Describe common RADAR systems.
- Search Radar systems
- A search RADAR must scan a volume of space at regular
intervals to locate targets. - The RADAR beam is scanned repeatedly over that entire
volume. - Search RADARs maybe also referred to as Surveillance or
Acquisition RADARs. - Search RADARs scan using a 2 or 3 dimensional (2D-3D)
process. - 2 Dimensional Search RADARs are able to obtain Target
Azimuth and Range. - 3 Dimensional Search RADARs are able to obtain Target
Azimuth, Range and Elevation.
Describe common RADAR systems.
- Tracking Radar systems
- Target tracking requires greater accuracy and higher data rates.
- Tracking RADARs use narrow beams to follow a target in track.
- Tracking RADARs provide continuous update of target range, azimuth and
elevation. - Tracking RADAR normally works in conjunction with search RADAR.
Describe Search radar - 2D Scan
- The RADAR beam is narrow in azimuth but broad
in elevation to ensure coverage of the desired
volume of space. - Targets are at the same azimuth but different
ranges are resolved in range and azimuth. - Targets at different azimuths and the same range
are resolved in range and azimuth. - Targets at the same azimuth and range, with large
separation in elevation are not resolved.
A single target is detected and displayed.
Describe Search radar - 3D Scan
- 3D RADARs use a single antenna and
vertically stacked beams to resolve range,
azimuth and elevation. The RADAR beams
must have both a narrow horizontal and
vertical beam width.
Describe common RADAR antenna effect radiation patterns.
how does the antenna effect the transmitted wave
*The RADAR function determines the antenna radiation pattern
required.
*The physical shape of the antenna will determine the radiation
pattern.
*The physical size of the antenna will be determined by the Radio Frequency.
Describe pencil beam
- Both narrow vertical and horizontal beamwidths.
- Resolution in both azimuth and elevation.
- Primarily for tracking RADAR applications.
Describe fan beam
- Search Application.
- directional antenna producing a main beam having a narrow beamwidth in one dimension and a wider beamwidth in the other dimension.
- Narrow horizontal beamwidth enables azimuth resolution.
- Broad vertical beamwidth enables volumetric coverage of wide angular regions in the elevation plane.
Describe shaped or spoiled beam
Beam shaped or spoiled to produce more energy
above or below the antenna centerline.
(Maritime radar)
Describe arrays
- An array is comprised of a number of individual radiators.
- These radiators may be a series of slots in wave-guides, or individual dipoles.
- The individual radiators are known as elements.
- In more advanced arrays, each element may be individually controlled in Phase and Amplitude.
State the characteristics of the following RADAR antennas
- Slotted Waveguide
- The slotted waveguide is comprised of a number of slots cut into a single waveguide.
- If the slots are arranged in a line the antenna is referred to as a linear array.
- Energy is fed into one end of the waveguide and propagates from
the slots cut in the waveguide face. - The slots are spaced at approximately 1/2 wavelength such that the slots fall within each others induction field.
- The fields interact to produce a radiation pattern that is the sum of
the individual slots (elements).
Usually on maritime vessels
State the characteristics of the following RADAR antennas
- Cassegrain
- Contains 2 reflectors.
- Feed at the rear of the primary reflector
- A secondary reflector focuses radiation on the primary
reflector for beam forming.
State the characteristics of the following RADAR antennas
- Parabolic
- The true parabolic antenna shape focuses the radiation from the feed into a pencil beam.
- Different reflector shapes can be used to form differing beams patterns.
State the characteristics of the following RADAR antennas
- Phased Arrays
Single transmitter/receiver
Each element can be phase shifted independently (can track multiple targets)
Multiple beam shapes
Electronic Scan
State the characteristics of the following RADAR antennas
- Planar Arrays
- Single transmitter/receiver
- Multiple antenna radiator elements
- Each element is in phase
- Beam forming achieved by element selection
- Mechanically scanned
State the characteristics of the following RADAR antennas
- Active Arrays
- Each element is a
separate Tx/Rx - Electronic Scan
- Multiple Beam shapes
- Graceful degradation
- Higher efficiency
State the characteristics of the following RADAR antennas
- Conformal Arrays
Conformal arrays are antenna arrays shaped to fit the object they are being attached to.
