Overview of Overview of RADAR ENGINEERINGRADAR ENGINEERING

Prof. N.V.S.N. SarmaDept. of ECENIT,Warangal

:PURPOSE:

1. Detect the presence of an object::

ØIt can detect stationary as well as moving objects.It can also identify the type of object.

2.Detect the speed

ofobjects::

ØThis is the reason why police uses radar to catch the speeders..

3. Mapsomething

ØSatellites useSAR tocreate detailedtopographicmaps ofsurface of planets &moon.

All three of these activities can be accomplished using mainly two concepts::

Ø ECHO.

Ø DOPPLER SHIFT.

1. ECHO::• When you shout into a

well,the sound of your shout travels down the well and is reflected (echoes) off the surface of the water at the bottom of the well. If you measure the time it takes for the echo to return and if you know the speed of sound,you can calculate the depth of the well fairly accurately.

2.Doppler shift::

The person behind the car hears a lower tonethan the driver because the car is moving away.The person in front of the car hears a highertone than the driver because the car isapproaching.

3. APPLICATIONS::1. Air traffic control uses radar to track planes

both on the ground and in the air, and also toguide planes in for smooth landings.

2. Police use radar to detect the speed ofpassing motorists.

3. ISRO uses radar to map the Earth and otherplanets, to track satellites and space debrisand to help with things like docking andmaneuvering.

4. The military uses it to detect the enemy andto guide weapons.

5. Meteorologists use radar to track storms,hurricanes and tornadoes.

3. WHY NOT SOUND WAVES FOR AIR??

Ø Sound doesn't travel very far.

ØDisturbs the neighbours.Ø The echo of the sound would be very

faint, it is likely that it would behard to detect.

The Invention that Changed the World (by Robert Buderi)

Basic Principles• Acronym: RAdio Detection And Ranging

Basic Principles• Radar Classifications

– monostatic vs bistatic vs, etc

– pulsed vs CW– coherent vs incoherent– by frequency band

Band Name Frequency RangeHF 3-30 MHz

VHF 30-300 MHz

UHF 300 MHz-1 GHz

L-band 1-2 GHz

S-band S-band

C-band 4-8 GHz

X-band 8-12.5 GHz

Ku-band 12.5-18 GHz

K-band 18-26.5 GHz

Ka-band 26.5-40 GHz

MMW >34 GHz

Basic Principles• The idea is now to have this transmitted

signal propagate to a target and receive the scattered signal – and learn something!– About the target– About the medium (even if the medium is the

target!)• Details of what we can learn (and how) are

left to other talks – we’ll stick with the basics.

History…History…• New technologies of Radar became available to

Merchant Shipping with the end of hostilities in 1945

• Radar on Merchant Ships was initially installed for commercial purposes– on ferries to maintain better schedules in fog; and– large fishing vessels

• Radar was treated with great suspicion by the mariners…

History…History…

• With improving technology and after sometime the use of Radar for safety purposeswas recognized

• Misinterpretation of Radar information hadnot resulted in any reduction of thenumber of serious collisions at sea

History…History…

• International Conference on Safety of Lifeat Sea in 1960 revised the InternationalRegulations for Preventing Collisions atSea by adding rules to take account of theuse of Radar and recommendations on theuse of Radar information as an aid toavoiding collisions at sea

History…History…

• The International Conference on Safety ofLife at Sea in 1974 adopted provisions tothe SOLAS Convention making Radar amandatory carriage requirement forMerchant Ships in a phased programmestarting in 1980, which finally completed in2002

The Shipmaster’s Point of ViewThe Shipmaster’s Point of View

• The Key Facts are:

– That Radar remains (and will remain) theprimary system for Collision Avoidance; and

– Radar is a very important tool for Navigation

Why is Radar such a valuable tool?Why is Radar such a valuable tool?

• The Master and watch-keepers haveConfidence in information Radar providesbecause:– It’s operation is Ship based– It’s not reliant on third party sources– It has a proven track record– Radar is useful with SARTs when engaged in

search and rescue

In Short…In Short…• In its display, Radar offers the watch-

keepers the basic reality of all targetsrelative to the ship

• It therefore aids the watch-keepers andhelps in decision making for both– Navigation; and– Collision Avoidance

COLLISION AVOIDANCECOLLISION AVOIDANCE

• Early action is required to avoid a closequarters situation, therefore earlyidentification of closing targets is essential

• Watch-keeping officers need to becompetent in the use of Radar and aretrained in its use and the application ofARPA

Some IMO requirements…Some IMO requirements…• Maximum emergency stopping distance

from full speed of the ship should not bemore that 15 ships lengths

• Emergency turn radius of the ship shouldnot be more that 2.5 ships length

Ship parameters…Ship parameters…

• Speed – up to 25 knots• Length

– Largest container ship 335 m– Capesize bulker 300 m– Panamax 220-230 m

Ship parameters…Ship parameters…

• Emergency stopping distance3.3 km – 5 km (1.8 nm – 2.7 nm)

• Emergency turning radius550 m – 840 m (0.3 nm – 0.45 nm)

• Displacement weights 100 000 – 250 000 tonnes

Practical requirementsPractical requirements

• To start plotting targets and determiningtheir course and speed when the target isbetween 8 and 10 nautical miles off

NAVIGATIONNAVIGATION

• Radar gives accurate information ondistance from charted features and assistsin maintaining the ship’s course

• Radar will normally show a 60 metre highland mass at a range of 20 miles. This isconsidered by seafarers as a minimumrequirement

Discrimination of targets from a Discrimination of targets from a watchwatch--keepers perspectivekeepers perspective

• To be able to distinguish a tug from its towat sea at 12 miles range

• Approaching a rig on a supply vessel:• To clearly identify the standby boat from the rig at

6 miles range• To be able to distinguish the anchor pennant

buoys of a semi submersible rig at 3 miles range

NAVIGATIONNAVIGATION

• Radar greatly assists navigation during poor visibility

• Pilots rely on Radar at close range in reduced visibility to pass buoys and beacons.

Typical Radar SpecsTypical Radar Specs

• Power 30-70 kW• Horizontal Beamwidth 0.75 – 4 degrees• Pulse width 0.03 – 1.2 microsec• PRF 4000 – 375 Hz• Noise figure 3 – 8 dB

AntennaeAntennae• Pitch 3 degrees

• Roll 25 degrees

• Yaw 5 degrees

• So vertical beamwidth 20 – 30 degrees

WP 8B 2001WP 8B 2001

Radar Equation

The radar equation provides a relationship between the received power, the characteristics of the target, and characteristics of the radar itself.

The returned power for a single target varies as r-4.

Why?

= 42

2

41

rAPP et

rσ

λπconstant radar

characteristicstarget

characteristics

The returned power for a distributed target varies as r-2

[ ]

ΦΘ= 2

222 )2ln(1024 r

GPcP avgtr

ηλτ

π

constant radarcharacteristics

targetcharacteristics

Radar cross section of an aircraft:

CW/Doppler Radar• Pulsed radar is typically used to detect targets,

determining range and bearing. These radars generally require high-power, are quite complex and thus expensive.

• Continuous wave (CW) radars typically determine target velocity, and can achieve considerable ranges without the high peak power. These radars are typically simpler, more compact and less costly.

OperationOperation

• Must have Relative Motion• Measure Frequency Shift (Doppler)

CharacteristicsCharacteristics

• Duty Cycle = 1 • Ppeak = Pavg

• High SNR• Rmin= 0• Uses 2 antennas

– one transmit and one receive• Basic CW radar cannot measure range!

FMCW Radar

FMCW Radar Source Signal

Frequency varies linearly with time

Snow Surface

Time (ms)0 16 32 48 64

Am

plitu

de

-2

-1

0

1

2

Time (ms)0 16 32 48 64

Freq

uenc

y (G

Hz)

2

3

4

5

6

Why FMCW Radar?

Inexpensive and easy to operateInexpensive and easy to operate

Field portable and robustField portable and robust

Wide bandwidth capabilityWide bandwidth capability

CRREL FMCW Radar

Ku-Band FMCW Radar

25 dB horn25 dB hornHP microwave sourceHP microwave source

LabVIEW data acquisitionLabVIEW data acquisition

Snow Depth Measurements

Ka- and X-band FMCW Radar Experimental Results

Distance (m)0 20 40 60 80 100

Snow

Dep

th (c

m)

0.0

0.2

0.4

0.6

0.8

Manual Probe X-Band FMCW Radar

Ice Channel Detection with Microwave FMCW Radar

ExcavatedIce Channel

Ice Channels

Experiment Setup and Results

Corner Reflectors

Snow Surface

2- 6 GHz FMCW Radar

Radar Detection of Landmines

Snow Covered Test Site Anti-tank Mines in Frozen Ground

Electromagnetic Signature of Snow, Ice and Frozen Ground

CRREL Test FacilityOptical and MMW Radar Data

Multiband Radar Properties of Snow Cover

X-band (8-12 GHz)

Ka-band (26.5-40 GHz)

C-band (3.9-5.9 GHz)

Moving Target IndicatorMoving Target Indicator

Moving Target Indicator

• In the presence high noise and sea clutter, this radar is used to detect only moving objects.

• It differentiates even slow moving targets from stationary objects.

• Its variant for the same purpose is Pulse Doppler Radar

Tracking Radar

• Tracking is a different game all together• The special techniques to track a target

and pinpoint its location , the special techniques needed and the associated challenges are discussed at length.

• The ingenius of way getting all the required information in a single shot is presented.

TRACKING RADAR

69

Radar Transmitter and Receiver

• The engineering and technological aspects of various subsystems and individual circuits both in the transmitter and receiver are discussed .

• The special devices like duplexer and displays are introduced with supportive argument.

Simplified Radar Transmitter/Receiver System Block Diagram

Phased Array Radar

• The most modern radar which can handle multiple tasks at very high speed is unfolded.

• The advantages and limitations are mentioned along with the specialities

• The special techniques involved are introduced.

Phased Array Phased Array

Navigational Aids

• The radars used for navigation of ships and aircrafts are presented along with diagrams and justifications

• All the required background history and evolution is also mentioned.

Methodology• What is navigation• Conventional methods• Electronic methods

– ADF– VOR– DME– ILS

• Future Systems

ADF

ADF Bearing Indicator

Topics to be covered::

• Radar Basics• Radar

Equation• CW Radar• Moving Target

Indicator• Tracking

Radar

• Radar Transmitter and Receiver

• Phased Array Radar

• Navigational Aids

References• Skolnik, M., Introduction to Radar Systems,

New York, McGraw-Hill, 3rd Edition, 2001

• Skolnik, M., Radar Handbook, New York, McGraw-Hill, 2nd Edition, 1990