A Reconfigurable Beam Shape Patch Array Antenna (RBS-PA) for WiMAX and WiFi Applications 2 3 4 5 M. JUSOhl, M. Faizal , M. F. Malek , M. R. Kamarudin , M. R. Hamid 12 , School o/Computer and Communication Engineering,
1,2,3
3School o/System Electric Engineering, 4,5 Faculty o/Electrical Engineering, Pauh Putra, Perlis, Malaysia, �Skudai, Johor, Malaysia
'ame
[email protected] '
[email protected] [email protected] '
[email protected] [email protected]
Abstract- A reconfigurable beam shape patch antenna (RBS
shown in section 3. Finally, section 4 concludes the RBS-PA
PA) is proposed in this paper.
research.
The RBS-PA antenna which
consists of two rectangular elements is fed by a 50n microstrip feed line. A feed network technique is implementing to combine
II. ANTENNA DESIGN
both radiating elements. The PIN diode switch is positioned at the transmission line at the ideal location. The activation of certain PIN diode switches configuration would then determine
The proposed RBS-PA antenna is developed from two rectangular elements as shown in Fig. 1. Both elements are
the beam shape angle and main lobe magnitude (dB). The RBS
homogenous which has similar dimension and characteristics
PA is capable of shaped its radiated beam to 9.9dB and 6.7dB.
as well. The basic structure of the single rectangular element
All design and simulations have been carried out using CST
has dimension of 46 mm x 41 mm. The microstrip inset-feed
Microwave Studio. This antenna is a promising candidate to be
line technique has been introduced to each element. The inset
installed for a WiFi and WiMAX smart antenna system.
I.
feed structure performed as tuning circuit to ensure the optimum
INTRODUCTION
Reconfigurable antenna has gain a lot of attentions in wireless
communication
system
impedance
matching
at
frequency
resonant
of
2.37GHz. With few optimization routine, the inset-feed width
recently.
is 0.5 mm for both sides as depicted in Fig. 1.
Reconfigurable
For
array design,
the
inter-element
spacing
(IES)
of
antenna can be classified into three major fields which are
radiating elements must be determined precisely in order to
reconfigurable frequency, polarization and radiation pattern.
get the better antenna performance. In [10], the IES is realized
The reconfigurable antenna can be realized via
RF
switches
to half of Ie in most array cases. Planar array is chosen in this
such as PIN diodes, MEMs and GaAs FETs. By changing the
research as it is more practical and easy to feed each element
switch state to either 'ON' or 'OFF' mode, this determined
by using a feed network. The feed network functioned as
either feed line would receive or not the radio frequency
(RF)
power divider of an array antenna. A quarter wavelength
signal eventually capable for frequency tuning [1 - 4] and as
transformer is use to match the transmission line in order to
impedance matching devices as well [5 - 6].
fix son of input port impedance. This will reflect to more
This research is focuses on the reconfigurable beam shape radiation
pattern
which
suitable
for
point-to-point
power is transmitted to the antenna element rather than reflected back to the source (SMA connector).
communication system that requires high gain characteristics. The integrations of PIN diode switches in the antenna design
Wsub
are potential to deteriorate the gain of the antenna [6 - 9].
Wrad
,------,/
However, the proposed RBS-PA has maximum gain of up to
/
lOdE. Furthermore, the proposed antenna has broad of half power beam-width (HPBW) of 75°.
Ls
All designs and simulations have been carried out using CST Microwave Studio, 3D simulator software. The paper is organized
as
below;
Section
2
discussed
on
antenna
configuration and feed network method as well. Besides, the theoretical simulation technique of representing the PIN diode switches has been elaborated. The result of beam shape radiation pattern with integrations of
978-1-4577-1559-4/12/$26.00 ©2012 IEEE
RF
switches will be
237
0,71Q Input port 50n
Fig. I Simulated geometry of the proposed RBS-PA
The RBS-PA antenna is designed on the 148 mm x 92 mm Taconic (TLY-5) substrate with 2.2 of dielectric, \.5478+/-
- - � ,_
0.02 of thickness, 0.0009 of tangent loss and 35f1m of copper thickness. The proposed antenna has two RF switches outlined
·5
by dotted red rectangles. There are labelled as S1 and S2 which placed at the transmission line feed network.
in
Theoretically, there two methods of developing switching
·10
:s
circuit in simulation software; represent with copper strip line
(f)
and use touch stone block. As in [II], the existence of the
·15
copper strip line indicates ON state condition which input current is allowable to flow. While the absence of copper line
�
means OFF state condition which explain gap exist between two points. The other technique is used a touchstone block (TSB). TSB known as SnP file is an ASCII text file used for
·2 5
1
1 1
-----t----
-'
1 1
1 1
1 1
/
....
----
�
-----
�
-----
1 1 1 1 -----1-----1-----1 1 1 1 " . -----
1 1 -----+---1 1 1 -----r----
�B
Copper strip 1 1 +-__-+ I ___+-__--+___-+-__---i 2.2
2.4
2.6
2.8
3.0
Frequency, GHz
device or passive interconnect network. It has been accepted as a defector standard for the transfer of frequency dependent n-port parameters [12]. Fig. 2(a) and 2(b) illustrated clearly
I'
----�-� ,.,. -...Jf'�----
-----+---.
2.0
documenting the n-port network parameter data of an active
"..
-
Fig. 3 Comparison of TSB and copper strip technique towards the reflection coefficient
the implementation of TSB's diode ON state and diode OFF state in CST Microwave Studio software. The presented RBS-PA antenna is competent to perform
III. RESULT AND DISCUSSION
beam shape ability with sustain frequency operating. This can
Fig. 3 indicates the comparison of TSB and copper strip
be done by certain RF switches configuration as summarized
technique. Both represents switch in ON mode condition. It
in Table 1. There are five parametric analysis to be considered
can be seen that TSB (ON diode) and copper strip have
which are operating band, main lobe magnitude, angular width
similar reflection coefficient and resonant frequency of 2.39 GHz as well. Besides, there is some big ripple between
3dB, radiation efficiency and total efficiency. Fig. 4 illustrates
frequency of 2.6 GHz and 2.8 GHz for copper strip method.
than -10dB. As SI and S2 are ON, the antenna capable to
However, the ripple can be ignored since it does not reach the
function at resonant frequency of 2.39 GHz. This is similar when SI is OFF. While S2 is OFF, frequency resonant shifted to the left with impedance enhancement.
acceptable return loss of less than -lOdB.
2
1 1'
2'
•
the reflection coefficient result under the tolerable Sll of less
Table 1 The PIN diode switches configuration
l;Jz
Number Type of Switch
diode ON staks2p
of PIN diode
PIN diode status
switch
(a)
Reconfigurable
SI
ON
ON
OFF
RF switches
S2
ON
OFF
ON
2.37 -
2.35 -
2.35 -
2.40
2.39
2.39
9.9
6.7
6.7
347.0
346.0
346.0
72.8
75.0
75.0
88.17
83.72
83.72
77.20
83.44
83.44
(R-RFS) Operating Band (GHz) 1
2
l'
2'
I�Z
Main Lobe Magnitude / Gain (dB) Main Lobe Direction (deg.)
diode OFFstate.s2p
Angular width (3dB) / HPBW (deg.)
(b)
Radiation Efficiency
Fig. 2 Schematic diagram of the TSB implementation to the antenna design
238
Total Efficiency
(%)
(%)
' .. · ··· 1 ...
-5
+
.
I
-10
�
:
•
.-
. ..
.....
,
.
I • I -------i----- --,I-------r---I I
_______
____
I I
\� ' I
J,,:
I I I
1 ••••
• •• .- •
. .· ··· · ·--------
------+------+------I
I
-15
: : : -------i-----,r --------r-------i--------
�o
-------�------ }-------�------�--------
(fJ
:
,
I
-25
: :
--------j------
I
:
I
I
: :
:
: :
270
HH-++ -P-k
l-l-+-+-+- H
9(
-- S1, S2 are ON S1 is OFF - - S2 is OFF
-t-------j- ••••
I
I
I
l -------+I ------�------� -30+-------,I--------r 3.0 2.0 2.2 2.4 2.6 2.8 210
Frequency (GHz)
150 180
Fig. 4 Comparison of reflection coefficient by certain PIN diode configuration
Fig. 6 Gain comparison of SI and S2 are ON towards SI is OFF and S2 is ON.
Since
two
radiating
element
of
RBS-PA
antenna
is
IV. CONCLUSIONS
identical, only S 1 is considered. Fig. 5(a) and 5(b) indicate a 3D radiation pattern when (case 1) SI and S2 are ON and (case
In this work, an array antenna with beam shape capability
2) when only SI is OFF at particular frequency of 2.39GHz.
at 2.39 GHz is proposed. A patch antenna is selected due to the
Both have radiation and total efficiency of more than 83% and
easiness to feed each element via feed network. The proposed
77% respectively. Besides, there is significant improvement in
antenna which is square in shape and has a width and length of
terms of gain between case 1 and case 2. This has been clearly
148 x 92 mm can be considered small in size.
compared in Fig. 6 which case 1 has high gain of up to 9.9 dB
antenna has successfully achieved a beam shape ability which
Besides, the
while case 2 only has gain of 6.7dB while the main lobe
is able to radiate with a maximum gain of 6.75 dB and 9.88 dB
direction is approximately similar at 3460•
at
Besides, the half
certain
switch
configuration.
With
all
capability
power beam width (HPBW) of case I is smaller than case 2 at
demonstrated, the presented RBS-PA has a potential to be
72.80 and 75.00 respectively.
implemented in a WiFi and WiMAX smart antenna system.
Freq
9.88dB
Rad. Effic
88.17%
Tot. Effic.
77.20%
•. ss 6.89 4.49 2.1 "
[I]
2.39GHz
Gain
dB
"
�
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