Graphics Programs Reference
In-Depth Information
Introduction to Radar
Basics
Chapter 1
1.1. Radar Classifications
The word radar is an abbreviation for RAdio Detection And Ranging. In
general, radar systems use modulated waveforms and directive antennas to
transmit electromagnetic energy into a specific volume in space to search for
targets. Objects (targets) within a search volume will reflect portions of this
energy (radar returns or echoes) back to the radar. These echoes are then pro-
cessed by the radar receiver to extract target information such as range, veloc-
ity, angular position, and other target identifying characteristics.
Radars can be classified as ground based, airborne, spaceborne, or ship
based radar systems. They can also be classified into numerous categories
based on the specific radar characteristics, such as the frequency band, antenna
type, and waveforms utilized. Another classification is concerned with the
mission and/or the functionality of the radar. This includes: weather, acquisi-
tion and search, tracking, track-while-scan, fire control, early warning, over
the horizon, terrain following, and terrain avoidance radars. Phased array
radars utilize phased array antennas, and are often called multifunction (multi-
mode) radars. A phased array is a composite antenna formed from two or more
basic radiators. Array antennas synthesize narrow directive beams that may be
steered mechanically or electronically. Electronic steering is achieved by con-
trolling the phase of the electric current feeding the array elements, and thus
the name phased array is adopted.
Radars are most often classified by the types of waveforms they use, or by
their operating frequency. Considering the waveforms first, radars can be Con-
