1. International INTERNATIONAL JOURNALEngineering & Technology (IJECET), ISSN 0976
Journal of Electronics and Communication OF ELECTRONICS AND
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
– 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEME
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 3, Issue 3, October- December (2012), pp. 197-201
IJECET
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ANTENNA MINIATURIZATION TECHNIQUES FOR WIRELESS
APPLICATIONS
Rajendra R. Patil1, Vani R. M2, 3P.V. Hunagund
1
Dept. of E&CE, Appa Institute of Engineering & Technology, Gulbarga-585103,
Karnataka, India. Email- rajurpatil@yahoo.com
2
University Science Instrumentation Centre, Gulbarga University, Gulbarga-585106 Karnataka,
India. Email-vanirm12@rediffmail.com
3
Dept. of Applied Electronics, Gulbarga University, Gulbarga-585106, Karnataka, India
Email-pvhunagund@gmail.com
ABSTRACT
This paper reports simulated analysis of small planar antennas (Microstrip Patch Antennas)
miniaturization using different methodologies. The effect of miniaturization on antenna
parameters like resonance frequency, return loss, radiation efficiency, and bandwidth are
discussed.
Keywords: antenna miniaturization, microstrip patch antenna, magneto-dielectrics
1. INTRODUCTION
Antenna is a device designed for radiating or receiving radio waves [1]. The microstrip
antennas also referred to as microstrip patch antennas (MSA) have several advantages like
small size, light weight, low cost, low volume and easy to fabricate using printed circuit
technology over conventional microwave antennas and therefore are widely used in many
practical applications like aircraft, spacecraft, satellite, missile, mobile, GPS, RFID, Wi-Max
and Radar etc. The radiating elements and the feed lines are usually photo etched on the
dielectric substrate. MSAs suffer from disadvantages like low radiation efficiency, low gain,
high Q, narrow impedance bandwidth etc.
Wireless systems and their size reduction (miniaturization) has become a vital issue now a day.
The demand for commercial and military mobile wireless communication system is on the rise.
Smaller physical size, higher radiation efficiency, and wider bandwidth are three desired
characteristics of antennas for communication systems. Some approaches for antenna
miniaturization are introduction of slots, slits, short meandering and novel geometries like
fractals or by using higher dielectrics constant. However, all the above techniques results in
reactive loading of the antenna and hence results in higher Q and reduced bandwidth, making
them unsuitable for most of the applications [2-3]. To achieve wide bandwidth it is a general
method using of thick dielectric substrate. However, it decreases the antenna gain by increasing
storing of energy within substrate. Recently, magneto-dielectric substrate with permittivity and
permeability higher than one has been proposed [4]. This approach uses nanotechnology tools
and techniques for the development of magneto-dielectric substrates [5] [6]. This paper
presents simulation analysis of antenna miniaturization using (a) slots in the patch of the
antenna (uses simple fabrication), (b) loading high value permittivity in the substrate of the
antenna, and (c) loading magneto-dielectrics in the substrate of the antenna (permittivity,
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEME
October
permeability values greater than one are known with negligible material loss). Magneto-
dielectrics property in the material can be developed by nano composite materials like Nickel-
Nickel
Cobalt-Zink Ferrites, Copper-Cobalt
Cobalt-Zink Ferrites, Cobalt-silica-BCB etc., as substrate
BCB
material [5-7]. These types of material development make use of nanotechnology.
2. BASE ANTENNA DESIGN AND SIMULATION
For antenna miniaturization, aperture coupled microstrip patch antenna (ACMSA) is preferred
and selected as it offers greater design flexibility. The base antenna ACMSA is designed and
desig
simulated at 2.2GHz for FR4 substrate with a thickness of 1.6 mm and dielectric constant of
4
2.54, illustrated in fig.1 (a) and 1(b) [7]. In ACMSA, the field is coupled from the microstrip
(b) ].
line feed to the radiating patch through an electrically small aperture or slot cut in the gro
ground
plane. The coupling aperture is usually centered under the patch, providing low cross- cross
polarization due to the symmetry. The shape, size, and location of the aperture decide the
amount of coupling from the fed line to the patch. The antenna design was undertaken through
undertaken
simulations using the IE3D software version 14.65. IE3D is a full wave EM solver [8]. It
full-wave
solves the Maxwell Equations, which govern the macro electromagnetic phenomenon. There is
no much assumption involved except the numerical nature of the method. Therefore, the
Theref
solution is extremely accurate. The simulated result for base antenna is listed in Table 1.
(a) (b) (c) (d) (e)
Figure 1. (a) ACMSA geometry (b) simulated geometry (c) electric current distribution (d)
magnetic current distribution (e) both electric and magnetic current distribution.
3. ANTENNA MINIATURIZATION BY USE OF SLOTS IN THE PATCH
Fig. 2(a) shows the antenna structure with a rectangular patch and two rectangular slots on
)
either side in it. The shape of this antenna is similar of the one in fig.1 (a). However with
.
changing the dimensions in the patch, the effect of slots on the properties of the antenna have
been changed and listed in Table 1. It can be seen that by introducing two slots on either side of
1. e
the patch there is a lower frequency shift and hence miniaturization of 11.56 percent. However
percent
there is a decrease in return loss, bandwidth and radiation efficiency The simulated result is
efficiency.
listed in table 1.
µr = 1, εr = 2.54
(a) (b)
(b (c) (d)
Figure 2. (a) ACMSA simulated geometry with slots (b) electric current distribution (c)
magnetic current distribution (d) both electric and magnetic current distribution.
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October December (2012), © IAEME
October-
Figure 2(a) shows simulated ACMSA geometry with two slots of size 3mm x 24mm on either
side in the conducting patch, and current distributions. Across slot we have magnetic current
which couples feed line and centre of the patch at which electric field is zero. However there is
Howev
a maximum current distribution on either side of the patch. Also we can notice increase in path
of vector current compared with current distribution in base antenna. The presence of slots
increases current path length which gives lower shift in resonant frequency and decrease in
efficiency and bandwidth.
4. ANTENNA MINIATURIZATION BY USE OF HIGH PERMITTIVITY
DIELECTRIC MATERIALS
The uses of high permittivity substrate allow reducing the electrical size of the antenna through
the reduction of the effective wavelength ( λ ), and bandwidth related to permittivity ( ε ) and
he ,
permeability ( µ ) are given by the equations
λ=λ o / ε r µ r ; BW ≈ µ / ε (1)
where λ o is free space wavelength. As it can be seen in the denominator, with µ r =1 , the antenna
miniaturization is achieved by controlling
controlling/varying only ε r . For different values of ε r (for
example: 3, 4, 5), the antenna is simulated for miniaturization. The simulated parameters are
he
listed in Table 1. From the table it is clear that the use of high permittivity dielectric materials
.
offer an interesting size reduction (by slowing the confined wave inside the substrate), but the
subs
bandwidth and radiation efficiency is significantly reduced due to field confinement around the
high permittivity region. Fig. 3(b)- illustrates simulated results.
-(d)
From the equations of the electrical wavelength and bandwidth, high permittivity or high
permittivity
permeability materials are good at reduction of size but these causes decreasing of bandwidth
bandwidt
or increasing of loss tangent respectively. Therefore, the use of high permittivity dielectric
material is often restricted to antennas operating at a single narrow band application like GPS
and Bluetooth.
µ=1, εr >2.54
r
(a) (b) (c) (d)
Figure 3. (a) ACMSA with high dielectrics (b) Return loss Vs Frequency (c) 2D Radiation
.
pattern (d) Efficiency Vs frequency
4. ANTENNA MINIATURIZATION BY USE OF MAGNETO-DIELECTRICS
ZATION MAGNETO DIELECTRICS
The limitation in use of dielectric material with high permittivity can be overcome by magneto-
magneto
dielectric materials. In spite of using material with high permittivity, the same miniaturization
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October December (2012), © IAEME
October-
can be obtained by using materials with moderate permittivity and permeability i.e. ε, µ > 1 , as
shown in fig. 4. Magneto-dielectric material provides control of both permittivity and
dielectric
permeability, as it can be seen in the denominator of equation (1). The base antenna is
simulated for different values of ε r and µ r where ε r /µ r > 1, ε r /µ r =1, and ε r /µ r <1. The results
are listed in table 1. From the simulation results we could find that use of magneto
. magneto-dielectric
material reduces the magnetic and electric imbalance, which enhances the system bandwidth by
increasing the amount of magnetic energy storage for a pure dielectric is capacitive. In table 1,
dielectric
for ε r /µ r =1 the impedance between dielectric and surrounding free space is much reduced,
hence bandwidth reaches maximum value. This is the advantage of magneto dielectric. For
magneto-dielectric.
ε r /µ r <1 it is seen that when permeability increases and permittivity decreases, the ability of
strong energy inside the substrate is less and so the value of radiation resistance is higher and
hence the radiation efficiency increases. Fig.4(b)-(d) shows simulated results for magneto- magneto
dielectric loaded antenna. The bold data in the table indicates relative comparison between high
permittivity loaded and magneto-dielectric loaded antennas.
dielectric
ε, µ > 1
ε r = µ r =1.74
(a) (b) (c) (d)
Figure 4.(a) ACMSA with magneto dielectrics (b) Return loss Vs Frequency (c) 2D Radiation
magneto-dielectrics
pattern (d) Efficiency Vs frequency
Table 1. Simulated parameters for base antenna, antenna with slots, antenna with dielectric
ated
constant of high permittivity, and antenna with magneto
magneto-dielectrics.
Dielectric with High
With Magneto-Dielectric : µ r × ε r = 3
Dielectric
permittivity, µ r =1
Parameters εr εr
>1 <1
Base εr εr µr εr µr
With ε r =4 =1
Antenn µr
slots =3 =5
a
2.12 1.58 0.75 0.48
Frequency (GHz) 2.2 1.95 2 1.77 1.6 2 1.77 2 2 2
Return loss (dB) 18.4 12 14.5 14.2 9.1 14.4 12.5 23 19.2 13.4
Bandwidth (MHz) 24 7 18.0 11.4 0 23.7 14.7 30 29.9 28.2
Radiation
85 76.4 85 82 79.3 87 84 85.8 85.6 83.7
efficiency (%)
Reduction in size
-- 11.5 6.8 19.8 27.6 6.8 19.8 6.8 6.8 6.8
(%)
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
– 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEME
CONCLUSION
This paper has presented some of the techniques and approaches that are commonly used for
planar antennas miniaturization using IE3D 14.65 simulation software. By varying both
permittivity and permeability of the substrate, good bandwidth and radiation efficiency can be
obtained in addition to antenna miniaturization. The antenna with magneto-dielectric material
has better bandwidth than dielectric antenna in the same size. It also presents opportunities and
challenges that new materials (magneto-dielectrics) pose for the design of small antennas.
ACKNOWLEDGEMENT
We thank the authorities of UGC, Govt. of India, New Delhi, for sanctioning IE3D 14.65
simulation software to Gulbarga University, Gulbarga. Author R.R.P would like to convey
sincere thanks to President, Principal, and Dean of Appa Institute of Engineering and
Technology, Gulbarga for constant support and encouragement for research work.
REFERENCES
[1] Balanis, C. A., “Antenna Theory Analysis and Design”. John Wiley & Sons, New
Delhi, India, 2009.
[2] Lo, T.K., Ho C.O., Hwang Y., Lam, E. K. W., and Lee, B., “Miniature Aperture-
Coupled Microstrip Antenna of very high Permittivity”. Electronics Letters, Vol. 33,
1997, pp: 9–10.
[3] Hwang, Y., Zhang, Y.P., Zheng, G.X., Lo, T.K.C., “Planar Inverted F Antenna
Loaded with high Permittivity Material”, Electronics Letters, Vol. 31, no. 20, 1995,
pp: 1710–1712.
[4] Lee J., Heo J., and Lee J., “Design of Small Antennas for Mobile Handsets using
Magneto-Dielectric Material”, IEEE Trans. Antennas Propag., 60, 2080-2084, 2012.
[5] The Inframat website (2005). “Magnetic Nanocomposite Paste: An Ideal High- µ r , k
and nanomaterial for Embedded Inductors in High Frequency Electronic Applications”,
[Online]. Available: http://www.inframat.com/press/Georgia.pdf
[6] Prasath S.D.R., et al., “Miniaturization of patch antennas using magneto-dielectric
Materials”, A Workshop on Advanced Antenna Technology, Indian Antenna Week.,
pp.1- 4, May 31-June 4, 2010.
[7] David M. Pozar, “A Reciprocity Method of Analysis for Printed Slot and Slot-Coupled
Microstrip Antennas”, IEEE Trans. Antenna Propag, Vol. AP-34, No 12, p.p. 1439-1446,
December 1986.
[8] IE3D version 14.65: Zeland Software Inc., USA, 2010.
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