Dr. Stuart Long - University of Houstoncourses.egr.uh.edu/ECE/ECE5318/ANTENG...
Transcript of Dr. Stuart Long - University of Houstoncourses.egr.uh.edu/ECE/ECE5318/ANTENG...
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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