Radar Presentation

RADAR

:Submitted By: Makwana Hardik N

- RAdio Detection And Ranging

Classification of RADAR

Submitted by: Makwana Hardik N

First Classification:


Primary Classification:

A primary radar transmits high frequency signals which are reflected at targets.

The arisen echoes are received and evaluated. This means, unlike secondary

radars a primary radar receive it's own emitted signals as an echo again. In the

other way the primary radar illuminates its surrounding, like a searchlight, and

picks up part of the energy scattered by the objects it illuminates. Monostatic

radars, the majority of all radars, use the same antenna for transmission, or

illumination, and reception.

Such a radar that shown in this figure .


If the transmitter sends short pulses, the scattered energy from the objects

that from the environment are copies of the transmitted pulses with a time delay proportional to the

distance traveled, as with a sound echo. The frequency of the echoes, as with sound, depends on the rate

of change of range or radial velocity. Thus the echoes from the objects in the shown figure may be classed

from fastest, probably the aircraft echoes, through ground vehicle and rain clutter to the waving of the

trees. There are two type of primary radar, pulsed radar and continuous wave radar.

Pulsed Radar:


Radar transmit a high frequency impulsive signal of high power, after

each pulse is transmitted, the transmitter Pulsed is inactive for a fixed period of

time during which the receiver waits for echoes of the transmitted pulse. The range

of a target can be determined by measuring the time it takes for a pulse to travel

from the antenna to the target and back to the antenna. The pulses that was

transmitted is propagate at the speed of light .


Timer:The timer generates a series of narrow timing ( trigger ) pulses which

are used to start the transmission and indicator's time base at same time .

Modulator:On each trigger pulse the modulators generates a pulse waveform of

high enough amplitude to switch on the high power microwave oscillator .

Duplexer:The generated RF pulses is fed to the antenna through the duplexer

which consists of two microwave switch

.


Antenna:Is usually used for both transmitting and receiving .

Low Noise RF Amplifier:

The received energy is fed to a low noise RF amplifier used in order to improve the

receivers sensitivity by decreasing the over all noise .

Mixer:The mixer provide difference between the carrier frequency and the local oscillator

frequency. This is called intermediate frequency IF. The IF component of the mixer current is

selected by means of a microwave resonance circuit at the mixer's output. Therefore the

mixer translate the received signal on the frequency axis from the RF portion to the IF one

where it is much easier to be amplified .


ATR:It is called (anti-transmit-receive) switch and is functionless during transmission but

is closes the path to the transmitter during reception. Hence the

whole received energy will be delivered to receiver and nothing of it will be dissipated

in the transmitter circuits. Furthermore no noise leak from transmitter to receiver during the

reception time.

TR:It is called ( transmit receive ) switch and its function is opposite to that of the ATR

switch. It means that it disconnects the

receiver during transmission in order to protect its input stages from being damaged

by the high transmitted power and reconnects the receiver after a short time called the

recovery time trecov which is slightly greater than the pulse

duration. It determine the minimum distance Rmin from the radar at which target can be

detected as :


Pre Selector:It is used before the mixer in order to suppress any received signals at the image

frequency .

IF Amplifier Demodulator:The output IF pulses from the mixer are fed to the IF amplifier. In non-coherent pulse

radars the IF amplifier has a rectangular band pass characteristic with linear phase shift .

Envelope Detector:The IF amplifier is followed by an envelope detector that demodulates or removes

the pulse from its IF carrier . Note that envelope detection is a nonlinear operation whereas

all the preceding operations, on the received signal, are linear .


Video Amplifier:The video amplifier following the detector is used to increase the pulse to an

amplitude sufficient to operate the output display .

Indicator:The echo pulse from the video amplifier is presented on the indicator, most oftenly a

PPI . The start of the time base at the center of the screen synchronized with the start of

transmission by means of a servo system. Thus the angle of the time base at any time

indicates directly angle of the antenna at the same instant and the distance of the bright

soot from the center, indicates the range .

First Classification:


Secondary Classification:

Military Radar:The military radar was divided into three type, Air Defence , Battlefield , and Air

Traffic Control . Let us start with the first type, the Air DefenceRadar .

Air DefenceRadar:

Air defense radars can detect air targets and determine their position, course,

and speed in a relatively large area. The maximum range of air defense radar can exceed 300 miles,

and the bearing coverage is a complete 360 degree circle. Air defense radars are usually divided

into two categories, based on the amount of position information supplied. Radar sets that provide

only range and bearing information are referred to as two dimensional, or 2D radars. Radar sets

that supply range, bearing, and height are called three dimensional, or 3D radars .

Air defense radars are used as early warning devices because they can detect

approaching enemy aircraft or missiles at great distances. In case of an attack, early detection of

the enemy is vital for a successful defense against attack. Another function of the air defense radar

is guiding combat air patrol (CAP) aircraft to a position suitable to intercept an enemy aircraft. In

the case of aircraft control, the guidance information is obtained by the radar operator and

passed to the aircraft by either voice radio or a computer link to the aircraft .


Air DefenceRadar:1- Surveillance :-

Air search radar systems initially detect and determine the

position, course, and speed of air targets in a relatively large area.

The maximum range of air search radar can exceed 300 miles,

and the bearing coverage is a complete 360 degree circle. Air

search radar systems are usually divided into two categories,

based on the amount of position information supplied. Radar sets

that provide only range and bearing information are referred to

as two dimensional , or 2D radars. Radar sets that supply range,

bearing, and height are called three dimensional, or 3D radars .

1- Surveillance :-


Air search radar systems initially

detect and determine the position, course,

and speed of air targets in a relatively large

area. The maximum range of air search

radar can exceed 300 miles, and the

bearing coverage is a complete 360 degree

circle. Air search radar systems are usually

divided into two categories, based on the

amount of position information supplied.

Radar sets that provide only range and

bearing information are referred to as two

dimensional , or 2D radars. Radar sets that

supply range, bearing, and height are

called three dimensional, or 3D radars .

1- Surveillance :-

2- Air Policing :


Another function of an air search

radar system is guiding combat air patrol

(CAP) aircraft to a position suitable to

intercept an enemy aircraft. In the case of

aircraft control, the guidance

information is obtained by the radar

operator and passed to the aircraft by

either voice radio or a computer link to

the aircraft .

3- Missile Control :


The Patriot is an Army surface to air,

mobile, air defense missile system.

Since the mid 1960s, the system has

evolved to defend against aircraft and

cruise missiles, and more recently

against short range ballistic missiles .

OBJECT DETECTION:

Radar is an object-detection system which uses radio waves to

determine the range, altitude, direction, or speed of objects. It can

be used to detect aircraft, ships, spacecraft, guided missiles,

motor vehicles, weather formations, and terrain. The radar dish or

antenna transmits pulses of radio waves or microwaves which

bounce off any object in their path. The object returns a tiny part

of the wave's energy to a dish or antenna which is usually located

at the same site as the transmitter.


OBJECT DETECTION:


Non ambiguous range


W hen discussing about the radar range, a distinction must be made betweenthe non-ambiguous range and the real detection range.The non-ambiguous range is (for a pulsed radar) related to the Pulse Repetition Frequency (PRF, = 1/PRI, Pulse Repetition Interval)A typical radar timing is shown in fig.1: the two transmit pulses (Tx and Tx2) are divided by a time equal to the PRI. Rx1 is the echo from Tx1 reflected by a target placed at "Range A". Rx2 can be either the echo from Tx2 reflected by a target at "Range B" or from Tx1 reflected by a target at "Range C".

Radar Presentation

Technology

Transcript of Radar Presentation