ANTENNA THEORY by Constantine A. Balanis Chapter 2.2.5 – 2
Transcript of ANTENNA THEORY by Constantine A. Balanis Chapter 2.2.5 – 2
Hanyang University
1/29 Antennas & RF Devices Lab.
WEEKLY SEMINAR
Sunryul Kim2019.01.23
Hanyang University
2/29 Antennas & RF Devices Lab.
Paper Review I Paper Review II
Single-Layer Circularly Polarized Antenna With Fan-Beam Endfire Radiation
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 16, 2017
FREQUENCY
5.8 GHz Band
STUCTURE
M-dipole
Double-side slot-coupled line
(DSSCL)
Double-side parallel strip line
(DSPSL)
E-dipole
COMPARISON
Bandwidth / Beamwidth /
Dimensions
SUMMARY
Fig.1 Antenna geometry
FIGURES
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3/29 Antennas & RF Devices Lab.
SUBSTRATE
F4B material (εr = 2.65, tanδ = 0.0013)
PARAMETERS
Fig.2 Antenna configuration :
(a) geometry ; (b) exploded perspective view.
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CONFIGURATION
(b)
(a)
FIGURE
d = 1 mm s = 1.5 mm w =31 mm
l = 16.58 mm h = 1.5 mm lm = 7.78 mm
we = 1.5 mm le = 21.64 mm lec = 5.2 mm
lp = 1.35 mm gp = 0.2 mm wp =0.2 mm
dd = 0.4 mm ld = 7.96 mm wd = 0.8 mm
gd = 0.6 mm d0 = 0.6 mm df = 2.7 mm
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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4/29 Antennas & RF Devices Lab.
TWO IDENTICAL CONDUCTORS
VIA HOLES
By terminating one of its transverse
edges with via holes, a substrate
integrated shorted parallel-plate cavity
is formed
Its open aperture plays the role of
equivalent magnetic dipole
Fig.3 Part 1 : Magnetic dipole
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EXPLANATIONM-DIPOLE
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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Since the electric field near the edge of the
cavity is sufficiently large while the
electric current is quite small, this
structure can efficiently realize the energy
coupling without generating obvious
spurious radiation.
Fig.4 Part 2 : T-shaped double-side slot-coupled line
(DSSCL)
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DSSCL EXPLANATION
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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6/29 Antennas & RF Devices Lab.
A meandered double-side parallel strip
line (DSPSL) with chamfered cutting
edges is directly connected to the
outstretched end of the DSSCL
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Fig.5 Part 3 : Meandered double-side parallel strip line
(DSPSL)
DSPSL EXPLANATION
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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Two conductor arms are printed along the
opposite directions with a total length of le,
while lec marks their overlapped length.
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Fig.6 Part 4 : Electric dipole
E-DIPOLE EXPLANATION
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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8/29 Antennas & RF Devices Lab.
At a point along the endfire direction, the
electric field can be expressed as
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Fig.7 Equivalent model from the view of field
synthesis
FIGURE EXPLANATION
If the design goal is realize LHCP at the
exactly endfire direction,k = 1
β = 270˚
E=θ Eθ+φ k ∙ Eθ ∙ e jβ
k = |Eφ| / |Eθ|
β =∠Eφ−∠Eθ
According to the definition of axial retio
(AR)
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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9/29 Antennas & RF Devices Lab.
Relative magnitude and phase delay of
power flowing from the magnetic dipole to
the electric dipole are marked as
parameters m and α
And they are respectively relevant to
parameters k and β
M-dipole has omnidirectional radiation,
while E-dipole radiate at the positive half-
space beside xz-plane for the existence of
backward conductors, the value of k is
about twice of m
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CLIPBOARD EXPLANATION
E=θ Eθ+φ k ∙ Eθ ∙ e jβ
k = |Eφ| / |Eθ|
β =∠Eφ−∠Eθ
Fig.7 Equivalent model from the view of field
synthesis
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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10/29 Antennas & RF Devices Lab.
Overall phase difference at the observation point comes
from two aspects
The feeding phase difference caused by the traveling
of electromagnetic wave from the shorted parallel-
plate cavity to the printed arms
The spatial phase difference caused by the
noncoincidence of the positions of two
complementary dipoles along the direction of wave
propagation
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PHASE
M-dipole has omnidirectional
radiation, while E-dipole
radiate at the positive half-
space beside xz-plane for the
existence of backward
conductors, the value of k is
about twice of m
MAGNITUDE
k ≈ 2 × m Required feeding phase delay for generating ideal CP
wave
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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11/29 Antennas & RF Devices Lab.
The widths and lengths of DSSCL, DSPSL, and the electric dipole all have influences on the
relative power and phase delay between the load and the source.
To simplify the design procedure, only θp and θd are chosen as the variables to realize the
tuning of m and α here.
Shortening the distance between two dipoles is beneficial for achieving a wider AR beamwidth
and higher gain
DSPSL of a narrow linewidth is adopted, which makes its characteristic impedance higher
than the input impedance of a normal half-wavelength E-dipole.
By increasing the length of the E-dipole, real and imaginary parts of its input impedance rise,
which makes it inductive.
Two printed arms are designed with an overlapped, which can be modeled as a capacitor.
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Fig.8 Equivalent model from the view of microwave matching circuit
PROCEDURE
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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12/29 Antennas & RF Devices Lab.
The width of DSPSL is chosen to be
0.8mm, which correspond to a
characteristic impedance of
approximately 170.1 Ω
le = 21.64 mm and lec = 5.2 mm
Thanks to stable directivity of the dipole
antenna over a sufficient large length
variation, the final radiation pattern is
almost unaffected after the modification
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IMPEDANCE EXPLANATION
Fig.9 Effects of lengths le and lec on the input
impedance of the electric dipole at 5.8 GHz.
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
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PARAMETERSVERIFICATION
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Impedance of Port 2 is defined as
169.7889 + j 0.1793 Ω
m can be effectively controlled by lp
m is almost independent of ld
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MAGNITUDE EXPLANATION
Fig.10 Effects of lengths ld and lp on relative
magnitude between two dipoles.
Port 1 : power feed
Port 2 : electric dipole
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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14/29 Antennas & RF Devices Lab.
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PHASE EXPLANATION
Fig.11 Effects of lengths ld and lp on relative phase
delay between two dipoles.
Impedance of Port 2 is defined as
169.7889 + j 0.1793 Ω
α can be effectively controlled by either lp
or ld
Final design point marked by the
pentagram shows | S21 | = − 4.4 dB , which
corresponds to m = 0.56
α = 312.1°, which is also close to the
required 308.6° Port 1 : power feed
Port 2 : electric dipole
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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15/29 Antennas & RF Devices Lab.
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PROTOTYPE
Fig.12 Photogtaph of the planar endfire CP anternna
prototype.
Using a standard PCB fabrication process
Agilent’s N5230A vector network analyzer
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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16/29 Antennas & RF Devices Lab.
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VERSUS FREQUENCY
Fig.13 (a) S11 and efficiency versus frequency and (b)
AR and gain versus frequency
Both simulated and measured results are
in good agreement
Measured −10 dB bandwidth is from 5.7
to 5.9 GHz (3.5%)
Radiation efficiency at the desired band is
more than 90%
Measured 3 dB AR bandwidth is found to
be 5.65 – 5.9 GHz (4.3%)
The discrepancies are mainly attributed to
the fabrication tolerance and test
environment
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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17/29 Antennas & RF Devices Lab.
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RADIATION PATTERN
Fig.14 Radiation patterns at 5.8 GHz: (a) azimuth
plane and (b) elevation plane.
The measured gain at the exactly endfire
direction is 3.99 dBi
Wide coverage is obtained as can be
clearly seen
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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18/29 Antennas & RF Devices Lab.
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PERFORMANCE COMPARISONS
CONFIGURATIONDESIGN
FIELD
DESIGN
MATCHING
DETERMINE
PARAMETERSVERIFICATION
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19/29 Antennas & RF Devices Lab.
Paper Review I Paper Review II
Wearable Dual-Band Magneto-Electric Dipole Antenna for WBAN/WLAN Applications
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 63, NO. 9, SEPTEMBER 2015
APPLICATION
WBAN/WLAN
FREQUENCY
2.45 GHz Band
5 GHz Band
STUCTURE
Magneto-Electric Dipole
ANALYSIS
S11 / Radiation Pattern / Gain /
Efficiency / Bending / SAR
SUMMARY
Fig.15 Antenna geometry
FIGURES
Fig.16 Bending insensitive
antenna
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SUBSTRATE
3-mm-thick Felt textile
(εr = 1.3, tanδ = 0.044)
CONDUCTOR
0.17-mm-thick ShieldIt Super conductive
textile (conductivity = 1.18 × 105 S/m)
Based on the conventional magneto-
electric dipole topology, which combines a
planar magnetic dipole with an electric
dipole.
Two U-shaped slots are cut in the planar
electric dipole.
Fig.18 Felt textile, ShieldIt Super
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GEOMETRY FIGURE
Fig.17 Antenna geometry.
Physical dimensions in mm.
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
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21/29 Antennas & RF Devices Lab.
Wideband
Low back radiation
By positioning an electric and a magnetic
dipole orthogonally with respect to each
other, the antenna forward radiation can
be enhanced while simultaneously
reducing the back radiation.Fig.19 Operating theory of magneto-electric dipole
antenna.
Paper Review I Paper Review II
THEORYFIGURE
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
Hanyang University
22/29 Antennas & RF Devices Lab.
Without slots 2.45 GHz : Two resonances can be combined
to form a wide band
5 GHz : The electric and magnetic
resonances are sill separated
Bringing the two resonances closer
together by the addition of the slots Two resonances are combined to form a very
wide upper band from 4.57 to 6.28 GHz
This however results in a bandwidth
degradation in the first band – from 670
MHz for the antenna without slots to 490
MHz for the slotted antenna
Nonetheless this 490 MHz band width is sill
more than sufficient to meet the
WBAN/WLAN requirements
Fig.20 Simulated and measured reflection coefficients.
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SIMULATIONS-PARAMETER
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
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23/29 Antennas & RF Devices Lab.
Lower band Two measured resonances are slightly more
separated from each other compared to the
simulations
This result in a maximum S11 of -7.5 dB
within the required band, which is still
acceptable in many real applications
Theses slight disagreements are mainly
caused by the fabrication inaccuracies
and the inhomogeneous material
properties
Upper band The same tendency is observed, but less
severe
S11 never goes above -10 dB
The measured bandwidth is wider than the
simulated one
Fig.20 Simulated and measured reflection coefficients.
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MEASURES-PARAMETER
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
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24/29 Antennas & RF Devices Lab.
Stable radiation characteristic is
observed throughout the
operating frequency band
Broadside pattern with high
front-to-back ratio (FBR)
The higher cross polarization in
the upper band is caused mainly
by the feeding pin, which has a
considerable length compared to
the wavelength
Fig.21 Simulated and measured radiation patterns : in the xz plane at (a) 2.3
GHz ; (b) 2.6 GHz ; (c) 5.2 GHz ; (d) 5.8 GHz ; in the yz plane at (e) 2.3
GHz ; (f) 2.6 GHz ; (g) 5.2 GHz ; and (h) 5.8 GHz.
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Red : simulated copolar
Magenta : measured copolar
Black : simulated cross-polar
Blue : measured cross-polar
RADIATION PATTERN
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
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25/29 Antennas & RF Devices Lab.
The measured forward realized gain is at
least 4.7 and 3 dB in the lower and upper
frequency band, respectively
The radiation efficiency and the total
efficiency are both above 50% and 60% in
the lower and upper band, respectively
Fig.22 Simulated efficiency and gain of the antenna.
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MEASUREEFFICIENCY & GAIN
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
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26/29 Antennas & RF Devices Lab.
The antenna mounted on a vacuum
cylinder with a varying radius r.
When bending radius is reduced
Lower band increases
Upper band narrows
But the changes are insignificant
Directivity & Gain are lower
Since the bending decreases the
electrical size of the ground, especially
in the lower band
Nevertheless, these value are still
acceptable for on-body communication.
From this evaluation, it is clear that
once an accurate fabrication can be
established, the antenna is observed to
be very robust against bending.
Fig.24 Simulated S11 under bending conditions.
Bending along a cylinder.
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CYLINDERBENDING CONDITIONS
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
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27/29 Antennas & RF Devices Lab.
This mimics the normal wrinkling of cloth
on the human body
As the wrinkling becomes denser, the
bandwidth of the antenna decreases in
both bands
However, even wrinkling angle is the most
extreme, i.e. 60˚, the bandwidth are
maintained at 115 and 655 MHz in the
lower and upper band, respectively.
Also, no significant degradations occur in
terms of gain and FBR
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NOTCHED CURVEBENDING CONDITIONS
Fig.25 Simulated S11 under bending conditions.
Bending along a notched curve, p = 10 mm.
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
Hanyang University
28/29 Antennas & RF Devices Lab.
Human tissue model
3-mm-thick skin layer
7-mm-thick fat layer
60-mm-thick muscle layer
300 mm × 300 mm sized
6 mm from the antenna ground
The SAR value is calculated based on the
IEEE C95.1 standard and averaged over
10 g of biological tissue
It is clear that the estimated maximum
SAR value is 0.045, which is far below the
European threshold of 2 W/kg
Paper Review I Paper Review II
SAR
Fig.26 SAR distributions at different frequencies. (a)
2.45 GHz. (b) 5.2 GHz. (c) 5.8 GHz.
GEOMETRY THEORYRETURN
LOSS
RADIATION
PATTERNEFFIC.&GAIN BENDING SAR
Hanyang University
29/29 Antennas & RF Devices Lab.
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