Lecture 7a: Radio

Detection And

Ranging(RADAR)

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What is RADAR

• RADAR is stand for Radio Detection And Ranging.

• Radar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft &ships.

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Radar Frequencies

• Radar operates on UHF and SHF - Super High Frequency (1 GHz - 30 GHz)

Why RADAR systems are in a UHF& SHF bands ????

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Radar Frequencies

• RADAR systems are in SHF bands because:

a) These frequencies are free from disturbance.

b) Higher frequency, shorter wavelength, RADAR used more effective.(shorter wavelengths are reflected more efficiently.)

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Radar Frequency Bands• L-Band Radar

– This frequency band (1 to 2 GHz) is preferred for the operation of long-range air-surveillance radars out to 250 NM (≈400 km). Used by En Route Surveillance Radar-RSR

• S-Band Radar– This frequency band (2 to 4 GHz) are used near airports to

detect and display the position of aircraft in the terminal area with a medium range up to 50-80 NM (≈100 km). Used by Terminal Area Radar –TAR

• K- and Ka- Band Radars– This frequency bands (18-40 GHz) provide short range,

very high resolution data. Used by Surface Movement Radar-SMR

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Radar Frequency Band

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RADAR Applications

RADAR has a wide range applications including

1. Ground RADAR : extensively used by ATC to separate aircrafts.1. Primary RADAR: to track the progress of aircraft.

2. Secondary RADAR: similar like primary radar but secondary radar can provide much more information about the target (aircraft)

2. Airborne Weather RADAR: used by pilots. It provide pilots with information regarding weather ahead.

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En-Route Radar Display

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1. GROUND RADAR

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Ground radar

• Ground radar is typically used to fix an aircrafts position which allows ATC to separate aircraft and guide the pilot.

• There are types types of ground radar which are

A) PRIMARY RADAR B) SECONDARY RADAR

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A) Primary RADAR

• Primary RADAR is used to track the progress of aircraft

• Three Primary RADAR systems used by ATC include1. En-Route Surveillance Radar (RSR)2. Terminal Area Radar (TAR)3. Surface Movement Radar (SMR)

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a) En-Route Surveillance Radar (RSR)

• En-Route Surveillance Radars (RSR) are long range radars which the signal goes to 200 to 300 NM.

• It used L-band frequencies (1 to 2 GHZ)

• It used for airway surveillance to provide range and bearing of aircraft.

**Surveillance: close observation, especially of a suspected spy or criminal.

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b) Terminal Area Radar (TAR)

• These are medium range radars, up to 75NM.

• It used S-Band frequencies (2 to 4GHz)

• It is used as an approach aid and for controlling aircraft traffic close to airport area.

• Normally used in conjunction with Secondary Radar.

• **Secondary radar provide additional information such as identification, air speed, direction and altitude of aircraft to assist ATC to track the position of aircraft.

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Terminal Area Radar (TAR)

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c) Surface Movement Radar (SMR)

• SMR is one type of Airport Surface Detection Equipment (ASDE).

• SMR installed at airport (at top of ATC tower building) to provide a very accurate radar display in all weathers and conditions of visibility. (K & Ka-Band frequencies -18-40Ghz)

• SMR radar display can show all of airfield infrastructure including aircraft movements on runway, taxiway and apron.

• It is designed to provide clear display of all aircraft on runway or taxiway so that ATC can ensure runway are clear for take-off/landing and also guide aircraft to apron in order.

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c) Surface Movement Radar (SMR)

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c) Surface Movement Radar (SMR)

• The surface movement radar (SMR) allows the Air Traffic Controller to 'see' in real time the aircraft and vehicles movements into the airport control area.

• Surface movement radar can improve both safety and efficiency of airport traffic by providing the ground controller with a clear picture of the areas or under poor visibility conditions.

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How Primary Radar Works

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How Primary Radar Works

• A radar system (ground-based) has a transmitter that emits radio waves or microwaves signal.

• The signal hit airplane and reflect back.• Ground radar picks up reflected signal during a break

between transmissions.• The time taken for the reflected signal to return back

enables a computer calculate how far the object is (range).

• The aircraft data then sent and shown on a Radar Display monitor by ATC

• Thus, the ATC could know the position of aircraft.

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Most conventional aircraft have a rounded shape. This shape creates a very efficient radar

reflector. Means that no matter where the radar signal hits the plane, some of the signal gets

reflected back

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However, some military aircraft are designed and constructed to be non-reflective - the so-called

“stealth aircraft”.

B-2 Spirit stealth bomber of the U.S Air Force

An F-117 Nighthawk stealth strike aircraft

F-22 Raptor

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A stealth aircraft is made up of completely flat surfaces and very sharp edges. When a radar signal hits a stealth plane, the signal reflects away at an

angle. Surfaces on a stealth aircraft also can absorb radar energy as well. So, this aircraft become

invisible.

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Advantages of Primary Radar

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

• Means that no action from the aircraft is required for it to provide a radar return.

• Only provide range & direction information

Primary Radar

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Disadvantages of Primary Radar

• First, transmitted signal is limited by ‘line of sight’, thus signal can be interrupted by buildings, hills & mountains.

• Second, more power must be radiated to ensure returns from the target.

• Third, because of the small amount of energy returned at the receiver, reflected signals may be easily disrupted. This may cause the displayed target to 'fade‘ (not clear).

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Question Bank1. Radar & It frequencies

a) Define RADAR and give reason why it operates in SHF (Super High Frequency). (6M)

b) In details, describe L-Band, S-Band, K & Ka Band Radars. (9M)

2. Primary Radara) Describe RADAR and its application (3M)

b) Describe the three types of Primary Radar used by ATC. (12M)

3. Primary Radara) Explain how primary radar works & give reason why ‘Stealth’

aircraft can be invisible (9M)

b) Describe advantages & disadvantages of primary radar (6M)

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Group Presentation

• Group 1: DME-Distance Measuring Equipment (Faiz,Syeikh,Rubesha,Vijendran,Zarul)

• Group 2: TCAS-Traffic Collision Avoidance System (Yasser, Padhma, Fairie, Azlina, Girish)

• Group 3: GPWS-Ground Proximity Warning System (Syedi, Aziz, Nantha, Khaliq, Zul Fiqrie, Shafiq)

• Group 4: ALS-Approach Lighting System (Bibiana,Fakhrul,Choy, Kingsley, Syahirul)