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APPENDIXAPPENDIXA Little Bit ofA Little Bit ofMany ThingsMany Things

ECE 5318/6352ECE 5318/6352Antenna EngineeringAntenna Engineering

Dr. Stuart LongDr. Stuart Long

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LOOP ANTENNASLOOP ANTENNAS(Ch. 5)(Ch. 5)

Small constant current loops

UHF-TV

λ<<r

Loops comparable to a wavelength

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LOOP ANTENNASLOOP ANTENNAS

( ) ( ) ''' ,,4

dlR

ezyxzy,x,jkR

'−

∫=c

IAπμ

λ1.0=C

λ5=C

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LOOP ANTENNASLOOP ANTENNAS

Ferrite-loaded multi-turn loops

(AM radio)

To increase antenna efficiency

Increase circumference of loop or

Insert a ferrite core within the circumference

Multi-turn loop

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LOOP ANTENNASLOOP ANTENNAS

C1

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ARRAYSARRAYS(Chs. 6 (Chs. 6 –– 7 7 -- 8)8)

Retro directive (Van Atta)

Adaptive ArraysSignal processingComplex weightingNull adjusting

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ARRAYSARRAYS

Distributions: Taylor, triangular, Continuous distributionsSuperdirectivity

2coscos,

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ARRAYSARRAYS

Planar arrays

Circular arrays

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ARRAYSARRAYS

Dipole Self impedance

⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ −== '

max 2sin2 zlkIJaI zz π

( ) ( ) ''2/

2/

'2max

,,1 dzzzaEzzaII

Z zzm ====−= ∫−

ρρ

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ARRAYSARRAYS

Dipole Mutual impedance

Configuration of two identical elements Configuration of two identical elements for mutual impedance computationsfor mutual impedance computations

Side by sideSide by sideCollinearCollinear Parallel in echelonParallel in echelon

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ARRAYSARRAYS

Dipole Mutual impedance

( ) ='21 zEz

( ) ( ) ''21

2/

2/

'2

221

1 dzzEzII

V zi∫

−

−=

( ) ( ) ''21

2/

2/

'2

211

2121

1 dzzEzIIII

VZ ziii∫

−

−==

Induced open-circuit voltage in antenna 2, referred to its current at the input terminals,

due to radiation from antenna 1

E-field radiated by antenna 1

( ) ='2 zI Current distribution along antenna 2

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Numerical MethodsNumerical Methods(Ch. 8)(Ch. 8)

Method of Moments (MININEC)

Finite element method (HFSS)

Geometric Theory of Diffraction (GTD)

Integral Equation Techniques

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MATCHING MATCHING TECHNIQUES TECHNIQUES

(Ch. 9)(Ch. 9)

WHY MATCHING IS NEEDED?

Antenna operation depends on the frequency characteristics of the transmission line-antenna combination.

Transmission line impedance is usually real whilethat of the antenna is complex.

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MATCHING MATCHING TECHNIQUES TECHNIQUES

Cylindrical dipole

-finite radius of linear antenna

Folded dipole

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MATCHING TECHNIQUES MATCHING TECHNIQUES

QUARTER-WAVELENGHT TRANSFORMER

STUB-MATCHING

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MATCHING TECHNIQUES MATCHING TECHNIQUES

OMEGA MATCH

GAMMA MATCH

T-MATCH

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MATCHING TECHNIQUES MATCHING TECHNIQUES

Balun

Bal Un

Balancedcurrents

Unbalancedcurrents

balanced line

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MATCHING TECHNIQUES MATCHING TECHNIQUES

BALUNS AND TRANSFORMERS

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TRAVELING WAVE ANTENNASTRAVELING WAVE ANTENNAS(Ch. 10)(Ch. 10)

Long wireRhombic antenna

V-antennaBeverage antenna

Antennas whose current and voltagedistributions can be represented by one or

more traveling waves

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TRAVELING WAVE ANTENNASTRAVELING WAVE ANTENNAS

Helical antenna

Leaky wave antennaPeriodic structure

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APERTURE ANTENNASAPERTURE ANTENNAS(Ch. 12)(Ch. 12)

rectangular and circular

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APERTURE ANTENNASAPERTURE ANTENNAS

Babinet’s Principle

In optics, it states that when the field behind a screen with an opening is added to the field of a complementary structure, the sum is equal to the field when there is no screen.

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APERTURE ANTENNASAPERTURE ANTENNAS

slots

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APERTURE ANTENNASAPERTURE ANTENNAS

W/G

aperture feeds

cavity backed

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LENS ANTENNALENS ANTENNA

microwave version of optical lens

air-feed for arrays

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RADOMESRADOMES

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

excite by probe or aperture couplingexcite by probe or aperture couplinglow loss, broad bandwidthlow loss, broad bandwidthhigh frequency applicationshigh frequency applications

rε

ground plane

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

DRA GEOMETRIES

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNASFEEDING STRUCTURES

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

z

a l

r12

ε

θ

r

bx

Ground plane

Coaxial probe

x

y

z

φ

Hemispherical DRA Coaxial probe

Ground plane

FEEDING STRUCTURES

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

FEEDING STRUCTURES

strip−μ probe

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

FEEDING STRUCTURES

stripconformal

slot

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

RADIATION PATTERN

Measured and calculated fields various a/d ratios: a/d=0.5

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

INPUT IMPEDANCE

Input impedance of the TE111 mode versus frequency:a=2.54 mm, l=1.52 mm, εr=8.9, r1=0.075 mm.

Input impedance of the TE111 mode versus frequency for different probe lengths:

a=2.54 mm, b=1.74 mm, εr=8.9, r1=0.075 mm.

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

INPUT IMPEDANCE

Input impedance of the TM101 mode versus frequency:A=11.5 mm, l=4.5 mm, εr=9.8, r1=0.075 mm.

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

COMPOSITE GEOMETRIES

1rε

3rε

2rε

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DIELECTRIC RESONATOR ANTENNASDIELECTRIC RESONATOR ANTENNAS

CONFORMAL DRA

rε