Radar Design Factors Flashcards
What is the requirement of a radar design?
To identify the range and bearing, or azimuth, of targets within its range to an acceptable resolution.
What is the resolution of a Radar?
The accuracy to which the radar can identify the range and bearing, or azimuth of each target.
Ie, The higher the resolution, the clearer the traffic picture which can be delivered
What are the factors that determine a radars coverage?
Aerial size, shape and height above ground
Atmospheric Conditions
Transmitter Power
Receiver Efficiency
Size of the Target (Primary)
Pulse Recurrence Frequency (Primary)
Pulse Length (Primary)
What type of beam does an Aerial have?
A narrow beam in azimuth, with a wide beam in elevation. A narrow beam requires large dimensions.
What is the usual aerial beam width?
Usual beam width is 2-3 degrees, which at 60nm gives a coverage of 2-3nm.
For a given aerial height, will a shorter wavelength give you more gaps in high coverage?
Yes. For a given aerial height, the shorter the wavelength the more gaps in high coverage but the better will be the low coverage.
Conversely, for a given aerial height, the longer the wavelength the fewer gaps in high coverage but the low coverage will be poorer.
What is the optimum service volume of a single radar installation?
A cylindrical area extending up to about 60,000ft with a radius of about 200 NM, however much of this will be wasted energy.
ATC radar’s therefore tend to use the ‘cosecant squared’ radiation pattern. Massaging out the pattern to a more useful one.
What is a Vertical Coverage Diagram?
A Vertical Coverage Diagram will display the theoretical coverage of the radar display being described.
What is a Unit Coverage Diagram?
A Unit Coverage Diagram (UCD) shows the actual coverage of the radar system after it has been installed at a specific location.
It takes into account the local terrain, hills, valleys etc. and thus it is unique to each particular installation.
What are the operational procedures for Radar based on?
UCD for each unit
Are shorter or longer wavelengths more affected by the atmosphere?
Generally, the shorter the wavelength the greater the atmospheric effect.
What are some atmospheric effects?
Absorption or Attenuation, reducing signal strength
Reflection or Scattering creating clutter
Bending of the Radar, caused by atmospheric ducts causing super-refraction or anoprop, displaying radar echoes from excess ranges.
Why is Transmitter Power important?
Radar energy will be attenuated with distance.
Therefore, the transmitted power must be sufficient enough to allow for attenuation and still detect an aircraft at maximum range.
Why is PRF important for Primary Radar?
Pulse-Recurrence Frequency determines the maximum range of the primary radar. Higher PRF, lower range. This is because a high PRF doesn’t give a far object enough time to return an echo. PRF also determines the strength of the return number of hits on a target and therefore the strength of the return on a Primary Radar.
Why is Pulse Length important for Primary Radar?
The pulse length affects the minimum range of a primary radar.
This is because a long pulse length does not allow for a nearby reflection to be captured.
