TYPES OF RADARS
A variety of radars have been developed and they are classified based on
1. The signal transmitted.
2. The target of interest and
3. The frequency of operation.
Some of the commonly used radars are discussed as follows.
CONTIUOUS WAVE (CW) RADAR
The radar transmitter transmits a continuous signal rather than a pulse one. The echo signal can be easily distinguished from the transmitted signal as there will be a shift in the frequency of the echo signal due to the DOPPLER EFFECT. Also, the echo signal’s strength is many times lower than the transmitted signal strength.
Using a CW radar, the relative velocity of a target can be determined. The drawback of a CW radar is that the range of the target cannot be determined.
MOVING TARGET INDICATION (MTI) RADAR
The MTI radar transmits a train of electromagnetic pulses. This radar system is capable of distinguishing a moving target from the non-moving objects. The non-moving objects in atmosphere that intercept the transmitted signal and scatter it are called CLUTTER. Since there will not be any DOPPLER frequency shift from fixed targets, as there is no relative motion, they are easily identified from the moving target. The echo from the moving target has the varying frequencies due to DOPPLER EFFECT.
TRACKING RADAR
A tracking radar system locks on to a particular target, measures its coordinates and provides data from which the future course of the target can be predicted.
The tracking radar is similar to other radars except that the antenna beam of a tracking radar is made to look at the target always. This is achieved by a servomechanism activated by error signals. The error signals is obtained using several techniques, viz. sequential lobing, conical scan and simultaneous lobing.
APPLICATIONS OF RADAR
Radar systems find their applications on the ground, in the air, on the sea and in space. The ground based radars have been used in the detection, location and tracking of aircraft or space targets. The shipboard radars are used to navigate the ships and to locate buoys, shorelines and other ships. They are also used to observe aircraft. The airborne radars are used to detect land vehicles, ships and aircraft. However, the principal application of airborne radar is for mapping of land storm avoidance and navigation. In space, radar is used for remote sensing purposes.