Lecture 01

Lecture 1Lecture 1

EE‐871: Antennas and Wave Propagation DR. RASHID AHMAD BHATTI

Lecture 1: OUTLINE

Introduction to the Course

Introduction to the Antenna Technology

Research Directions in the Field of Antenna Designg

Review of EM Theory (Maxwell’s Equations and BCs)

Radiation Mechanism

EM Wave Scattering and PropagationEM Wave Scattering and Propagation

EE‐871: Antennas and Wave Propagation

Introduction to the CourseEE-871: Antennas and Wave PropagationEE 871: Antennas and Wave Propagation

Instructor: Dr Rashid Ahmad BhattiInstructor: Dr. Rashid Ahmad BhattiE-mail: [email protected] No. : 0321-8580322

Recommended Texts: Antenna Theory: Analysis and Design, By C.A. Balanis,Published by Wiley, 1982.

Radio Wave Propagation and Antennas: An Introduction, By John Griffiths, Prentice-Hall, 1987., y , ,

Tentative Grading Policy:

Mid-Term Exam: -Homeworks: -Final Exam:Final-Exam: -



Course OutlineIntroduction to the Antenna Technology:Introduction to the Antenna Technology:

Fundamental Parameters of Antennas: HW # 1

Radiation Integrals and Potential Functions: HW # 2

Wire Antennas:

Loop Antennas:

Slot Antennas: HW # 3

Frequency Independent Antennas:

Mid-Term Exam

Printed Antennas: HW # 4Printed Antennas: HW # 4

Array Antenna Theory: HW # 5

Aperture Antennas: HW # 6

Numerical Techniques in EM: HW # 7

Antenna Measurement Techniques:

Wave Propagation: HW # 8

Final Exam



General InstructionsSubmit your homeworks within specified time

Plagiarized home work will get zero marks.

You can use software of your choice to solve assigned homeworks (Matlab, Mathcad etc).

Any software can be used for the analysis of antenna structures (CST, HFSS, NEC etc)


Antenna Technology

Antenna Definition“Part of a transmitting or receiving system that is designedPart of a transmitting or receiving system that is designedto radiate or to receive electromagnetic waves”.

A t i t t th t id t iti b tAntenna is a structure that provides transition betweenguided and free-space waves.

50 Ω 377 Ω


50 Ω 377 Ω

Antenna Technology: Brief History

1873- Unification of the theories of electricity and magnetism by Maxwell.

1886- First Radiation experiment by Hertz: Spark was generated through a dipole antenna, and it was detected in the gap of a loop antenna.

1901- Marconi sent signals across the Atlantic.

Till 1940s- wire antennas only up to UHF.

WWII- New antenna elements were invented (slot, horn, reflector).( , , )

Post WWII- 1960s – 1990s: Computer technology revolutionized antenna engineering Numerical methodsantenna engineering….Numerical methods.

Modern Era: Numerical methods powered by computer clusters; MOM, FDTD FEM High Frequency Methods and Hybrid Techniques


FDTD, FEM, High Frequency Methods, and Hybrid Techniques.

Antenna Technology: Brief History

H t A tHertz Antenna

Marconi Antenna


Antenna Technology: EM Spectrum


Antenna TechnologyClassification of Antennas

Geometry: Wire Antennas

Beam Shape:Omni-directional

Applications:

Aperture Antennas P i t d A t

Pencil beamFan beamShaped beam

RadarsCommunicationsSatellitesPrinted Antennas Shaped beam SatellitesElectronic WarfareEMI/EMC

Gain:Low Gain

Bandwidth:Narrow band

EMI/EMCAntenna Test FacilitiesRFID

Medium GainHigh Gain

WidebandMultiband

BiomedicalGPRRadio Astronomy


Radio Astronomy

Antenna Technology: General Antenna Systems

Radar Antennas



Radio Astronomy Antennas

The Jicamarca Radio Observatory to Study Ionosphere

Located away from civilizations to avoid noise from the transmittersLocated away from civilizations to avoid noise from the transmitters.


Antenna Technology: EMI/EMC Antennas

30 MHz to 200 MHz

30 MH t 3 GH200 MH t 1 GH 30 MHz to 3 GHz200 MHz to 1 GHz

700 MHz to 18 GHz9 kHz to 30 MHz 26 MHz to 6 GHz


Antenna Technology: Std. Antennas for Antenna Measurements

Standard Gain Quad-Ridge Dual Polarized Antenna


Probes for near-field antenna measurements


Communication and EW Antennas



RFID Tag Antennas:



Antenna System on a Typical Large Passenger Aircraft:



Antenna System on a Typical Fighter Aircraft:

Band 3 Aft Array

Band 2 Fwd ArrayUHF Coms

VHF Coms Localizer

Band 3 Aft ArrayBand 4 Aft Array

Band 3 Fwd Az ArrayBand 4 Fwd Az Array

Band 4 Fwd El ArrayBand 2 Aft Array IFDL

Radar ESA

L-BandGPS (CRPA)

Band 2 Fwd Array

Band 4 Fwd El ArrayBand 4 Fwd Az Array

Band 3 Fwd Az ArrayUHF ComsVHF Coms Antennas on lowerside (not shown)

-Lower L-band


Band 2 Fwd Array

LocalizerBand 4 Aft ArrayBand 3 Aft Array

-ACMI-Glide Slope-Marker Beacon-S-band


Wireless Communication Antennas

00X (198

3)orola Dynatac

800

Moto


Antenna Technology: Terminal Antennas

Trends:

Personalization

Globalization

Multimedia Services

Multi‐Dimensional Networks

Reconfigurable Systems

Cellular band (over 5‐bands)

• GSM 4‐band + WCDMA 3‐band • CDMA/PCS diversity • Speaker or mechanic integrated

Low frequency Multimedia

• T‐DMB / ISDB‐T/CMMB • DVB‐H • FM (Active antenna solution)

High frequency Non‐Cell. band

• GPS • Bluetooth •WiBro


Speaker or mechanic integrated • Hand/Head/SAR/HAC req.

( )• LTE (Long Term Evolution)

WiBro•Mobile WiMAX

Antenna Technology: Terminal Antennas

Trends in the Terminal Antenna Design

• Size ReductionSize Reduction

• Light Weight

• Compactness

• Low Profile

• Robustness

• Flexibilityy

• Low Cost

• Durable

Wid b d/M ltib d• Wideband/Multiband

• Low SAR

• High Efficiency

• Multi‐Antenna Systems

• Two Polarization ComponentsSuccessful development of small mobile terminal greatly depends on the antenna technology.

Degraded antenna performances can not be compensated by rest of


Degraded antenna performances can not be compensated by rest of the electronics in a mobile terminal

Antenna Technology: Emerging Antenna Technologies

• Reconfigurable /Tunable Antennas • Reduced RCS Antennas

• UWB Antennas

• Conformal Antennas

• High Gain Wideband Omni‐Dir. Antennas

• Decoupling Wideband Antennas

• MIMO Antennas

• Reflect Array Antennas

• Wideband Low Profile CP Antennas

• Phased Array Antennas

• Nano Antennas

• Fractal Antennas

• Antenna Optimization using GA

• Meta‐material based antennas

• Adaptive Phased Array Antennas

• Pattern Reconfigurable Antennas

• High Impedance Surfaces

• Multiband frequency selective services

• Compact Multiband Antennas

• LF Antennas for Portable Devices

q y


REVIEW OF BASIC EM THEORYTheory of EM fields is based on Maxwell’s Equations

The vectors E, D, H, B are used for electric field [V/m], electric flux density [C/m2], magnetic field [A/m] and magnetic flux density [Weber/m2], respectively.

Th t d ( ti l b ) dThe parameters σ, ε, and μ(non‐negative real numbers) are used as constitutive parameters of the medium under interest, and they are respectively the conductivity [S/m] permittivity (dielectricare, respectively, the conductivity [S/m], permittivity (dielectric constant) [F/m] and permeability (magnetic constant) [H/m].

A medium is called to be "simple" when (i) it is homogeneous, (ii) linear, and (iii) isotropic, and in a simple medium EM vectors are l t d t h th d l t th it ti t d it

EE‐871: Antennas and Wave Propagation Dr. R. A. Bhatti

related to each other and also to the excitation current density.

REVIEW OF BASIC EM THEORY


REVIEW OF BASIC EM THEORY


REVIEW OF BASIC EM THEORYθMaxwell’s Equations in Differential Form

r

∂∂

−=×∇tBEr

rFaraday’s Law

+∂∂

−=×∇ JtDHr

rAmpere’s Law

0=∇

=⋅∇

B

Dr

rρ Coulomb‐Gauss’s Law

Gauss’s Law0=⋅∇ B Gauss s Law

“One of the most penetrating intellects of all time”R A Millik N b l L tR.A. Millikan, Nobel Laureate

“Maxwell’s importance in the history of scientific thought is comparable to Einstein’s (whom he inspired) and to Newton’s (whose influence he curtailed).”


Ivan Tolstoy, Biographer of James Clerk Maxwell

REVIEW OF BASIC EM THEORYGauss’s Law


REVIEW OF BASIC EM THEORYBoundary Conditions

Finite Conductivity Media

n

0→was21 EErr

=

( ) 0ˆ 12 =−× EEnrr “The tangential components of the electric field across an

interface between two media with no impressed magnetic current densities along the boundary of the interface are


continuous”


Finite Conductivity Media0

n∫∫∫ ⋅

∂∂

−=⋅S

dsBdlE

0

yΔxΔ

∫∫∫ ∂ 00

SC t

0ˆˆ ΔΕΔΕ xaxarr

S0C021 =Δ⋅Ε−Δ⋅Ε xaxa xx

tt 21 0=Ε−Εrr

( )rr

0Stt 21 Ε=Ε

rr

( ) 0ˆ 12 =−× EEnrr

“The tangential components of the electric field across an interface between two media with no impressed magnetic current densities along the boundary of the interface are


continuous”



HHrr

( ) 0ˆ 12 =−× HHnrr

“The tangential components of the magnetic field across an interface between two media, neither of which is a perfect conductor and there are no sources, are continuous”

tt HH 21 =

( ) 012× HHn ,

( ) 0ˆ DDrr “The normal components of the electric flux desnsity across an ( ) 012 =−⋅ DDn interface between two media, neither of which is a perfect

conductor and there are no sources, are continuous”

( )EEn 1122 0ˆrr

rr

εεε =−⋅

“The normal components of the electric field intensity across an interface bet een t o media neither of hich is a perfect

nn EE 21

21

rr

εε

= interface between two media, neither of which is a perfect conductor and there are no sources, are discontinuous”




( ) 0ˆ 12 =−⋅ BBnrr “The normal components of the magnetic flux density across an

interface between two media, neither of which is a perfect conductor and there are no sources, are continuous”

( )HHn 0ˆrr

μμ =−⋅ ( )nn HH

HHn

22

1

1122 0rr μ

μμ

=

=−⋅

“The normal components of the magnetic field intensity across an

nn 21

1 μ

p g yinterface between two media, neither of which is a perfect conductor and there are no sources, are discontinuous”



In the presence of surface current along the interface



In the presence of surface charge along the interface


REVIEW OF BASIC EM THEORYBoundary Conditions One Medium is PEC


REVIEW OF BASIC EM THEORYBoundary Conditions One Medium is PEC


REVIEW OF BASIC EM THEORYAdditional Boundary Conditions

d d i hi h d i iFor good conductor i.e. high conductivity


REVIEW OF BASIC EM THEORYSignification of the BCs.

Maxwell’s equations are partial differentialequations. Their solutions will contain integrationconstants that are determined from the additionalinformation supplied by boundary conditions so thateach solution will be unique for each given problem.


REVIEW OF BASIC EM THEORYTime Harmonic EM Fields:

If time variations are of sinusoidal form the fieldsIf time variations are of sinusoidal form, the fieldsare called Time Harmonic EM fields.

The time harmonic variations are represented as tje ω

( ) ( )[ ]jwtezyxEtzyx ,,Re;,, =Ε ( ) ( )[ ]jwtezyxBtzyx ,,Re;,, =ΒFrom Faraday’s Law:

( )[ ] ( )[ ] ( ) ⎥⎦⎤

⎢⎣⎡−=−=×∇ tjtjtj e

dtdzyxBezyxB

dtdezyxE ωωω ,,Re,,Re,,Re

( ) [ ] ( ) [ ]tjtj ωω( ) [ ] ( ) [ ]tjtj ezyxBjezyxE ωω ω ,,Re,,Re −=×∇

( ) ( )zyxBjzyxE ,,,, ω−=×∇


( ) ( )yjy ,,,,

REVIEW OF BASIC EM THEORYMaxwell’s Equations in Time Harmonic Form:

−=×∇ BjErr

ω dj ↔ω+−=×∇ JDjH

jrr

ω dtj ↔ω

=⋅∇ D

jr

ρIn physics, it is common to use

tie ω−

0=⋅∇

∇

B

Dr

ρ Faraday’s law:

BiErr

ω=×∇0=⋅∇ B BiE ω×∇

EE‐871: Antennas and Wave Propagation Ref: Antenna Theory; Analysis and Design by C.A. Balanis

REVIEW OF BASIC EM THEORYRadiation Mechanism

Uniformly distributed charge in a circular cross‐section cylinder (single wire)Uniformly distributed charge in a circular cross section cylinder (single wire)

zvz vqJ =

zss

IvqJ =

zz

zlz

dvdIvqI =

zlz

lz

ddI

aqdt

qdt

==

zlz

lz alq

dtdvlq

dtdIl ==


Radiation Mechanism


Curved Wire

Ref: Antenna Theory; Analysis and Design by C.A. Balanis

Radiation Mechanism

Bent Wire Discontinuous Wire

Terminated Wire Truncated Wire


Radiation MechanismNarrow Band and Wideband Radiation

i i id l f f h d di i i lA continuous sinusoidal waveform of current or charge produces radiation at single frequency (zero bandwidth).

A l ti l th i d id b d di ti Sh t th l idthA pulse propagating along the wire produces wideband radiation. Shorter the pulse width, broader will be the frequency spectrum.

Direction of Propagation


Radiation MechanismRadiation Due to Bends in Conductors

vvva ab Δ=

−=

ttta

ab Δ=

−=

rrvv

rr

vv

vv

ba

Δ=Δ⇒

Δ=

Δ=

ΔCharge accelerates at conductor

rvav

trLim

trrv

tva

t

2

0=⇒=

ΔΔ

⇒ΔΔ

=ΔΔ

=→Δ

bends.Small radius, r, produces high acceleration and results in high l l f di ti


rttrt t 0 ΔΔΔ →Δ level of radiation.

REVIEW OF BASIC EM THEORYRadiation Mechanism:

Vector Wave Equation:

tJ

tEE

∂∂

=∂∂

−∇ μμε 2

22

Time varying current, J, causes the E‐field to change both in time and space It tells us how

EH

tt

∂∇

∂∂ change both in time and space. It tells us how the distortion in the EM field is launched.

In the region of space around the wire, we h d

HE

tH

∂∇

∂∂

=×∇ ε can set the conduction current, J=0.

Since the current is defined as the velocity of charge the derivative of current is equal to

tE

∂−=×∇ μ charge, the derivative of current is equal to

the acceleration of charge.

Propagation EquationsPropagation Equations

These equations tells us that whenever we have acceleration of charge, we create propagating electromagnetic fields.


p p g g g

Two Wires; Source, TL, Antennas, and E-Field Lines

Antenna and E-Field Lines Antenna and Free Space Wave

Source

Antenna

Transmission Line


Radiation MechanismDetachment of E‐Field Lines from a Short Dipole


Radiation MechanismCurrent Distribution on a Two‐Wire Line and Linear Dipole


Radiation MechanismCurrent Distribution on a Linear Dipole

λ<<l2/λl

For small angles:

( )sin 2 2kl kl2/λ=l

( )

2/3λλ << l 2/3λλ << l


2/2/ λλ << lRef: Antenna Theory; Analysis and Design by C.A. Balanis

Radiation MechanismCurrent Variation as a Function of Time for Half‐Wavelength Dipole

/0=t 8/Tt = 4/Tt =

Multiplied by cos(wt)

8/3T 2/Tt


8/3Tt = 2/Tt =


EM Wave Scattering & PropagationEM waves scatter when a change occur in EM boundary conditions. Some characteristic wave phenomena are listed as follows:characteristic wave phenomena are listed as follows:

Specular reflection: This is a mirror‐like reflection, where Snell's law of reflection and refraction is valid Lobes occur due to diffractionrefraction is valid. Lobes occur due to diffraction.

Diffraction: Occur along discontinuities, where EM boundary conditions must be satisfied. Mainly, edge and tip diffractions are of interest.satisfied. Mainly, edge and tip diffractions are of interest.

Traveling wave : A long thin body with near nose‐on illumination may cause these waves. Along the body, EM scattering may occur due to surface discontinuity, change g y, g y f y, gin material (e.g., metal to plastic end of body).

Creeping wave : Waves that propagate in the shadow region of smooth bodies are called creeping waves.

Ducting: Also known as trapped waveguide modes. It occurs when a wave is trapped


inside semi‐open regions, such as an air inlet cavity of a jet.


EM Wave Scattering & PropagationHigh Frequency Asymptotics (Analytical Methods)

GO: Geometric Optics (plane wave reflection + refraction)GO: Geometric Optics (plane wave, reflection + refraction)

GTD: Geometric Theory of Diffraction (GO+ diffraction)

PO: Physical Optics (surface currents, reflection + refraction + Uniform diffraction)O ys ca Opt cs (su ace cu e ts, e ect o e act o U o d act o )

PTD: Physical Theory of Diffraction (surface currents, PO + non-uniform diffraction)

Numerical TechniquesFDTD: Finite Difference Time Domain (direct discretization of Maxwell’s Equation )

TLM: Transmission Line Matrix (3-Dimensionaltransmission line matrix representation)

MoM: Method of Moments (requires derivation of Green’s function)

PEM: Parabolic Equation Method (one way axial propagation simulation)PEM: Parabolic Equation Method (one-way axial propagation simulation)

FEM: Finite Element Method (requires discretization in terms of patches)


EM Wave Scattering & Propagation


Lecture 01

Documents

antenna engineering

dipole antenna

slot antennas

loop antennas

antenna measurement

array antenna theory

antennas p i t

s wire antennas