radar unit 5 tracking radars

7/24/2019 Radar Unit 5 Tracking Radars

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1 SINGLE TGT TRACKER (STT) TRACKS A SINGLE TGT AT FAST DATA

RATE.

DATA RATE 10 OBS/SEC. EMPLOYS A CLOSED LOOP SERVO SYSTEM

TO KEEP THE ERROR SIGNAL SMALL.

MISSILE TGTS


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(ADT)

SURVEILLANCE TRACKING RADAR. .

CAN TRACK HUNDREDS/ A FEW

THOUSAND TGTSSIMULTANEOUSLY.

TRACKING IS OPEN LOOP.


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ELECTRONICALLY STEERED PHASED

. LARGE NO OF TGTS CAN BE HELD

ON TRACK.

HIGH DATA RATE (LIKE IN STT)

BEAM IS ELECTRONICALLY

POSITION TO ANOTHER IN A FEW


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SCANS A LIMITED ANGULAR SECTOR TO MAINTAIN

TRACKS SIMULTANEOUS TRACK & SEARCH

DATA RATE : MODERATE

CAN TRACK A NUMBER OF TARGETS.

EQUIVALENT OF TRACK WHILE SCAN IS ADT :

ANGULAR SECTOR, USUALLY IN BOTH AZIMITH &ELEVATION.

,NARROW BEAMWIDTH PENCIL BEAM; OR WITH TWOORTHOGNAL FAN BEAMS (ONE FOR AZIMUTH AND


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AMPLITUDES GIVES THE LOCATION OF THETGT WRT ANT. AXIS.

THE AMPLITUDE AND THE SENSE OF ERRORSIGNAL CAN BE USED TO GENERATE THECORRECTIVE SIGNAL WHICH WITH THE

HELP OF SERVO CONTROL CAN BE USED TO

TARGET ON THE ANTENNA AXIS.

WHEN TGT X-SECTION CHANGES BETWEEN


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TRACKING & RADAR BLOCK DIAGRAM


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SIGN OF O/P OF PHASE SENSITIVEDETECTOR INDICATES THE DIRECTION OFTHE ANGLE ERROR RELATIVE TO THE

.

ANGLE ERROR ; MAGNITUDE IS

PATTERN.

SIGNAL.

FOR DETERMINING THE SIGN OF THEANGLE MEASUREMENT.


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ANGLE TRACKING


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ANGLE TRACKING

BEAM SHOULD BE MOVED TO THE RIGHTTO COINCIDE BORESIGHT & TGT

.

BORESIGHT POSITION 0 IS LOCATED INTHE DIRECTION OF THE TARGET.

THE ABOVE TWO BEAMS ARE SAID TO BE

SQUINTED WITH A SQUINT ANGLE.

BORESIGHT DIRECTION : CROSSOVER OF 2

. AIM IS TO POSITION THE 2 BEAMS SO

THAT = TGT ON THE BORESIGHT


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HYBRID JUNCTIONS

OPERATION DEPENDS ON LENGTHS BETWEEN PORTS AND

HENCE THE DEVICE IS FREQ. SENSITIVE


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TWO COORDINATE MTR (AMP COMPARISON)


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SUM PATTERN : A+B +C +D

AZIMUTH DIFF. PATTERN : (A+B) (C +D)ELEVATION DIFF. PATTERN : (B+D) (A+C)

AGC ENSURES THAT ANGLE ERRORSIGNAL IS NOT EFFECTED BY CHANGESIN SIG. AMPLITUDE.


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LIMITATIONS TO TRACKING ACCURACY

GLINT/ANGLE NOISE/TGT NOISE

RECEIVER NOISE

AMPLITUDE FLUCTUATIONS OF TGT ECHO

OTHERS (MECH PROPERTIES OF ANT,

SERVO SYSTEM ETC) GLINT OCCURS WITH COMPLEX TGTS

WHICH HAVE MORE THAN ONE

ECHOS FROM MULTIPLE SCATTERERS

DIFF. WAVE TILTS.


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GLINT FROM A COMPLEX TGT CAUSES

;RESULTING IN AN ERROR IN THE

GLINT SOMETIMES CAN CAUSE BREAK.

BREAK- TRACK OCCURS WHEN THE

BORESIGHT OF THE TRACKINGANTENNA POINTS OUTSIDE THEANGULAR EXTENT OF THE TARGET.

GLINT IS A MAJOR SOURCE OF ERROR,WHEN MAKING ANGLE MEASUREMENTS,ESPECIALLY AT SHORT RANGES.


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CONICA SCAN (CON - SCAN) & SEQUENTIALLOBING A SINGLE ANTENNA BEAM IS TIME SHARED TO OBTAIN

TIME SHARING A SINGLE ANT. BEAM IS SIMPLER ,USES LESSEQPT THAN SIMULTANEOUS BEAMS BUT IT IS NOT AS

.


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SQUINT ANGLE IT IS THE ANGLEBETWEEN THE AXIS OF ROTATION AND

A TARGET LOCATION

SINCE THE TARGET IS OFFSET FROM THE,CAUSES MODULATION OF THE AMP. OF

TO BEAM ROTATION FREQ.(CONICALSCAN FREQ)


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CONICAL SCAN TRACKING RADAR


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TYPICAL CONICAL SCAN

REV/SEC

THE PLANE OF POLARISATION ROTATING FEED IT CAUSES THE

PLANE OF POLARISATION TO

ROTATE. NUTATING FEED IS PREFERED !!


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COSRO CONICAL SCAN ON

MILITARY CONICAL SCAN AND LOBE

SWITCHING TRACKING RADARS AREVULNERABLE TO ECM, SINCE CONICAL.

A HOSTILE ECM JAMMER CAN DISRUPTCONICAL SCAN TRACKING OF RADAR

RADAR SIGNAL WITH AN AMP.MODULATION THAT IS THE INVERSE OF

.


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COUNTERMEASURE ISCALLED INVERSE GAIN

CONICAL SCAN TRACKING

TRACKING SYSTEMS


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CONICAL SCAN FREQ BY ECM JAMMER) TRACKING RADAR ILLUMINATES THE

TARGET WITH NON SCANING BEAM

AND APPLY CONICAL SCANNING ONRECEIVE ONLY

HENCE THE NAME COSRO

ANALOGOUS OPERATION WITHSEQUENTIAL LOBING IS CALLED LORO


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CONICAL SCAN SEQUENTIAL LOBING.

LOBE SWITCHING ANTENNA PATTERNS


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CONICAL SCAN CONTDTHE DIFFERENCE IN AMPLITUDE BETWEEN

THE VOLTAGES OBTAINED IN THE TWO

SWITCHED POSITIONS IS A MEASURE OFANGULAR DISPLACEMENT OF THE TGTFROM THE SWITCHING AXIS.

THE DIRECTION IN WHICH TO MOVE THE

SIGHT IS FOUND BY OBSERVING WHICH

SIGNAL.


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PULSES BEFORE LOW PASS

THE ENERGY AT THE CONICAL

ANALOG TO DIGITAL CONVERSION.

THIS PULSE STRETCHING IS DONE.


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COMPARED WITH CONICAL SCAN FREQFOR PROPER FILTERING AND AVOIDINGINACCURACY OF THE ANGLE

MEASUREMENT THERE MUST BE ATLEAST 4 PULSES

DURING EACH REVOLUTION OF THE

OBTAIN UP DOWN AND RIGHT-LEFT


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TIMES THAT OF CONICALSCAN FREQUENCY; BUT IT IS

MORE THAN 10 TIMES


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COMPARISON TRACKERS 1. S/N RATIO- IT IS GREATER IN

MONOPULSE RADAR THAN IN CONICAL

SCAN RADAR IT IS BECAUSE IN MONOPULSE,

ANTENNA VIEWS TARGET AT THE PEAK

OF ITS SUM PATTERN. CONICAL SCAN RADAR VIEWS THE TGT

AT SOME ANGLE OFF THE PEAK OF THE

.


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.

MONOPULSE (DUE TO 1) IN

3. COMPLEXIT Y : MONOPULSERADAR IS MORE COMPLEX, DUE

AT THE ANTENNA & 3


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. COMPARISON TRACKERS (contd )

CONICAL SCAN RADAR HAS ONLY ONERECEIVING CHANNEL & USES A SINGLE

.

HOWEVER, DUE TO SOLID STATE AND,

SELDOM A REASON FOR NOT CHOOSING

MONOPLUSE. 4. MINIMUM NO OF PULSES : MONOPULSE

SINGLE PULSE

MINIMUM OF 4 PULSES PER REVOLUTIONOF THE BEAM TO EXTRACT AN ANGLEMEASURMENT IN TWO COORDINATES.


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.

MEASUREMENT AND THEN

MEASUREMENTS TO OBTAIN THE

CONICAL SCAN RADAR, INTEGRATES

,THEN EXTRACTS THE ANGLE


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COMPARISION TRACKERS (CONTD)

.

6 . SUSCEPTIBILITY TO ECM

CONICAL SCAN RADAR IS MORESUSCEPTIBLE TO ECM,

A WELL DESIGNED MONOPULSETRACKER IS MUCH HARD TO DECEIVE.


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-

MONOPULSE TRACKERS ARE USED WHENGOOD ANGLE ACCURACY IS RE UIREDAND

WHEN SUSCEPTIBILITY TO ECM IS TO BEMINIMISED.

APPLICATION CONICAL SCAN

TRACKER IT IS USED BECAUSE OF LOWER COST AND

REDUCED COMPLEXITY.


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MANUAL TRACKING OF

REPLACED BY CLOSED LOOPAUTOMATIC TRACKING,

TRACKER.


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TRACKING IN RANGE


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TRACKING IN RANGE ( CONTD )

LESS THAN THAT OF THE LATE GATE.

THE SIGNALS IN THE TWO GATES ARE

SUBTRACTED TO PRODUCE THE DIFFERENCEERROR SIGNAL

.FAR THE PAIR OF GATES ARE FROM THE

.


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AUTOMATC GAIN CONTROL

: ERROR SENSITIVITY IN SPITE OFAMPLITUDE FLUCTUATIONS OR CHANGES

RANGE AGC SIGNALNEGATIVE DC VOLTAGE

VOLTAGE

CONSTANT ANGLE ERROR SENSITIVITYPROVIDES STABLE TRACKING. AGC AVOIDS SATURATION BY LARGE

SIGNALS

AGC ALSO ATTEMPTS TO REMOVE THE NOISE LIKE AMPLITUDE OF THE TGT ECHO


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AGC (contd)


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AGC (contd)

HOWEVER THE GAIN OF THE AGC

AS TO SUPPPRESS THE ERROR.

THE REQUIRED DYNAMIC RANGE

VARIATION IN RANGE OVER WHICH

EXPECTED VARIATION IN TGT..


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EX : RANGE VARIATION = 40 DB

VARIATION = 40 DB

PARAMETERS = 10 DB

DYNAMIC RANGE (FOR RX AGC)= 90 DB


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A TRACKING RADAR MUST

TARGET BEFORE IT CANOPERATE AS A TRACKER.

CARE TO COVER THE ENTIRE

EFFICIENTLY.


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g a

ANTEENA ISCONTINOUSLY ROTATED

LOWERED IN ELEVATION.


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IT CONSISTS IN RAPID CIRCULAR

AXIS OF THE ANTEENA, COMBINED

THE AXIS OF ROTATION. IT IS

LARGER IN ONE DIMENSION THANANOTHER.


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SPIRAL SCAN (Fig c) :

THIS SCAN COVERS AN ANGULAR SEARCHVOLUME WITH CIRCULAR SYMMETRY.

BOTH SPIRAL SCAN & PALMER SCANSUFFER FROM THE DISADVANTAGE THATALL PARTS OF THE SCAN VOLUME DO

SCANNING SPEED IS VARIED DURING THE.


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IN A UNIFORM MANNER. IT IS A CONVENIENT MEANS

SECTOR, RECTANGULAR IN.


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NODDING SCAN (Fig e) IT IS PRODUCED BY OSCILLATING THE

ANTEENA BEAM RAPIDLY IN ELEVATION.

IT IS USED TO COVER A LIMITED SECTOR

OBTAIN A HEMISPHERICAL COVERAGEELEVATION ANGLE UP TO 900 AND

AZIMUTH SCAN ANGLE UPTO 3600 )

USED IN HEIGHT FINDING RADARS.

radar unit 5 tracking radars

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