Radar is an object detection system. To determine the range, speed,direction, of the object or altitude it uses radio waves. Pulses of radiowaves or microwaves transmits by radar dish or antenna which bounce off any object in their path. Dish antenna is located at the same site as the transmitter where the objects return a small parts of wave energy.
Use of radar: to detect aircraft, spacecraft, ships, guided missiles, motor vehicles, weather formation.
A long range radar antenna, known as ALTAIR.
The power Pr returning to the receiving antenna is given by the equation:
- Pt = transmitter power
- Gt = transmitting antenna gain
- Ar = effective aperture of the receiving antenna
- σ = radar cross section
- F = pattern propagation factor
- Rt = distance from the transmitter to the target
- Rr = distance from the target to the receiver
When Rt = Rr and Rt2 Rr2 can be replaced by R4 where R is the range gives the equation
This equation shows received power decreases as the fourth power of the range, it means from the distant targets reflected power is very small.
- Transmitter: Transmitter transmits short duration high power rf pulses to the space by antenna which are produces by radar transmitterDUPLEXER: antenna between the transmitter and receiver switches alternately by the duplexer so that only one antenna can be used. If energy were allowed to enter the receiver high power pulse of transmitter would destroy the receiver so the switching is necessary.RECEIVER: received RF signals is amplified and demodulated by the receiver. And it also provides the video signals at the output.RADAR ANTENNA: with the required distribution and efficiency antenna transfer the transmitter energy to the signal in space. same process is applied on the reception.INDICATOR: continuous, easily understandable and graphic picture of the relative position of the radar target is observed by he indicator.TYPES OF RADAR
- CW RADAR (continuous wave radar)
In CW radar continuous wave radio energy which is stable frequency is transmitted and then received from any reflecting object. Doppler, renders the radar to interference from large stationary object and slow moving cutter and radar uses Doppler.
Block diagram of CW radar.
2. FMCW RADAR(frequency modulated continuous wave radar):
The basic principle of operation of FMCW radar is imaging principle. Resolution for long range FMCW radar in range is less than 1meter and in azimuth is less than 1 degree. The operation of FMCW radar is independent of direction of travel of the target and speed of the travel of the target. Modern FMCW radar detects the people near zero speed and and walking in any dierection with respect to the radar.
3.MTI RADAR(moving target indication radar):
It is used to discriminate the target against clutter. The moving target will change the distance of given sequence of radar pulses from the radar system. So, the phase of the reflective radar pulses is different from successive pulses. And in the stationary target the phase is same.
Block diagram of MTI radar.
- It is proposed in 1842 which is named after Australian physicist Chiristian Doppler.For an observer moving relative to the source of the wave the difference between the observed frequency and emitted frequency is Doppler effect.Radar which uses Doppler effect is known as Doppler radar to produce velocity data about object at a distance. And it is done by beaming a microwave signal towards a desired target and listening its reflection. And then analyze by the object motion how the frequency of the returned signal has been altered.
QUESTION & ANSWER-
- What are the use of Doppler radar??
ANS-Use of Doppler radar-
- Sounding satellites
- Police speed gun
- Radiology 2.What is Doppler effect??
ANS-For an observer moving relative to the source of the wave the difference between observed frequency and emitted frequency of the wave is known as Doppler effect. And it is named after Austrian physicist Christian Doppler in 1842.
3.What is a radar??
ANS-Radar is an object detection system. to determine the range direction speed of the object or altitude. It uses radio waves .
4. What are the use of radar??
ANS-Radar is used to detect
- Guided missiles
- Weather formation etc. 5. Give the names of type of radar???
ANS-Types of radar
- CW RADAR(continuous wave radar )
- FMCW RADAR(frequency modulated continuous wave radar )
- MTI RADAR(moving target indication ra