George W. Stimson introduction to Airborne Radar (Se)

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563

Rules of Thumb

It is said that the instant way to become a radar expert is

to learn a few rules of thumb. While that is absurd, it is

true that most radar experts repeatedly use a number of

very simple rules of thumb. And these can be just as use-

ful to you.

Antenna Beamwidth

You can remember these rules most easily by keeping in mind (a) that

the null on either side of the boresight line of a linear array occurs at an

angle

for which the difference in distance from the observer to the ends

of the array equals one wavelength

, and (b) that the 3dB beamwidth is

roughly half the null-to-null.

Note: λ and L must be in the same units.

Appendix

To apply these rules to any wavelength, λ, multiply

dB by λ/3.

Antenna Gain

You can remember these rules most easily by thinking of antenna gain as equal

to the ratio of (a) the area of a sphere of unit radius(A=4p) to (b) the area that

is marked off on this sphere by a solid angle corresponding to the 3dB width of

the antenna beam.

To apply these to any wavelength, λ, multiply L, W, and d by 3/λ.

Bandwidth

Note: If

ot T are in seconds, BW is in hertz.

Reference Data

UNITS OF SPEED

1 foot/sec

0.59248 knot

0.681818 stat. mph

1.09728 kilometers/hr

1000 fps ; 0.59248 knot

1 kilometer/hr

0.539957 knot

0.621371 stat. mph

0.277777 meters/sec

0.911344 ft/sec

1 knot*

1.15078 stat. mph

1.85200 kilometers/hr

1.68781 feet/sec

*A knot is 1 nautical mile per hour

APPENDIX

564

Doppler Shift (at X-band)

35 hertz per second

(actually 34.30)

30 hertz per statute mile per hour

19 hertz per kilometer per hour

20 kilohertz per 1000 feet per second

To apply these rules to any wavelength, λ, multiply by 3λ

Filter Passband

Frequency, Wavelength, Period

Pulse Length

1000 ft/

s of pulse width

500 radar ft/

s of pulse width

Round-Trip Ranging Times

12.4

s per nautical mile

10.7

s per statute mile

6.7

s per kilometer

Range

Units of Measure

1 radian 5 57.3°

3 cm. ' 0.1 ft.

1 nmi ; 6000 ft.

APPROXIMATE SPEED OF SOUND (MACH 1)

Sea Level 36,000 to 82,000 ft.*

1230 km/hr

Decreases

1062 km/hr

765 mph Linearly 660 mph

665 knots

To ⇒

573 knots

*Above 82,000 feet, the speed increases linearly to 1215 km/hr

(755 mph, 656 knots) at 154,000 ft.

SPEED OF LIGHT*

299,792.4562 kilometers/s

' 300 3 10

meters/sec

;

300 3 10

meters/sec

;

300 3 10

meters/sec

;

300 3 10

meters/sec

; 300 3 10

meters/sec

*In a vacuum.

APPENDIX

565

RADIO FREQUENCY BANDS

Designation Frequency Wave Length

HF 3–30 MHz 100m–10m

VHF 30–300 MHz 10m–1m

UHF 300-3000 MHz 1m-10cm

SHF 3–30 GHz 10cm-1cm

EHF 30–300 GHz 1cm–1mm

Microwaves: ; 1m–1cm

Millimeter waves: ; 1cm-1mm

THE RADAR BANDS

Designation Assigned Frequencies*

VHF 138 – 144 MHz

216 – 225 MHz

UHF 420 – 450 MHz

890 – 942 MHz

L 1215 – 1400 MHz

S 2300 – 2500 MHz

2700 – 3700 MHz

C 5250 – 5925 MHz

X 8500 – 10,680 MHz

Ku 13.4 – 14.0 GHz

15.7 – 17.7 GHz

K 24.05 – 24.25 GHz

Ka 33.4 – 36.0 GHz

*Bands specifically assigned for radar used by the

International Telecommunications Union, ITU.

DECIMAL MULTIPLIER PREFIXES

Prefix Symbol Multiplier

giga G 10

mega M 10

kilo k 10

milli m 10

–3

micro

–6

nano n 10

–9

UNITS OF LENGTH

1 inch

2.540 centimeters

0.1 foot

;

3 centimeters

1 foot

30.4800 centimeters

1 yard

0.914400 meters

1 meter

1.09361 yards

3.28083 feet

39.3701 inches

microns

1 kilometer

0.539957 naut. mile

0.621371 stat. mile

1093.61 yards

3280.83 feet

1 statute mile

0.868976 naut. mile

1.60934 kilometers

1760 yards

5280 feet

1 nautical mile

1.15078 stat. miles

1.85200 kilometers

2025.37 yards

' 2000 yards

6076.12 feet

BASIC TRIGONOMETRIC IDENTITIES

sin (A 1 B) 5 sin a cos B 1 cos A sin B

sin (A 2 B) 5 sin a cos B 2 cos A sin B

cos (A 1 B) 5 cos a cos B 2 sin A sin B

cos (A 2 B) 5 cos a cos B 1 sin A sin B

EQUIVALENCY SYMBOLS

Symbol Meaning (as used in this book)

∝

Proportional

; Roughly equivalent

' Approximately

;

Nearly equal

5 Equal

566

References

“A View of Current Status of Space-Time Processing Algorithm

Research,” H. Wang et al., IEEE International Radar

Conference, pp. 789-791.

“Aircraft-Borne Interferometric SAR for 3-D High Resolution

Radar Imaging,” H. D. Griffiths, C. J. Baker, A. Currie, R. Voles,

R. Bullock, and P. V. Brenna; IEE Colloquium Digest 1994.

“An Overview of Space-Time Adadptive Processing for Airborne

Radars,” Hong Wang, Dept. of Electrical Engineering and

Computer Science, Syracuse University, 1997.

Radar Handbook, second edition, M. Skolnik, McGraw-Hill,

1990.

“Rapid Convergence Rate in Adaptive Arrays,” I. S. Reed, J. D.

Mallett, L. E. Brennan; IEEE Transactions on Aerospace and

Electronic Systems, vol. AES-10, no. 6, Nov. 1974.

“Real-Time Adaptive Airborne MTI, Part I: Space-Time

Processing,” R. Klemm; Proc. ICR 96, Oct. 1996.

“Switched Fiber-Optic Delay Architectures,” Akis P. Goutzoulis,

D. Kenneth Davies; Photonic Aspects of Modern Radar, chap. 13,

Artech House.

“Theory and Design of Interferometric Synthetic Aperture

Radars,” E. Rodriguez, J.M. Marin; IEEE Proceedings-F, vol. 139,

no. 2, April 1992.

INDEX

Index Terms Links

567

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“A ” display 21

A/D converter:

avoiding saturation 250

quantization noise 250

dynamic range 249

general concept 28 247

spurious signals 249

sampling rates, representative 552

Active ESA 474 550

Active ESA design:

array physical design 489

chip set 487

module efficiency 489

monolithic microwave ICs 487

phase and amplitude control 489

power output 488

receiver noise figure 488

stick architecture 489

tile architecture 490

transmitter noise 488

VLICs 487

Active missile guidance 43

Advanced waveforms:

monopulse doppler 521

pulse burst 520

range-gated high PRF 519

search-while -track 523

AH-64D helicopter 558

Air (power)strip line 486

Air-combat modes 551 553

Air-to-air search 42 335 383

Air-to-ground surveillance 41 549

Air-to-sea search 45

Air-traffic -control beacons 37

Alert 506

Altimeters 37

INDEX

Index Terms Links

568

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Altitude return 302

Amplitude modulator 63

AMRAAM missile 43 523 550 532

AMTI:

general 11

clutter-referenced 24

clutter canceller 547

Analog doppler filtering 239

AND gate 538

Angle deception:

cross polarization 452

crosseye 450

double cross 453

terrain-bounce 450

Angle measurement:

lobing 102

monopulse 103

Angle off boresight (AOB) 387

Angle track on jamming 458

Angle tracking:

angle discriminant 387

angle off boresight (AOB) 387

antenna stabilization 387

coordinate systems 387

filter 387

tracking loop 386

Antenna, angular resolution 101

Antenna beam steering:

electronic 100

mechanical 100

Antenna beams:

cosecant squared 106

fan 106

pencil 91

INDEX

Index Terms Links

569

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Antenna characteristics:

aperture efficiency 98

beamwidth 96

effective area 98

gain 98

main lobe 92

radiation pattern 91 105

sidelobes 99

angular resolution 101

Antenna phase center 317

Antenna RCS reduction:

antenna mode reflections 494

avoiding Bragg lobes 496

edge diffraction 494

edge treatment 495

frequency-selective screen 497

ground plane 493

random scattering 494 495

reflections, planar array 493

structural-mode reflections 494

validation 497

Antenna servo 22

Antenna sidelobe reduction 99

Antenna stabilization 387

Antenna types:

parabolic reflector 95

planar array 95 551 553

APG-68 radar 551

APG-73 radar 552

APG-76 radar 554

APG-77 radar 550

APN-241 radar 559

APQ-164 radar 556

APQ-181 radar 555

APS-145 early warning radar 547

APY-2 radar 548

INDEX

Index Terms Links

570

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Atmospheric attenuation 87

absorption 87

scattering 87

Automatic gain control (AGC):

application of 552

digital 360

long time constant 444

medium PRF for 359

wide dynamic range, for 505

Automatic tracking:

single-target tracking 22 383

search-while -track 523

track-while -scan 8 388

AWACS radar 548

B display 20 21

B-1B bomber 556

B-2 bomber 555

Backscattering coefficient 294

Bandwidth:

instantaneous 503

total 503

Bar (search scan) 5

Beam steering:

electronic 100

mechanical 100

Bin masking:

range 445

velocity (doppler) 445

Binary phase modulation 169

Bipolar video signal 28

Blind landing guidance 40

Blind tactical bombing 44

Blip (target) 20

Boltzmann ’s constant 118

Boresight line 92

Bragg lobes 496

INDEX

Index Terms Links

571

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Built-in self test (BIST) 541

Bulk memory, global 540

C-130 559

Carrier frequency 66 108

Chaff:

bandwidth 440

employment 439

RCS 440

Chirp 163

CIP (see also Integrated processing) 550

Circuit polarization 55 556

Clock rate (processor) 543

Cluster (processor modules) 540

Cluster controller 540

Clutter canceller 341 344

Clutter filters 29

Coherence 10 202

Collision-avoidance 37

Command-inertial guidance 43

Common integrated processor 542 550

Complex operator “W ” 271

Conical scan 9

Cooley-Tukey FFT 275

Cooling option 543

Corporate feed 485

COTS 541 542 554

Counter countermeasures (ECCM) 439

Countermeasures (ECM) 457

Cross-range resolution 393

Crosseye deception 450

Crossbar switch 537

Dark Star (unmanned stealth aircraft) 546

Data processor 30

Data security 543

Data transfer 543

INDEX

Index Terms Links

572

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dB (decibels):

as absolute units 77

advantages 73

basic power ratios 74 75

power ratio conversion 74 75

definition of 71

in terms of voltage 77

gain/loss 76

power ratios <1 75

Decoys:

expendable 453

Luneberg lens 454

towed 453

Detection range:

ambient noise 86

Boltzman's constant 118

CFAR 127

detection process 125

determining factors 115

false-alarm 126

false-alarm probability 126

false-alarm rate 127

matched filter design 120

mean noise energy 120

mean noise power 120

noise energy 120

noise from ahead of receiver 119

postdetection integration 131

predetection integration 127

radar cross section (RCS) 122

receiver noise figure 116

receiver noise measurement 117

target-signal energy 122

Dielectric strip line 486

Differentiating signal from noise 70