Radartutorial .eu
Radar Basic Principles
The following figure shows the operating principle of a primary radar set. The radar antenna illuminates the target with a microwave signal, which is then reflected and picked up by a receiving device. The electrical signal picked up by the receiving antenna is called echo or return. The radar signal is generated by a powerful transmitter and received by a highly sensitive receiver.
Figure 1: Block diagram of a primary radar
All targets produce a diffuse reflection i.e. it is reflected in a wide number of directions. The reflected signal is also called scattering. Backscatter is the term given to reflections in the opposite direction to the incident rays.
Radar signals can be displayed on the traditional plan position indicator (PPI) or other more advanced radar display systems. A PPI has a rotating vector with the radar at the origin, which indicates the pointing direction of the antenna and hence the bearing of targets.
Transmitter
The radar transmitter produces the short duration high-power rf pulses of energy that are
into space by the antenna.
Duplexer
The duplexer alternately switches the antenna between the transmitter and receiver so that
only one antenna need be used. This switching is necessary because the high-power pulses of the
transmitter would destroy the receiver if energy were allowed to enter the receiver.
Receiver
The receivers amplify and demodulate the received RF-signals. The receiver
provides video signals on the output.
Radar Antenna
The Antenna transfers the transmitter energy to signals in space with
the required distribution and efficiency. This process is applied in an identical way on reception.
Indicator
The indicator should present to the observer a continuous, easily
understandable, graphic picture of the relative position of radar targets.
