Register online at www.ATIcourses.com or call ATI at 888.501.2100 or 410.956.8805 Vol. 97 – 21

April 6-8 2009Columbia, Maryland

$1490 (8:30am - 4:00pm)

"Register 3 or More & Receive $10000 eachOff The Course Tuition."

SummaryThis three-day course examines the atmospheric

effects that influence the propagation characteristics ofradar and communication signals at microwave andmillimeter frequencies for both earth and earth-satellitescenarios. These include propagation in standard,ducting, and subrefractive atmospheres, attenuationdue to the gaseous atmosphere, precipitation, andionospheric effects. Propagation estimation techniquesare given such as the Tropospheric ElectromagneticParabolic Equation Routine (TEMPER) and RadioPhysical Optics (RPO). Formulations for calculatingattenuation due to the gaseous atmosphere andprecipitation for terrestrial and earth-satellite scenariosemploying International Tele-communication Union(ITU) models are reviewed. Case studies are presentedfrom experimental line-of-sight, over-the-horizon, andearth-satellite communication systems. Exampleproblems, calculation methods, and formulations arepresented throughout the course for purpose ofproviding practical estimation tools.

InstructorG. Daniel Dockery received the B.S. degree in physics

and the M.S. degree in electricalengineering from Virginia PolytechnicInstitute and State University. Sincejoining The Johns Hopkins UniversityApplied Physics Laboratory (JHU/APL)in 1983, he has been active in the areasof modeling EM propagation in the

troposphere as well as predicting the impact of theenvironment on radar and communications systems.Mr. Dockery is a principal-author of the propagation andsurface clutter models currently used by the Navy forhigh-fidelity system performance analyses atfrequencies from HF to Ka-Band.

Course Outline1. Fundamental Propagation Phenomena.

Introduction to basic propagation concepts includingreflection, refraction, diffraction and absorption.

2. Propagation in a Standard Atmosphere.Introduction to the troposphere and its constituents.Discussion of ray propagation in simple atmosphericconditions and explanation of effective-earth radiusconcept.

3. Non-Standard (Anomalous) Propagation.Definition of subrefraction, supperrefraction andvarious types of ducting conditions. Discussion ofmeteorological processes giving rise to these differentrefractive conditions.

4. Atmospheric Measurement / SensingTechniques. Discussion of methods used to determineatmospheric refractivity with descriptions of differenttypes of sensors such as balloonsondes, rocketsondes,instrumented aircraft and remote sensors.

5. Quantitative Prediction of Propagation Factoror Propagation Loss. Various methods, current andhistorical for calculating propagation are described.Several models such as EREPS, RPO, TPEM,TEMPER and APM are examined and contrasted.

6. Propagation Impacts on System Performance.General discussions of enhancements anddegradations for communications, radar and weaponsystems are presented. Effects covered include radardetection, track continuity, monopulse trackingaccuracy, radar clutter, and communication interferenceand connectivity.

7. Degradation of Propagation in theTroposphere. An overview of the contributors toattenuation in the troposphere for terrestrial and earth-satellite communication scenarios.

8. Attenuation Due to the Gaseous Atmosphere.Methods for determining attenuation coefficient andpath attenuation using ITU-R models.

9. Attenuation Due to Precipitation. Attenuationcoefficients and path attenuation and their dependenceon rain rate. Earth-satellite rain attenuation statisticsfrom which system fade-margins may be designed.ITU-R estimation methods for determining rainattenuation statistics at variable frequencies.

10. Ionospheric Effects at MicrowaveFrequencies. Description and formulation for Faradayrotation, time delay, range error effects, absorption,dispersion and scintillation.

11. Scattering from Distributed Targets. Receivedpower and propagation factor for bistatic andmonostatic scenarios from atmosphere containing rainor turbulent refractivity.

12. Line-of-Sight Propagation Effects. Signalcharacteristics caused by ducting and extremesubrefraction. Concurrent meteorological and radarmeasurements and multi-year fading statistics.

13. Over-Horizon Propagation Effects. Signalcharacteristics caused by tropsocatter and ducting andrelation to concurrent meteorology. Propagation factorstatistics.

14. Errors in Propagation Assessment.Assessment of errors obtained by assuming lateralhomogeneity of the refractivity environment.

Propagation Effects for Radar and Communication Systems

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OUTLINE

• Part 1: Over-Sea Propagation

• Part 2: Scalar Parabolic Equation (PE) Algorithms

• Part 3: Over-Land Propagation

• Part 4: 3-D Vector PE Modeling

Part 1 Outline:Over-Sea Propagation

• Introduction & Radar Equation• Surface Reflection• Multipath• Rough Sea Effects• Spherical Earth Diffraction & Radio Horizon• Physical Optics Models• Atmospheric Refractivity• Atmospheric Measurements• Evaporation Ducting• Synoptic Weather Factors• Sea Clutter• HF Propagation

Radar EquationWe begin by reviewing the basic monostatic radar range equation describing received power for a radar system:

2 4

3 4(4 )t t r RCS

rPG G PFP

r Lλ σπ

=

Where Pt = Transmitted powerGt = Transmit antenna gainGr = Receive antenna gainλ = Radar wavelengthPF = Pattern Propagation Factorr = Slant range from radar to targetσRCS = Target radar cross section (RCS)L = Miscellaneous system losses

Path LossAnother quantity frequently used to describe propagation effectsis path loss (PL). The relation between PF and PL is

22

2 2(4 )PL PF

rλπ

=

This quantity is most useful for one-way communications problems, where the transmission equation can be written in terms of PL as

22

2(4 )r t t r

t t r

P PG G PFr

PG G PL

λπ

=

=

The results presented in this course will generally be presented in terms of PF2 or PF4.

Multipath Geometry“Flat Earth”

Earth’s Surface

θ =-θg

Source

θg

SpecularlyReflectedField

“Direct”Field

θr

r2r1

r’=r1+r2

-30 -25 -20 -15 -10 -5 0 5

0 20 40 60 800

100

200

300

400

500

range [km]

heig

ht [m

]Multipath, 3 GHz, zs = 20 m V-pol

Alti

tude

(m)

PF2 (dB)

0 20 40 60 80-60

-50

-40

-30

-20

-10

0

10

range [km]

PF2 [d

B]

Multipath, 3 GHz, zs = 20 m at height = 200 m

H-polV-pol

Earth Horizon Geometry

Rh

zob

zs

Source

Target

Earth

Hei

ght (

m)

-50 -40 -30 -20 -10 0 10

-50 -40 -30 -20 -10 0 10

0 20 40 60 80 1000

100

200

300

400

500

range [km]

heig

ht [m

]4/3 earth horizon, zs = 20 m, V-pol 3 GHz

0 20 40 60 80 100-50

-40

-30

-20

-10

0

10

range [km]

PF2 [d

B]

4/3 earth horizon, zs = 20 m, V-pol at height = 200 m

10 GHz 3 GHz 1 GHz 500 MHz

Horizon = 76.8 km

Effective Earth Radius (k-factor)

ae

keff ae

h

h'

keff is such that h=h' at each range when ray is drawn straight. Sinceray curvature depends on refraction,keff also depends on refractive conditions.

Propagation ConditionsHorizontally Launched Rays

Subrefraction dN/dz>0

Free Space dN/dz=0

SuperrefractiondN/dz<-39

Standard dN/dz=-39

Ducting Threshold dN/dz=-157

Ducting dN/dz<-157

Earth

0 20 40 60 80 100-50

-40

-30

-20

-10

0

10

range [km]

PF2 [d

B]

4/3 earth horizon, zs = 20 m, V-pol, 3 GHz at height = 200 mPhysical Optics Regions

Interference RegionBold

InterpolationRegion

DiffractionRegion

Propagation Factor (dB)

Range (nmi)

Physical Optics – PE Comparison3 GHz, 100-ft Antenna Altitude, V-Pol.Standard Atmosphere, 500 ft Altitude

Atmospheric refraction has a large effect on system performance –The “standard atmosphere” assumption is often inadequate

EvaporationDuct

Alti

tude

“Standard”Atmosphere

“4/3

Ear

th”

“M” = Modified Refractivity M

0-40m

SurfaceDuct

M

50-500m

ElevatedDuct

M

0.2-2km

Sub-refraction

M

0-300 m Ducting Ducting LayerLayer

UpwardUpward--Refracting Refracting

LayerLayer

TYPES OF REFRACTIVE CONDITIONS

red = strongest

illumination

Alti

tude

Range

Little affect

on surface sensors

Strong Surface-Based Ducting

Measured Surface-BasedDuct Profile

Standard Atmospherekeff = 1.33

One-Way Propagation Factor F2

– S-Band– 50-foot Antenna – Narrow Beamwidth

Sin(x)/x Pattern

Circulation Associated with Sea-Breeze

15-25 nm

Rising Air Due to Surface Heating

Warm Dry Sinking

< 3,000 feet

Dry Hot

Water

LandCool Moist

Sea Breeze

15-25 nm

This situation results in the over-water conditions persisting some distance inland

Advection Off Shore

15-25 nm

Dry Hot Continental Air

Water

LandCool Moist Marine Air

Off-Shore Flow

15-25 nm

This situation results in a surface duct increasing in height away from shore

Helicopter Instrumentation• Usual Aircraft: Bell Jet or Long Ranger• Crew: Civilian Pilot & 2 APL Engineers• Custom APL Instrumentation

IR Sea Temp “Fast” T,RH

Pitot Static Sensor: Air speed

Compass “Slow” T, RH

InstrumentedHelicopter

Shipboard Radars

Helicopter Vertical Profiles

~600 m

10 km

Helo Data Sample collected September 2001 Near Camp Pendleton, CA

STDLand

• Measured Environment (first profile only)

• Measured Environment (all profiles)

Propagation Diagram

Clutter Power EquationIgnoring propagation effects, the monostatic radar equation for received clutter power by a pulsed radar may be written as

2 2 4

3 3(4 ) 2t

r o BPG f cP

rλ τσ θ

π⎛ ⎞= ⎜ ⎟⎝ ⎠

where G is the antenna gain assumed for both transmit & receive, f 4 is the two-way antenna pattern factor in the direction of the surface, c is the speed of light, θB is the azimuth beamwidth, and τ is the pulse width. This is the equation that has historicallybeen inverted to estimate σo using data from clutter measurement campaigns. Thus, in empirically based models for σo, the propagation effects are embedded in the normalized cross section.

Sea Clutter GeometryMonostatic Pulsed Radar

cτ /2θg

θB

cτ secθg /2

rθB

zs

SPANDAR Sea ClutterDate Date

HF Propagation Mode Diagram

Earth

Surface Wave

Ground Wave

Sky Wave

Ionosphere

Ionosphere Effects Summary

Effect Freq. Dep.

0.5 GHz

1 GHz 3 GHz 10 GHz

Faraday Rotation (deg) 1/f2 432 108 12 1.1Propagation Delay (µsec) 1/f2 1 0.25 0.028 0.0025Excess Range Delay (m) 1/f2 300 75 8.3 0.75

Refraction (‘ or “) 1/f2 <2.4’ <0.6’ <4.2” <0.36”RMS Dir. Of Arrival (“) 1/f2 48” 12” 1.32” 0.12”

Absorption (auroral/polar) (dB)

~1/f2 0.2 0.05 0.006 5x10-4

Absorption (mid-latitude) (dB)

1/f2 <0.04 <0.01 <0.001 <10-4

Dispersion (psec/Hz) 1/f3 0.004 0.0005 1.9x10-5 5x10-7

Scintillation (dB) >20 ~10 ~4

TEC=1.86x1018 m-1 ; B=0.43 Gauss ; Angle through ionosphere=30 deg

Part 2 Outline:Scalar PE Algorithms

• Summary of Modeling Approaches• Vector & Scalar Wave Equations• Parabolic Wave Equations• Numerical Solution Approaches• Basic and Mixed Fourier Split Step Solutions• Source Modeling• Surface Roughness• Validation Examples

Part 3 Outline:Propagation Over Terrain

• Introduction• Primary Terrain-related Effects• Propagation Modeling Approaches• Modeling Propagation Over Terrain With

PE Models• Refractivity Characteristics• Land Clutter

Part 4 Outline:3-D Vector PE Modeling

• Introduction

• 3-D Scalar PE Approaches (Brief Summary)

• 3-D Vector PE Modeling

• Modeling Propagation Over Terrain

• RCS Calculations (Brief Summary)

Boost Your Skillswith On-Site CoursesTailored to Your NeedsThe Applied Technology Institute specializes in training programs for technical

professionals. Our courses keep you current in the state-of-the-art technology that isessential to keep your company on the cutting edge in today’s highly competitivemarketplace. For 20 years, we have earned the trust of training departments nationwide,and have presented on-site training at the major Navy, Air Force and NASA centers, and for alarge number of contractors. Our training increases effectiveness and productivity. Learnfrom the proven best.

ATI’s on-site courses offer these cost-effective advantages:

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We suggest you look at ATI course descriptions in this catalog and on the ATI website.Visit and bookmark ATI’s website at http://www.ATIcourses.com for descriptions of allof our courses in these areas:

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I suggest that you read through these course descriptions and then call me personally, JimJenkins, at (410) 531-6034, and I’ll explain what we can do for you, what it will cost, and whatyou can expect in results and future capabilities.

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