EE602: RADAR SYSTEMS

Seminar on

Air Traffic Control RADAR

Team Members: Meghanad Shingate (09307608) Ankit Jamod (10307071) Tanmay Sarkar(10307059)

Guided by Prof. Girish P. Saraph Dr. K. P. Ray

ATC RADAR Objectives

To regulate a single airport’s traffic.

To give guidance to aircraft and prevents collisions.

To give accurate and continuous knowledge of aircraft position.

To provide assistance to pilots.

Identification Friend or Foe

Security

ATC Radars

Surface Movement Radar(SMR)

Short Range ground Radars

Terminal Approach Radar(TAR)

Long Range Ground Radars

ATC radar beacon system (PSR & SSR)

Weather Radar

Primary Surveillance Radar (PSR)

PSR operates using traditional radar principle.

PSR are similar to the two dimensional search radar (working in azimuth and range only) and cannot measure altitude.

The advantage PSR is that it operates totally independently of the target aircraft.

Only provide range & direction information.

Secondary Surveillance Radar (SSR)

SSR is a much more accurate that complements the basic PSR.

The SSR is equipped with a main antenna, and an omni-directional antenna.

SSR relies on a piece of equipment on the aircraft known as a 'transponder'.

Interrogations used very specific types of signals (1030 and 1090 MHz)

SSR will detect the identification of the aircraft, the height of aircraft, speed and direction of flight.

Typical Scenario

Block Diagram(SSR)

Transponder

Transponder:( Transmitter-responder)

The transponder send encoded information about the aircraft.

The transponder antenna is low gain so that it can receive and reply to a radar from any direction.

If a plane did not respond correctly the system determined that the target was an unidentified aircraft.

CRITICAL SUBSYSTEM ANTENNA

PSR ANTENNA

Reflector contour shaped - cosecant square shaped pattern.

Improved coverage for elevation angles up to 45°

rapid pattern drop-off below the horizon to eliminate the effects of ground multipath reflection.

Narrow azimuth beamwidth to improve azimuth resolution, accuracy

S-band(2.7-2.9 GHz) Gain . . . . . . . . 32 dB

MTI- Circuit to eliminate ground clutter

SSR ANTENNA

• Vertical array of dipoles suitably fed to produce the desired shape

• Uplink-1.03 Downlink-1.09 GHz

• Gain …………….27 dBi

• Polarization ….Vertical

• Beam-width = Lambda/Dimension in that direction

• No MTI-system needed

ROTATION

RPM ~ q*PRF/N

q = beam-width [degrees]

N= number of pulses that the target is exposed to

RPM = 5-10

SSR Side-Lobe Suppression

• Inhibit the Transponder's reply in response to a side-lobe interrogation.

• Directional antenna + Omni-directional antenna

• P2 decides Interrogation received from the main beam or Side lobe

• P2 pulse greater than P1 pulse no reply

SSR Side-Lobe Suppression

Interference

Interferences

FRUIT(False Replies Un-synchronised wih Interrogator Transmission)

All world wide SSR uses same frequency.

arises from replies, these were triggered not by the own interrogator.

Arise when atleast one target is in main lobe of atleast two interrogators

replies overlapping in time at the receiver antenna

Interference

DEFRUITER:

The aircrafts transponder has to transmit multiple replies.

These replies are stored in the defruiter and compared with each other in the next PRT now.

Reflections

Suppression of unwanted reflections:

SSR radars are often located in the vicinity of buildings with reflecting surfaces

SSR interrogator will form a false target (image)

SOLUTION

Improved Interrogator Side Lobe Suppression (IISLS).

P1- main beam, P2- control pulse

Disables interrogations for 35μs.

References

”Civil Avionics Systems” by Ian Moir & Allan G Seabridge, Professional Engineering Publishing Limited,London, UK.

http://www.radartutorial.eu