
2) Calculates correct azimuth and range data
3) Decides is target is primary, secondary or a combination
4) Correlates code data in both identity and height modes
5) Checks for emergency/radio fails and SPI indicators
6) Produces one complete target report per a/c per aerial revolution and outputs this in digital form
7) Produces synchronised message
8) Produces North Mark messages
Data from the flight plan database can be processed with radar signal date, enabling useful information to be presented on the radar screen. This includes:
1) conversion of SQK to a/c callsign
2) A/C destination included in radar response label
By examining the past movement of radar returns the signal processor can calculate and display ground speed.
True or False?
True.
The process of flight can be displayed as trail dots and predictions of the future position of the aircraft can also be displayed by the signal processor.
True or False?
True.
List all 5 moveable data
1) DF Bearing Lines
2) Electronic Range n Bearing Marker (ERBM)
3) Electronic cursor
4) Symbols
5) Alpha Numerics
List all 7 items in display of information (video map)
1) significant points (nav aids)
2) Final approach Track with ranges
3) Airspace restrictions
4) CAS Boundaries
5) Coastlines and Rivers
6) FIR n National Boundaries
7) Latitude and longitude
What is Track Fusion?
It is data from several antennae combined in all parts of the screen. processor determines an average position for each aircraft based on returns from Antenna.
Reduces inaccuracies in displayed position.
With Track Fusion it can produce an uninterrupted display of aircraft even if one radar fails. True or False.
True.
What does Surveillance Radar Networking do?
Shares radar data with all units in the network.
Provides enhance coverage and extra redundancy and allows multi Radar processing and track fusion.
