157131901 tutorial de radares

7/27/2019 157131901 Tutorial de Radares

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„Radartutorial“ (www.radartutorial.eu)

Radartutorial

Book 2 „Radar Sets“

Preamble:

Radar systems come in a variety of sizes and have different performance specifications.Some radar systems are used for air-traffic control at airports and others are used for long-range surveillance and early-warning systems. radar system is the heart of a missileguidance system. Small porta!le radar systems that can !e maintained and operated !y oneperson are availa!le as well as systems that occupy several large rooms.

Table of Contents:Radartutorial ......................................................................................................................................... 1

"ream!le# ....................................................................................................................................... $%a!le of &ontents# .......................................................................................................................... $'earning (!)ectives# ....................................................................................................................... $

Classification of Radar Systems (1) .................................................................................................... 2*maging Radar + ,on-*maging Radar ........................................................................ 2

"rimary Radar ................................................................................................................................ 2"ulse Radar .................................................................................................................................... 2

"ulse Radar using "ulse &ompression ..................................................................... onostatic + Bistatic Radars ......................................................................................

Secondary Radar ............................................................................................................................

"rinciple of operation ................................................................................................ &omparison "rimary Radar vs. Secondary Radar ..................................................... /

&ontinuous 0ave Radar ................................................................................................................. /

Block 1iagram of an &0-Radar ................................................................................ Speed gauges ...........................................................................................................

3re4uency odulated &0 radar ................................................................................................ Classification of Radar Sets (2) ........................................................................................................... 6

ir-defense Radars .................................................................................................................... 5

................................................................................................................................. 678amples of Battlefield Radars ....................................................................................................... 6

0eapon &ontrol Radar ........................................................................................ 6ulti 3unction Radars ............................................................................................... 6ulti- %arget %racking Radar .................................................................................... 6ortar 'ocating Radar ........................................................................................ 9

ir %raffic &ontrol :%&; Radars ............................................................................................... 9

7n Route Radars ...................................................................................................... 9 ir Surveillance Radar :SR; .................................................................................... 9

"recision pproach Radar :"R; .............................................................................. 9Surface ovement Radar :SR; .............................................................................. 9Special 0eather-Radar pplications ......................................................................... 9

Radar Frequency ands ...................................................................................................................... !

"earnin# $b%ecti&es:

%his !ook gives an overview a!out the wide range of radar systems. %he student shouldknow the differences !etween primary and secondary radars and can e8plain !oth theadvantages and disadvantages of these two different radar systems.

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.; $



3igure 2# monopulse secondary surveillance radarantenna :looks like a lattice fence; mounted on top of an

antenna of a primary radar :para!olic reflector;


Classification of Radar Systems (1)1epending on the desired information< radar sets must have different 4ualities andtechnologies. (ne reason for these different 4ualities and techni4ues radar sets areclassified in#

3igure $# Radar systems classified according to specific function

'ma#in# Radar on*'ma#in# Radar

*maging radar sensors measure two dimensions of co-ordinates at least for a calculating of amap-like picture of the area covered !y the radar !eam. n imaging radar forms a picture ofthe o!served o!)ect or area. *maging radars have !een used to map the 7arth< other planets<asteroids< other celestial o!)ects and to categorize targets for military systems.

,on-imaging sensors take measurements in one linear dimension< as opposed to the twodimensional representation of imaging sensors. %ypically implementations of a non-imagingradar system are speed gauges and radar altimeters. %hese are also called scatterometerssince they measure the scattering properties of the o!)ect or region !eing o!served. ,on-imaging secondary radar applications are immo!ilizer systems in some recent private cars.

Primary Radar

"rimary Radar transmits high-fre4uency signals which are reflected at targets. %he arisenechoes are received and evaluated. %his means< unlike secondary radar sets a primary radarunit receive its own emitted signals as an echo again. "rimary radar sets are fitted with anadditional interrogator as secondary radar mostly< to com!ine the advantages of !othsystems.

Pulse Radar

"ulse radar sets transmit a high-fre4uencyimpulse signal of high power. fter this impulsesignal< a longer !reak follows in which the echoescan !e received< !efore a new transmitted signalis sent out. 1irection< distance and sometimes ifnecessary the height or altitude of the target can!e determined from the measured antennaposition and propagation time of the pulse-signal.%hese classically radar sets transmit a very shortpulse :to get a good range resolution; with ane8tremely high pulse-power :to get a good

ma8imum range;.

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.; 2



3igure # simple !lock diagram of secondary surveillance radar


Pulse Radar usin# Pulse Com+ression

%hese radar sets transmit a relatively weak pulse with a longer pulse-width. *t modulates thetransmitting signal to o!tain a distance resolution also within the transmitting pulse with helpof the pulse-compression.

,onostatic istatic Radarsonostatic radars are deployed in a single site. %ransmitter and receiver are collocated andthe radar uses the same antenna mostly.

Bistatic radar consists of a separated :!y a considera!le distance; transmitting and receivingsites.

Secondary Radar

t secondary radar sets the airplane must have a transponder :transmitting res+onder ; on!oard and this transponder responds to interrogation !y transmitting a coded reply signal.%his response can contain much more information< than a primary radar unit is a!le toac4uire :7.g. an altitude< an identification code or also any technical pro!lems on !oard suchas a radio contact loss ...;.

Princi+le of o+eration

%he interrogator on the ground transmits coded pulses with different modes. 7very moderepresents a different 4uestion. 3or conventional SSR :i.e. not mode-S; the choice of4uestions is very simple. %he controller wants to know the identity of the aircraft :„0ho areyou>?;. %he Radar gives a 2 dimensionalposition fi8 of the aircraft< !ut air trafficcontrol is very much a dimensionalprocess< so „0hat height are you>?completes the positional fi8. %hese

different 4uestions determine the (17of operation. %he aircrafts transponderreply with a &(17.

%he chosen mode is encoded in the&oder. :By the different modes different4uestions can !e defined to theairplane.; %he transmitter modulatesthese coded impulses with the R3fre4uency. Because another fre4uencythan on the replay path is used on theinterrogation path< an e8pensiveduple8er can !e renounced. %heantenna is usually mounted on theantenna of the primary radar unit :as shown in 3igure 2; and turns synchronously to thedeflection on the monitor therefore.

receiving antenna and a transponder are in the airplane. %he receiver amplifies anddemodulates the interrogation impulses. %he decoder decodes the 4uestion according to thedesired information and induces the coder to prepare the suita!le answer. %he coderencodes the answer. %he transmitter amplifies the replays impulses and modulates thesewith the R3 reply-fre4uency.

gain in the interrogator on the ground# %he receiver amplifies and demodulates the replayimpulses. @amming or interfering signals are filtered out as well as possi!le at this.

3rom the information „ode? and „&ode? the decoder decodes the answer. %he display of theprimary radar represents the additional interrogator information. "erhaps additional num!ersmust !e shown on an e8tra display.

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.;



4 2

1 1; PSR SSR

tx tx P P R R

: :

74n. $# two-way free-space path loss !y "SRversus one-way free-space path loss !y SSR


Com+arison Primary Radar &s. Secondary Radar

Primary Sur&eillance Radar (PSR)

%he primary radar unit has a ma)or4uality# *t works with passive echoes.

%he transmitted high-fre4uencyimpulses are reflected !y the targetand then received !y the same radarunit. 0ell< direct cause of thereflected echo is the transmittingimpulse sent out !y the radar unit.

Secondary Sur&eillance Radar (SSR)

Secondary radar units work according to anotherprinciple# %hese work with active answer signals.

%he secondary radar unit transmits and alsoreceives high-fre4uency impulses< the so calledinterrogation. %his isnAt simply reflected< !ut received!y the target !y means of a transponder whichreceives and processes. fter this the targetanswers with another fre4uency< the responsetelegram which is produced and transmitted.

Both systems have advantages and disadvantages due to the different principles. *f one winssafe information a!out direction< height and distance of the targets with the primary radar<then the secondary surveillance radar still provides additional information< like signalidentification and also the altitude of the targets.

%he cooperation of the target :transponder; isnecessary to reach a drastic reduction of thetransmit power in case of the same ma8imumrange. Because the transmit power influencesthe radar e4uation at the primary radar withthe two way travel< at the secondarysurveillance radar only one way. factor $CCC as a guide value can !e assumed. 3rom this a su!stantially simpler< smallerand cheaper transmitter follows. %he receiver can !e more insensitive< since the power of theactive answers is higher than the power of the passive echoes. %his circumstance adverselyaffects< however< the influence of the side lo!es. %his must !e compensated !y usingsuita!le measures of the side lo!e suppression.

Since the transmitting fre4uency and receiving fre4uency are different< no clutterdistur!ances arise. ,o %*-system therefore is needed to the compensation of groundclutter. (n the other hand a fre4uency change is impossi!le !y )amming. Specialdistur!ances at secondary radar e4uipments make additional wiring measures necessary.

Continuous -a&e Radar

&0 radar sets transmit a high-fre4uency signal continuously. %he echo signal is receivedand processed permanently too. %he transmitted signal of these e4uipments is constant inamplitude and fre4uency. %hese e4uipments are specialized in speed measuring. 7.g. thesee4uipments are used as speed gauges of the police. (ne has to resolve two pro!lems withthis principle#

• prevent a direct connection of the transmitted energy into the receiver :feed!ackconnection;<

• assign the received echoes to a time system to !e a!le to do run time measurements.

direct connection of the transmitted energy into the receiver can !e prevented !y#

• spatial separation of the transmitting antenna and the receiving antenna< e.g. the aimis illuminated !y a strong transmitter and the receiver is located in the missile flyingdirection towards the aimD

• fre4uency dependent separation !y the 1oppler-fre4uency during the measurementof speeds.

run time measurement isnAt necessary for speed gauges< the actual range of the delin4uentcar doesnAt have a conse4uence. *f you need range information< then the time measurementcan !e realized !y a fre4uency modulation or phase keying of the transmitted power. &0-radar transmitting a unmodulated power can measure the speed only !y using the 1oppler-effect. *t cannot measure a range and it cannot differ !etween two reflecting o!)ects.

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.; /



3igure 5# Ranging with a 3&0 system

3igure /# Schematic diagram of a &0 1oppler- Radar

3igure # Speed gaughe“%raffipa8 Speedo"hot “ :R(B(% Eisual Systems=m!F;


loc /ia#ram of an C-*Radar

Simple &0 1oppler- Radar sets have adesign shown in 3igure .

%he generator generates very sta!le R3-

3re4uency f s. second generatorgenerates the *3-fre4uency f ZF . mi8erstage with a following narrow!and filtergenerates the sta!le local-oscillator-fre4uency f s+f ZF as sum of thetransmitterGs fre4uency and a generated*3-fre4uency. s a part of thesuperheterodyne receiver the ne8t mi8erstage converts the !ackscattered R3-signals f s+f D to the *3- fre4uency. %he *3-amplifier makes the receiver very sensitive for the weak echo signals. %he output of the lastmi8er stage is the 1oppler-fre4uency f D only. %he fre4uency counter counts the 1oppler-

fre4uency and !y means of this counted value calculates the speed. *n order to o!tain aprecise result< this calculation procedure must !e cali!rated in accordance !y an e8actlyspecified radiation angle to the carriageway.

S+eed #au#es

Speed gauge is a very specialized &0-radar. %ransmittingunmodulated power it can measure the speed only !y using the1oppler- effect. *t cannot measure a range and it cannot differ!etween two reflecting o!)ects. run time measurement isnAtnecessary for speed gauges< the actual range of the delin4uent cardoesnAt have a conse4uence. *f you need range information< thenthe time measurement can !e realized !y a fre4uency modulation

or phase keying of the transmitted power.

Since the value of the 1oppler- fre4uency depends on thewavelength< these radar sets use a very high fre4uency !and.3igure shows the speed gauge „%raffipa8 Speedophot?. %his radaroperates at fre4uency of 2/.$2 gigahertzGs.

*t can measure the speed of the incoming and the outgoing traffic< from the right or left !orderof the street. %he radar can !e mounted in a car or on a tripod. %he traffic offence can !ecircumstantiated !y a photo camera with high resolution.

Frequency ,odulated C- radar

&0 radars have the disadvantage that they cannotmeasure distance< !ecause there are no pulses to time.*n order to correct for this pro!lem< fre4uency shiftingmethods can !e used. *n the fre4uency shifting method<a signal that constantly changes in fre4uency around afi8ed reference is used to detect stationary o!)ects.0hen a reflection is received the fre4uencies can !ee8amined< and !y knowing when in the past thatparticular fre4uency was sent out< you can do a range calculation similar to using a pulse. *tis generally not easy to make a !roadcaster that can send out random fre4uencies cleanly<so instead these 3re4uency-odulated &ontinuous 0ave radars :3&0;< use a smoothly

varying „ramp? of fre4uencies up and down. Similar to pulse radars the measured delay timecan !e used for calculating the range !y the following e4uation#

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.;



3igure 9# 1iagram of a typical 21-Radar< therotating cosecant s4uared antenna pattern

3igure H# 1iagram of a typical 1-Radar< ami8 of vertical electronic !eam steering andmechanically horizontal movement of apencil-!eam


0

2

c t R

∆⋅

=0here# c 0 I speed of light I J$C9 m+s

Δt I measured time-difference KsLR I distance altimeter to terrain KmL :2;

%his kind of radar is used as 0radar altimeter? often. %he radar altimeter is used to measure

the e8act height during the landing procedure of aircraft. Radar altimeters are also acomponent of terrain avoidance warning systems< telling the pilot that the aircraft is flying toolow or that terrain is rising to meet the aircraft.

Classification of Radar Sets (2)Radar systems may !e divided into types !ased on the designed use. %his section presentsthe general characteristics of several commonly used radar systems#

3igure 6# &lassification of radar sets according its use

lthough any and every radar can !e a!used as military radar< the necessary distinction asmilitary or civil radar has legal causes often.

ir*defense Radars

ir-1efense Radars can detect air targets and determinetheir position< course< and speed in a relatively largearea. %he ma8imum range of ir-1efense Radar cane8ceed CC miles< and the !earing coverage is acomplete 5C-degree circle. ir-1efense Radars areusually divided into two categories< !ased on the amountof position information supplied. Radar sets that provideonly range and !earing information are referred to astwo-dimensional< or 21< radars. Radar sets that supplyrange< !earing< and height are called three-dimensional<or 1< radars.

ir-1efense Radars are used as early-warning devices!ecause they can detect approaching enemy aircraft ormissiles at great distances. *n case of an attack< earlydetection of the enemy is vital for a successful defenseagainst attack. ntiaircraft defenses in the form of anti-aircraft artillery :a!!reviated to „?;< missiles< or fighterplanes must !e !rought to a high degree of readiness intime to repel an attack. Range and !earing information< provided !y ir-1efense Radars<used to initially position a fire-control tracking radar on a target.

nother function of the ir-1efense Radar is guiding com!at air patrol :&"; aircraft to aposition suita!le to intercept an enemy aircraft. *n the case of aircraft control< the guidanceinformation is o!tained !y the radar operator and passed to the aircraft !y either voice radioor a computer link to the aircraft.




3igure $$# Felicopter and ircraft Radio1etection :FR1; in the =erman7ngagement &ontrol- Search- and

c4uisition system

3igure $C# ntenna of a mo!ile 1-ir-1efense Radar<


a)or ir-1efense Radar pplications are#

• 'ong-range early warning :including air!orne earlywarning< 70;

• Ballistic missile warning and ac4uisition

• Feight-finding

•

=round-controlled interception :=&*;

3am+les of attlefield Radars

-ea+on Control Radar

Radar that provides continuously position data on a singletarget is called tracking radar. ost tracking radar systemsused !y the military are also fire-control radarD the twonames are often used interchangea!ly.

%ypical fire-control radar characteristics include a very highpulse repetition fre4uency :"R3;< a very narrow pulse

width< and a very narrow !eam width. %hesecharacteristics< while providing e8treme accuracy< limit therange and make initial target detection difficult.

3ire-control radar must !e directed to the general locationof the desired target !ecause of the narrow-!eam pattern.%his is called the designation phase of e4uipmentoperation. (nce in the general vicinity of the target< theradar system switches to the ac4uisition phase ofoperation. 1uring ac4uisition< the radar system searches asmall volume of space in a prearranged pattern until thetarget is located. (nce the target is located< the radar system enters the track phase of

operation. Msing one of several possi!le scanning techni4ues< the radar systemautomatically follows all target motions. %he radar system is said to !e locked on to the targetduring the track phase. %he three se4uential phases of operation are often referred to asmodes and are common to the target-processing se4uence of most fire-control radars.

,ulti Function Radars

ctive array ulti-3unction Radars :3Rs; ena!le modern weapon systems to cope withsaturation attacks of very small radar cross-section missiles in a concentrated )ammingenvironment. Such 3Rs have to provide a large num!er of fire-control channels<simultaneous tracking of !oth hostile and defending missiles and mid-course guidancecommands.

%he active phased-array antenna comprises flat sensor panels consisting of arrays of =asmodules transmitting varia!le pulse patterns and !uilding up a detailed picture of thesurveillance area. typical fi8ed array configuration system could consist of a!out 2<CCCelements per panel< with four fi8ed panels. 7ach array panel can cover HCN in !oth elevationand azimuth to provide complete hemispherical coverage.

,ulti* Tar#et Tracin# Radar

(perational functions of a ulti- %arget %racking Radar :%%R; include#

• long-range searchD

• search information with high data rate for low-flying aircraftD

• search information with high resolution of close in air targetsD

• automatic position and height informationD

• simultaneous tracking of a lot of aircraft targetsD

• target designation facilities for other systems.




3igure $2# "rinciple of mortarlocating radar

3igure $# SR7-6<a typically en-routeradar

3igure $/# SR-$2< atypically ir SurveillanceRadar

3igure $# "R-9C< atypically "recision

pproach Radar

3igure $5# SRScanter 2CC$


,ortar "ocatin# Radar

ortar 'ocating Radar provides 4uick identification to pinpointenemy mortar positions in map co-ordinates< ena!ling artilleryunits to launch counter attacks. %he system electronically< scansthe horizon over a given sector several times a second<

intercepting and automatically tracking hostile pro)ectiles< thencomputing !ack along the tra)ectory to the origin. %he co-ordinates and altitude of the weapon are then presented to theoperator.

ir Traffic Control (TC) Radars

%he following ir %raffic &ontrol :%&; surveillance< approach and landingradars are commonly used in ir %raffic anagement :%;#

• en-route radar systems<

• ir Surveillance Radar :SR; systems<

• "recision pproach Radar :"R; systems<• surface movement radars< and

• special weather radars.

n Route Radars

7n-route radar systems operate in '-Band usually. %hese radar sets initiallydetect and determine the position< course< and speed of air targets in arelatively large area up to 2C nautical miles :,;.

ir Sur&eillance Radar (SR)

irport Surveillance Radar :SR; is approach control radar used to detectand display an aircraftAs position in the terminal area. %hese radar setsoperate usually in 7-Band< and are capa!le of relia!ly detecting andtracking aircraft at altitudes !elow 2<CCC feet :6<52C meters; and within /Cto 5C nautical miles :6 to $$C km; of their airport.

Precision ++roac4 Radar (PR)

%he ground-controlled approach is a control mode in which an aircraft isa!le to land in !ad weather. %he pilot is guided !y ground control usingprecision approach radar. %he guidance information is o!tained !y theradar operator and passed to the aircraft !y either voice radio or acomputer link to the aircraft.

Surface ,o&ement Radar (S,R)

%he Surface ovement Radar :SR; scans the airport surface to locate thepositions of aircraft and ground vehicles and displays them for air trafficcontrollers in !ad weather. Surface movement radars operate in @- to O-!and and uses an e8tremely short pulse-width to provide an accepta!lerange-resolution. SR are part of the irport Surface 1etection 74uipment:S17;.

S+ecial -eat4er*Radar ++lications

0eather radar is very important for the air traffic management. %here are weather-radarsspecially designed for the air traffic safety.




3igure $9# Some radars and its fre4uency !and


Radar Frequency ands%he spectrum of the electric magnetic waves shows fre4uencies up to $C2/ Fz. %his verylarge complete range is su!divided !ecause of different physical 4ualities in differentsu!ranges.

%he division of the fre4uencies to the different ranges was competed on criteria formerly<which arose historically and a new division of the wave!ands which is used internationally isout-dated and arose so in the meantime. %he traditional wave!and name is partly still used inthe literature< however. n overview shows the following figure#

3igure $6# 0aves and fre4uency ranges used !y radar.

%here are two different significant radar fre4uency letter-!and nomenclatures in use. (nesystem uses a more historically originated system of letters and is defined even as an *777-Standard. %hese letter designations were originally selected to descri!e the secret radar!ands used in 0orld 0ar **. ilitary Radar-applications in ,%( uses another nomenclaturewith easier a!ecedarian letters. %his system allows an easy e8tension with higherfre4uencies and is originally devised for conducting electronic support measures<countermeasures and electronic warfare< and :at least military; radars are an important partof it. %he !oundaries of the fre4uency !ands are distri!uted nearly logarithmical.

Since without that the correctfre4uency is known< a

transformation isnAt alwayspossi!le into the newerwave!ands with ,%(-nomenclature. (ften in themanufacturers documents arepu!lished the traditionalwave!ands. %he differentdesignations for Radar-3re4uency Bands are veryconfusing. %his is no pro!lemfor a radar engineer ortechnician. %hey can handle

with these different !ands<fre4uencies and wavelengths. %he pro!lem is nowto assert< that a fre4uencygenerator for * and @-Bandserves the O- and Pu-BandRadars and the 1-Band@ammer interferes an '-BandRadar.

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.; H




Radar systems work in a wide !and of transmitted fre4uencies. %he higher the fre4uency of aradar system< the more it is affected !y weather conditions such as rain or clouds. But thehigher the transmitted fre4uency< the !etter is the accuracy of the radar system.

* and * and (5F* and 5F* Radar)%hese radar !ands !elow CC Fz have a long historically tradition !ecause these

fre4uencies represented the frontier of radio technology at the time during the 0orld 0ar **.%oday these fre4uencies are used for early warning radars and so called (ver %he Forizon:(%F; Radars. Msing these lower fre4uencies it is easier to o!tain high-power transmitters.%he attenuation of the electro-magnetic waves is lower than using higher fre4uencies. (n theother hand the accuracy is limited< !ecause a lower fre4uency re4uires antennas with verylarge physical size which determines angle accuracy and angle resolution. %hese fre4uency-!ands are used !y other communications and !roadcasting services too< therefore the!andwidth of the radar is limited :at the e8pense of accuracy and resolution again;.%hese 3re4uency !ands are currently e8periencing a come!ack< while the actually usedStealth technologies donAt have the desired effect at e8tremely low fre4uencies.

C* and (75F* Radar)

%here are some specialized Radar sets developed for this fre4uency !and :CC to$ =Fz;. *tis a good fre4uency for the operation of radars for the detection and tracking of satellites and!allistic missiles over a long range. %hese radars operate for early warning and targetac4uisition like the surveillance radar for the edium 78tended ir 1efense System:71S;. Some weather radar-applications e.g. wind profilers work with these fre4uencies!ecause the electromagnetic waves are very low affected !y clouds and rain.

%he new technology of Mltrawide!and :M0B; Radars uses all fre4uencies from - to &-Band. M0B- radars transmit very low pulses in all fre4uencies simultaneously. %hey areused for technically material e8amination and as =round "enetrating Radar :="R; forarchaeological e8plorations.

/* and ("*and Radar)

%his fre4uency !and :$ to 2 =Fz; is preferred for the operation of long-range air-surveillanceradars out to 2C , :Q/CC km;. %hey transmit pulses with high power< !road !andwidth andan intrapulse modulation often. 1ue to the curvature of the earth the achieva!le ma8imumrange is limited for targets flying with low altitude. %hese o!)ects disappear very fast !ehindthe horizon.

*n ir %raffic anagement :%; long-range surveillance radars like the ir RouteSurveillance Radar :RSR; works in this fre4uency !and. &oupled with a onopulseSecondary Surveillance Radar :SSR; they use a relatively large< !ut slower rotatingantenna. %he designator '-Band is good as mnemonic rhyme as large antenna or longrange.

F*and (S*and Radar)

%he atmospheric attenuation is higher than in 1-Band. Radar sets need a considera!lyhigher transmitting power than in lower fre4uency ranges to achieve a good ma8imum range. s e8ample given the edium "ower Radar :"R; with a pulse power of up to 2C 0. *nthis fre4uency range the influence of weather conditions is higher than in 1-!and. %hereforea couple of weather radars work in 7+3-Band< !ut more in su!tropic and tropic climaticconditions< !ecause here the radar can see !eyond a severe storm.

Special irport Surveillance Radars :SR; are used at airports to detect and display theposition of aircraft in the terminal area with a medium range up to C5C , :Q$CC km;. n SR detects aircraft position and weather conditions in the vicinity of civilian and militaryairfields. %he designator S-Band :contrary to '-Band; is good as mnemonic rhyme as smallerantenna or shorter range.

8* and (C*and Radar)*n =- Band there are many mo!ile military !attlefield surveillance< missile-control and groundsurveillance radar sets with short or medium range. %he size of the antennas provides an

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.; $C




e8cellent accuracy and resolution< !ut the relatively small-sized antennas donAt !other a fastrelocation. %he influence of !ad weather conditions is very high. %herefore air-surveillanceradars use an antenna feed with circular polarization often. %his fre4uency !and ispredetermined for most types of weather radar used to locate precipitation in temperate zonelike 7urope.

'9* and (* and ;u* and Radars)*n this fre4uency-!and :9 and $2 =Fz; the relationship !etween used wave length and sizeof the antenna is considera!ly !etter than in lower fre4uency-!ands. %he *+@- Band is arelatively popular radar !and for military applications like air!orne radars for performing theroles of interceptor< fighter< and attack of enemy fighters and of ground targets. very smallantenna size provides a good performance. issile guidance systems at *+@- !and are of aconvenient size and are< therefore< of interest for applications where mo!ility and light weightare important and very long range is not a ma)or re4uirement.

%his fre4uency !and is wide used for maritime civil and military navigation radars. Eery smalland cheap antennas with a high rotation speed are ade4uate for a fair ma8imum range and agood accuracy. Slotted waveguide and small patch antennas are used as radar antenna<

under a protective radome mostly.%his fre4uency !and is also popular for space !orne or air!orne imaging radars !ased onSynthetic perture Radar :SR; !oth for military electronic intelligence and civil geographicmapping. special *nverse Synthetic perture Radar :*SR; is in use as a maritime air!orneinstrument of pollution control.

;* and (;* and ;a* and Radars)%he higher the fre4uency< the higher is the atmospheric attenuation. (therwise theachieva!le accuracy and the range resolution rise too. Radar applications in this fre4uency!and provide short range< very high resolution and high data renewing rate. *n % theseradar sets are called Surface ovement Radar :SR; or irport Surface 1etection74uipment :S17;. Msing of very short transmitting pulses of a few nanoseconds affords a

range resolution< that outline of the aircraft can !e seen on the radars display.*andBy the molecular dispersion :here this is the influence of the air humidity;< this fre4uency!and stay for a high attenuation. Radar applications are limited for a short range of a coupleof meters here.

-*andFere are two phenomena visi!le# a ma8imum of attenuation at a!out 6 =Fz and a relativeminimum at a!out H5 =Fz. Both fre4uency ranges are in use practically. *n automotiveengineering small !uilt in radar sets operate at 665 =Fz for parking assistants< !lind spotand !rake assists. %he high attenuation :here the influence of the o8ygen molecules (2;enhances the immunity to interference of these radar sets.

%here are radar sets operating at H5 to H9 =Fz as la!oratory e4uipments yet. %heseapplications give a preview for a use of radar in e8tremely higher fre4uencies as $CC =Fz.

uthor# &hristian 0olff< graduated Radar engineer< SSgt. =..3. :Rtd.; $$

157131901 tutorial de radares

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