Size Reduction of Microstrip Patch Antennas Using Slotted Complementary Split-Ring Resonators Mohammed M. Bait-Suwailam
Hussain M. AI-Rizzo
Department of Electrical and Computer Engineering,
Department of Systems Engineering,
Sultan Qaboos University,
University of Arkansas at Little Rock
Muscat, Oman
Little Rock, AR,USA
Email:
[email protected]
Email:
[email protected]
Abstract-In this paper, a novel design for miniaturization of microstrip patch antennas is proposed. The technique is based on
resonant tank circuit when both metallic and dielectric losses are neglected.
etching out two Complementary Split-Ring Resonators (CSRRs) from the metallic ground plane beneath two non-radiating edges
Recently, the potential application of CSRRs on minia
of the patch antenna. Numerical simulations are presented for a
turization of patch antennas was explored in [9]-[10]. How
patch antenna with and without the CSRRs. The proposed design
ever, it is important to mention that these attempts relied
is cost effective and useful for miniaturization of patch antennas.
on loading the microstrip patch element with CSRRs, while
Furthermore , unlike other miniaturization techniques that rely
others have achieved miniaturization through etching out the
on either trial-and-error, optimization or randomly orienting the CSRRs beneath the patch antenna , the proposed approach serves as an effective design technique for size reduction of microstrip patch antennas.
CSRRs randomly from the metallic ground plane. However, such techniques would result in increased design complexity and efforts in optimizing optimal locations for CSRRs beneath the radiating patch antenna.
I.
In this work, we demonstrate through numerical simu
INT RODUCTION
lations that by etching two CSRRs from ground plane and
Microstrip patch antennas are very attractive candidates
placing such resonators directly underneath patch antenna's
for use in modern wireless communication systems due to
edges, size reduction of patch antenna is indeed permissible. In
their moderate performance and ease of integration with
[11], a novel slotted CSRR inclusion, known as SCSRR, was
microwave devices. Nowadays, with trends towards down
proposed for mutual coupling reduction between microstrip
scaling of wireless communication devices, compactness of
patch antennas. In this paper, the potential advantage of such
radiating elements becomes extremely important. As such,
complementary resonators in miniaturization of microstrip
miniaturization of microstrip patch antennas is desired without
patch antennas is reported. Numerical studies were carried out
sacrificing performance.
using CST Microwave Studio.
A common methodology that is used to reduce the size
II.
of microstrip patch antennas utilizes dielectric materials with
PROPOSED DESIGN
high-permittivity. However, this deteriorates the far-field per
Fig. 1 shows the numerical setup used to study the filtering
formance of the antenna system due to the existence of surface
capability of SCSRR. A single SCSRR is etched from ground
waves. Several techniques have been reported in the literature
plane underneath a 50-Sl microstrip line, with two lumped
for miniaturization of microstrip patch antennas. Materials with
ports placed at edges of the line, are used to compute the
ceramic substrates were used in [1] to miniaturize microstrip
transmission coefficient. The microstrip line is printed on
patch antennas, which have achieved high miniaturization
a substrate with a relative dielectric constant of 3.48 and
factor at the cost of thick substrates. Microstrip patch antennas
thickness of 1.542 mm. The width of the microstrip line is 3.5
can also be miniaturized by using artificial magneto-dielectric surfaces, high-impedance surfaces (or the so-called
meta
suifaces) [2]-[4]. Recently,
metamaterials have been widely used to synthe
mm. Fig. 2 depicts the transmission coefficient,
S21, computed
for the microstrip line with a single SCSRR inclusion. A stopband behavior below -lOdB can be seen between 4.24.7GHz.
size materials with desirable features for antennas miniatur
Fig. 3 illustrates the geometrical layout of the proposed mi
ization, including double-negative materials and artificial mag
crostrip patch antenna with two slotted-complementary split
netic materials in the form of Split-Ring Resonators (SRRs)
ring resonators. A reference case for patch antenna printed on
[5]. The dual counterpart of SRRs, complementary split-ring
a solid grounded dielectric material is used for comparison
resonators (CSRRs), was first proposed by Falcone et al. [6].
purposes. For simplicity, a square patch antenna with length
Such resonators have been extensively studied, synthesized
L
and applied widely for filters and microwave circuits [7]
5 GHz. The patch antenna is printed on a low-loss dielectric
�
15
illin was considered to resonate at a frequency of ( fr
inclusions etched from ground plane were placed underneath
of an axial electric field. Thus, its equivalent circuit is an LC
two (non-radiating) edges of the patch antenna as shown in
ISBN: 978-1-4673-5613-8©2013 IEEE
=
l.542
illin). Two SCSRR
substrate
magnetic field, a CSRR inclusion resonates upon an excitation
=
3.48 and thickness
h
[8]. Unlike, the SRR unit cell that responds to an axial
528
III.
RESULTS
Fig. 4 depicts the computed reflection coefficient for the patch antenna with and without SCSRRs. Unlike the single resonance of the patch antenna without SCSRRs at 5 GHz, the antenna with SCSRRs has multiple resonant frequencies. The resonance frequency at 4.58 GHz (see Fig. 4) is expected due to the resonance of the SCSRRs when excited with a normal electric field component. Other resonances are attributed to the Fig. 1. Numerical setup to study the stopband hevaior of single SCSRR inclusion that is etched out from ground plane.
strong mutual interaction (i.e., inductive/capacitive coupling) between patch antenna edges and SCSRR inclusions.
-5
-10 CD
:s. (/)N
-15
-20
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Frequency (GHz) Fig. 2. Transmission coefficient for a single SCSRR inclusion underneath the microstrip line.
Fig. 4.
Fig. 3. The size reduction of the patch antenna is achieved here
on patch antenna's resonance, surface current distribution
since the SCSRR inclusions resonate due to the existence of
along patch antenna is shown next. Fig. 5 depicts the current
normal electric field component along the non-radiating edges
distribution along patch antenna when printed on a solid
Reflection coefficient for the patch antenna with and without SCSRRs.
In order to study the effect of slotted-complementary SRRs
of the patch antenna. Furthermore, the two SCSRR inclusions
grounded dielectric slab. Note that the snapshot was recorded
resonate at a lower frequency than the single patch antenna's
at the resonance frequency of 5 GHz. As can be seen from
resonance.
Fig. 5, high concentration of current is observed along patch edges (i.e, slots of the patch) in the reference case (antenna without SCSRRs). However, high concentration of surface current can be seen accumulated along the complementary SRRs, due to the excitation of normal electric field component, in addition to current accumulation along patch edges. The snapshot corresponds to the antenna's resonance frequency of 4.58 GHz when SCSRRs are etched from ground plane. Fig. 7 depicts the surface current distribution along the antenna with SCSRRs corresponds to the resonance frequency of 5.32GHz.
SCSRRs
This case is different from the surface current distribution shown in Fig. 6 in that high current is concentrated between
Ground plane
Patch antelma
�
the edges of the patch and SCSRRs. Furthermore, less current is observed throughout the patch antenna surface. This is attributed to a strong capacitive coupling between the antenna's edges and SCSRR inclusions. The far-field patterns of the microstrip patch antenna are
Fig. 3. View of a square microstrip patch antenna with the resonators etched from ground plane beneath the antenna. The white dashed lines represent the etched SCSRRs from ground plane. Note that the geometry is not drawn to scale.
shown next for both ground plane with and without SCSRRs in Figs. 8- 9. The gain pattern for the solid ground case was computed at the resonance frequency of the antenna (5 GHz), while the pattern for the loaded ground plane was taken at the resonance frequency of 4.58 GHz. Similar radiation
ISBN: 978-1-4673-5613-8©2013 IEEE
529
antenna with and without SCSRRs show same performance at the resonant frequencies, which was around 88%. solid ground - - - ground with resonators
--
o 10
30
5 0 -5 -10 -15
270
-10 -5 Fig. 5. Top view of surface current distribution along patch antenna without SCSRRs captured at antenna's resonance frequency 5GHz.
0 5 10
210
150 180
Fig. 8. E-plane gain patterns for the patch antenna with and without SCSRRs.
--
o
solid ground
- - - ground with resonators 30
Fig. 6. Top view of surface current distribution along patch antenna with SCSRRs captured at 4.58GHz.
150 180
Fig. 9. H-plane gain patterns for the patch antenna with and without SCSRRs.
IV.
CONCLUSION
In conclusion, a technique for size reduction of microstrip patch antennas is presented. The proposed methodology em ploys two slotted CSRRs that are etched out from ground Fig. 7. Top view of surface current distribution along patch antenna with SCSRRs captured at 5.32GHz.
plane, and placed directly underneath the antenna's non radiating edges. The technique is simple and easy to fabricate using traditional milling techniques. It was found that a size reduction of almost 10% is achieved for microstrip patch
performance at broadside is observed between the two cases,
antenna when SCSRRs are etched in ground plane.
except minimal radiation can be seen due to the perforations in
The far-field patterns of the patch antenna with the res
the ground plane. Fig. 9 shows the H-plane gain patterns for the
onators show similar performance to the patch antenna on a
aforementioned two cases. Again, similar radiation is observed
solid ground plane, despite a small back lobe that was observed
between the two cases. The radiation efficiency of the patch
due to the perforations in the ground plane.
ISBN: 978-1-4673-5613-8©2013 IEEE
530
REFERENCES [1]
J. Kula, D. Psychoudakis, w.-J. Liao, C.-c. Chen, J. Volakis, and J. Halloran, "Patch-antenna miniaturization using recently available ceramic substrates," IEEE Antennas Propag. Mag., vol. 48, no. 6, pp. 13-20, Dec. 2006.
[2]
D. Sievenpiper, L. Zhang, R. Broas, N. Alexopolous, and E. Yablonovitch, "High-impedance electromagnetic surfaces with a forbidden frequency band," IEEE Trans. Microw. T heory Tech., vol. 47, no. 11, pp. 2059-2074, Nov. 1999.
[3]
H. Mosallaei and K. Sarabandi, "Antenna miniaturization and band width enhancement using a reactive impedance substrate," IEEE Trans. Antennas Propag., vol. 52, no. 9, pp. 2403-2414, Sept. 2004.
[4]
P. !konen, S. Maslovski, C. Simovski, and S. Tretyakov, "On artificial magnetodielectric loading for improving the impedance bandwidth properties of microstrip antennas," IEEE Trans. Antennas Propag., vol. 54, no. 6, pp. 1654-1662, June 2006.
[5]
G. Singh, "Double negative left-handed metamaterials for miniatur ization of rectangular microstrip antenna," Journal of Electromagnetic Analysis and Applications, vol. 2, no. 6, pp. 347-351, 2010.
[6]
F. Falcone, T. Lopetegi, 1. Baena, R. Marques, F. Martin, and M. Sorolla, "Effective negative- E stopband microstrip lines based on comple mentary split ring resonators," IEEE Microwave Wireless Compo Lett., vol. 14, no. 6, pp. 280-282, Jun. 2004.
[7]
J. Garcia-Garcia, F. Martin, F. Falcone, J. Bonache, J. Baena, I. Gil, E. Amat, T. Lopetegi, M. Laso, J. Iturmendi, M. Sorolla, and R. Mar ques, "Microwave filters with improved stopband based on sub wavelength resonators," IEEE Trans. Microw. T heory Tech., vol. 53, no. 6, pp. 1997-2006, June 2005.
[8]
J. Bonache, I. Gi\, J. Garcia-Garcia, and F. Martin, "Novel microstrip bandpass filters based on complementary split-ring resonators;' IEEE Trans. Microw. T heory Tech., vol. 54, no. 1, pp. 265-271, Jan. 2006.
[9]
R. Ouedraogo, E. Rothwell, A. Diaz, K. Fuchi, and A. Temme, "Minia turization of patch antennas using a metamaterial-inspired technique," IEEE Trans. Antennas Propag., vol. 60, no. 5, pp. 2175-2182, May 2012.
[l0]
Y. Dong, H. Toyao, and T. Itoh, "Design and characterization of miniaturized patch antennas loaded with complementary split-ring res onators," IEEE Trans. Antennas Propag., vol. 60, no. 2, pp. 772-785, Feb. 2012.
[11]
M. Bait-Suwailam, O. Siddiqui, and o. Ramahi, "Mutual Cou pling Reduction Between Microstrip Patch Antennas using Slotted Complementary Split-Ring Resonators," IEEE Antenna Wireless Prop agat. Lett., vol. 9, pp. 876-878, 2010.
ISBN: 978-1-4673-5613-8©2013 IEEE
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