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A Higher-Mode Annular-Ring
Patch Antenna With a
Photonic-Bandgap Ground Plane
Shun-Yun Lin
Department of Electrical Engineering
Cheng Shiu Institute of Technology
Kaohsiung, Taiwan
Email: [email protected]
Kin-Lu Wong
Department of Electrical Engineering
National Sun Yat-Sen University
Kaohsiung, Taiwan
Email: [email protected]
OUTLINE
 INTRODUCTION

Annular-ring patch antenna operated at TM21 mode

Patch antenna with a PBG ground plane
 ANTENNA DESIGNS
 EXPERIMENTAL RESULTS
 CONCLUSIONS
INTRODUCTION-1
Mode Chart for microstrip ring resonanto
r
3.5
3
2.5
2
1.5
1
0.5
5
0.9
5
0.8
5
0.7
5
0.6
5
0.5
5
0.4
5
0.3
5
0.2
5
TM11
0.1
5
0
0.0
normalized propa. const. kR
The resonant frequency
of TMnm mode can be
calculated by the mode chart
As w/R is increased, the value
of kR becomes less than n for
a given mode
When the ring width reach
half the guided wavelength,
higher order TMnm(n0, m>1)
appear.
normalized ring width- w/R
TM21
TM31
R
2w
INTRODUCTION-2
The typical radiation has a peak value at about 35° away
from broadside direction
Both horizontal and vertical planes have conical radiation
patterns
The radiated power in azimuth plane is non-uniform
INTRODUCTION-3
Patch antenna with slotted ground plane


r
r



Compact LP antenna
Compact DP antenna


Compact CP antenna
INTRODUCTION-4
Patch antenna with Photonic BandGap ground plane

PBG structure is a periodic structure

The forbidden bands are characterized by




period of structure
shape of the individual element of the lattice
size of the individual element of the lattice
Applied to antenna design




isolation enhancement
harmonic control
gain enhancement
impedance bandwidth enhancement
ANTENNA DESIGN-1
PBG ground plane
A square lattice of 3 x 3
circular slots are embedded
The ratio of the slot radius
to the PBG period is selected to be
0.25 to obtain optimum stopband
depth and passband ripples
The center frequency f0 of the
stopband is determined from
f0 = c/2S
ANTENNA DESIGN-2
Slotted ground plane
Four circular slots are
embedded in ground plane
– have the same radius and
spacing as those embedded
in the PBG ground plane
– placed in perpendicular
to the surface current path
of TM21 mode
– located almost under the
annular-ring radiating patch
EXPERIMENTAL
RESULTS-1
Antenna with regular
ground plane
Antenna with slotted
ground plane
Antenna with PBG
ground plane
EXPERIMENTAL
RESULTS-2

The resonant frequency of the
antenna with a slotted ground
plane was greatly lowered

The resonant frequency of the
antenna with a PBG ground
plane was slightly increased

The impedance bandwidth for
both antennas with the slotted
and PBG ground planes are
larger than the reference
antenna
EXPERIMENTAL
RESULTS-3


Good conical radiation
patterns are observed for
three studied antenna,
especially for the antenna
with PBG ground plane
The radiation patterns of
the antenna with slotted
ground plane has smaller
beamwidth
(a) Ref. Antenna at 2380 MHz
(b) Antenna with slotted GND at 1920 MHz
(c) Antenna with PBG GND at 2460 MHz
EXPERIMENTAL
RESULTS-4
The studied antenna with slotted ground plane
has a patch size reduction of about 35%
The studied antenna with PBG ground plane has
a large F/B ratio of 12.1 dB
EXPERIMENTAL
RESULTS-5
The antenna with a slotted ground
plane has the largest peak antenna
gain
The gain variations of the antenna
with a PBG ground plane is less
than 0.5 dBi
Ref.
antenna
Antenna with
slotted GND
Antenna with
PBG GND
CONCLUSIONS
 Annular-ring patch antenna with a slotted ground plane
Patch size reduced
Impedance bandwidth enhanced
Backward radiation increased
 Annular-ring patch antenna with a PBG ground plane
Impedance bandwidth enhanced
F/B ratio enhanced
Small gain variations within the impedance bandwidth