Analysis and design of microstrip patch antenna loaded with ...

Research Journal of Physical and Applied Science Vol. 1(1), pp. 013 - 019, August 2012
Available online at http://www.wudpeckerresearchjournals.org
2012 Wudpecker Research Journals
Full Length Research Paper
Analysis and design of microstrip patch antenna loaded
with innovative metamaterial structure
Bimal Garg, Ankit Samadhiya, Rahul Dev Verma
Department of Electronics Engineering, Madhav Institute of Technology and Science, Gwalior, India
Accepted 20 June 2012
In this work the values of permeability and permittivity of proposed innovative metamaterial structure,
which is composed of “Array of rectangular rings with rectangular strips”, are obtained by using a
fictitious rectangular waveguide having perfect electric conductor and perfect magnetic conductor
walls. For verifying that the proposed metamaterial structure possesses negative values of Permeability
and Permittivity within the operating frequency range, Nicolson-Ross-Weir method (NRW) has been
employed. The patch antenna along with the proposed metamaterial structure is designed to resonate
at 1.47GHz. Simulation results showed that the impedance bandwidth of the RMPA is improved by
22.3MHz and return loss is reduced by 15.33dB by incorporating the proposed metamaterial structure.
For simulation purpose CST-MWS software has been used.
Key words: Impedance bandwidth, Nicolson-Ross-Weir (NRW) Rectangular Microstrip Patch Antenna (RMPA),
Return loss.
INTRODUCTION
Microstrip Patch Antennas are designed on a dielectric
substrate, which is composed of aradiating patch on one
side and ground plane on the other side as shown in
Figure 1. These are low profile, lightweight, low cost
antennas. In spite of having a lot of advantages these
antennas have some drawbacks like narrow-bandwidth,
low gain, high return loss etc. (Gupta and Dhaliwal 2011).
To overcome Patch Antenna’s drawbacksseveral
researches have been done on patch antennas. In this
area of research,Victor Veselago (1968) Engheta and
Ziolkowski (2006) introduced the theoretical concept of
metamaterials. According to the theory of Veselago, these
are generally artificial materials used to provide
properties, which are not found in readily available
materials in nature Pendry (2000) Garg et al., (2011). For
improving the performance of patch antennas (Pendry et
al., (1999) added more information. They proved that the
array of metallic wires can be used to obtain negative
permittivity and split ring resonators for negative
permeability. On the basis of this information,
*Corresponding author E-mail:
ankit.samadhiya1987@gmail.com.
Smith et al. (2001) fabricated a structure which was a
composition of split ring resonator and thin wire. It had
been observed that the structure proposed by them
possessed the negative values of permittivity and
permeability simultaneously and was named as LHM (Wu
et al., 2005) Burokur et al., 2005).
In this work “Array of rectangular rings with rectangular
strips” as a metamaterial structure has been introduced
for reducing the return loss and ameliorating the
bandwidthand directivity of the RMPA. Metamaterial
substrate size variation may affect the antenna
parameters and to see its effect on proposed antenna
parameters, variations in metamaterial substrate have
been done.
Along with these outcomes, it has been observed that
this structure satisfies the double negative property within
the operating frequency range.
ANTENNA DESIGNING PROCEDURE AND
SIMULATION RESULTS OF RMPA WITH and
WITHOUT METAMATERIAL STRUCTURE
The RMPA parameters are calculated from the formulae
given below.

Garg et al. 014
Figure 1. Microstrip Patch antenna.
values have been chosen to obtain the resonating
frequency of the proposed antenna at 1.47 GHz. These
values can be varied to change the resonating
frequency.The parameter specifications of rectangular
microstrip patch antenna are mentioned in Table 1.
Return loss S and Impedance Bandwidth of
Rectangular Microstrip Patch Antenna is shown in Figure
3. According to this figure return loss and bandwidthare -
10.447dB and 10MHz respectively.
In this paper the proposed metamaterial structure is
introduced to form the superstate of a rectangular
microstrip patch antenna (Figure 2). The required
specifications of this design are shown in the Figure 4.
Desired parametric analysis (Balanis, 1997;Stutzman
and Thiele, 1998)
Calculation of Width (W)
w =
=
Where;
c = free space velocity of light
ε r = Dielectric constant of substrate
……….. (1)
Theeffective dielectric constant of the rectangular
microstrippatch antenna.
ε =
+
The actual length of the Patch (L)
…………...(2)
L =L eff - 2ΔL ………………………………… (3)
Where
Leff =
…………………………… (4)
Calculation of Length Extension
∆
= 0.412 . .
. .
……… …(5)
The Rectangular Microstrip Patch Antenna is designed
onFR-4 lossy substrate with ε r = 4.3 and height from the
ground plane d= 1.6mm.The Length and width of RMPA
are L=47.9563mm, W=61.4295mm respectively, which
are calculated from the formulae discussed in parametric
analysis section. For cut width, cut depth, length of
transmission line and width of the feed, some specific
Nicolson-Ross-Weir (NRW) approach
The values of permittivity and permeability affect the
potential parameters like return loss and radiation pattern
of an antenna, this is the reason why these values are
calculated. For obtaining the values of permeability and
permittivity different methods can be used, some of them
are Nicolson-Ross-Weir (NRW), NISTiterative, Noniterative
and Short circuit techniques. In this work
Nicolson-Ross-Weir (NRW) technique (Mazid et al.,
2008; Ziolkowski, 2003) has been used to obtain the
values of permittivity and permeability as this is a very
popular technique to convert S-parameters due to the
fact that this technique provides easy as well as effective
formulation and calculation. All these methods discussed
above required S-parameters for obtaining the values of
permeability and permittivity.
Here in this work for extracting the S-Parameters,
proposed metamaterial structure is placed between the
two waveguide ports (Hrabar and Bartolic, 2003) Hrabar
et al., 2005) at the left and right hand side of the X axis
as shown in Figure 5. In Figure 5, Y-Plane is defined as
Perfect Electric Boundary (PEB) and Z-Plane is defined
as the Perfect Magnetic Boundary (PMB), which creates
internal environment of waveguide. The simulated S-
Parameters are then exported to Microsoft Excel
Program for verifying the Double-Negative properties of
the proposed metamaterial structure (Garg et al., 2012).
Equations used for calculating permittivity and
permeability using NRW approach (Garg et al., 2012;
Majid et al., 2009; Samadhiya and Verma, 2012)
μ = .( )
…………………………….…… (6)
..( )
Ɛ = .( )
....…………………………….. (7)
..( )
V = S + S …………………………. (8)
V = S − S …………………………. (9)

015 Res. J. Phy. and Appl. Sci.
Table 1. RMPA specifications.
Dimensions Unit
Dielectric Constant (ԑr) 4.3 -
Loss Tangent (tan ∂) 0.02 -
Thickness (h) 1.6 mm
Operating Frequency 1.9275 GHz
Length (L) 35.4413 mm
Width (W) 45.6435 mm
Cut Width 5.0 mm
Cut Depth 10.0 mm
Path Length 33.82175 mm
Width Of Feed 3.009 mm
Figure 4. Design of proposed metamaterial structure.
Figure 2. Rectangular Patch Antenna at 1.47 GHz.
Figure 5. Proposed metamaterial structure between the two
waveguide ports.
Figure 3. Simulation of Return loss S and impedance
bandwidth of Rectangular Microstrip Patch Antenna.
Where;
εr= Permittivity
μr= Permeability
c= Speed of Light
ω = Frequency in Radian
d = Thickness of the Substrate
i = Imaginary coefficient
V = Voltage Maxima
V = Voltage Minima
For satisfying Double Negative property, the values of
permeability and permittivity should be negative within
the operating frequency range. The obtained values of
these two quantities from the MS-Excel Program are
given in Table 2 and 3, whereas Figure 6 and Figure 7
shows the graph between permeability and frequency
and permittivity and frequency respectively.
Rectangular Microstrip Patch Antenna with Proposed
metamaterial is given below in Figure 8.
Return loss S and Impedance Bandwidth of Rectangular
microstrip Patch Antenna with proposed metamaterial
structure is shown in Figure 9. According to this figure
return loss and bandwidth are -25.772dB and 32.3MHz
respectively.
From Figure 3 and 9 it has been observed that the
return loss has significantly reduced by 15.33 dB and
bandwidth has increased by 22.3 MHz by incorporating
proposed metamterial structure with RMPA.
The radiation pattern of an antenna is generally its
most basic requirement because it determines the
distribution of radiated energy in to the space.Gain
depends on directivity and directivity is totally depends on
the shape of the radiation patterns of an antenna. The
Radiation Pattern of the RMPA operating at 1.47GHz is
shown in Figure 10. This shows that the directivity is

Garg et al. 016
Table 2.Obtained values for Permeability versus Frequency from the MS-Excel program.
Frequency(GHz) Permeability [µr] Re [µr]
1.4699998 -374.607339659479+3.45618384526422i -374.607
1.472 -366.919300540636+2.86948228882631i -366.919
1.474 -360.018040176235+0.731096575437185i -360.018
1.476 -354.394182884314-2.51093557285303i -354.394
1.4779998 -350.339037560325-6.30143536916735i -350.339
1.4799998 -347.928829930846-10.0203032019875i -347.929
Table 3. Obtained values for Permittivity versus Frequency from the MS-Excel program.
Frequency (GHz) Permittivity [Ɛr] Re [Ɛr]
1.4699998 -29.0168213445691-0.0961040378037559i -29.0168
1.472 -28.3655580620901-0.0176464610117287i -28.3656
1.474 -27.6834397492795+0.0364691431149244i -27.6834
1.476 -26.9840623306393+0.0534416269108215i -26.9841
1.4779998 -26.284494584046+0.0279434158733502i -26.2845
1.4799998 -25.6015651919585-0.0379574358370813i -25.6016
Figure 6. Permeability versus Frequency graph.
Figure 8. Rectangular Microstrip Patch Antenna with
proposed metamaterial structure.
Figure 7. Permittivity versus frequency graph.
6.575dBi, whereas Figure 11 shows that the directivity of
the RMPA with the proposed metamaterial structure
which is 6.604. These results are showing that there is
amelioration in directivity of RMPA by incorporating
proposed metamaterial structure.
Figure 9. Simulation of Return Loss S and
impedance bandwidth of RMPA with proposed
metamaterial structure.
Smith et al., (2000) charts play a very important role for
an antenna as it provides valuable information about

017 Res. J. Phy. and Appl. Sci.
Figure 10. Radiation pattern of a Rectangular Microstrip Patch
Antenna.
Figure 14. Fabricated rectangular microstrip patch antenna on
PCB.
Figure 11. Radiation pattern of RMPA with proposed metamaterial
structure.
Figure 15. Fabricated metamaterial structure on PCB.
Figure16. Setup for measurement of antenna parameters.
Figure 12. Smith chart of Rectangular Microstrip Patch Antenna.
Figure17. Combined simulated and measured result of proposed
antenna.
Figure 13. Smith chart of RMPA with proposed metamaterial
structure.
impedances at different frequency point so that decision
about the impedance matching can be taken. From
Figure 12 and 13, it is clear that the RMPA with the
proposed metamaterial structure provides better

Garg et al. 018
Table 4. Variation in metamaterial substrate size.
Metamaterial substrate Return Bandwidth
size (mm×mm)
Loss (dB) (MHz)
Directivity (dBi)
122.85 ×95.91 -23.923 29 6.806
120 ×94 -31.935 30.5 6.726
118 ×92 -22.041 32.9 6.429
116 ×93.4 -25.923 32.2 6.613
116×93.2 (Proposed size) -25.772 32.3 6.604
124×96 -23.489 28.9 6.809
126 ×98 -22.122 28.5 6.822
impedance matching at 1.47GHz, when compared to
RMPA alone.
In this work metamaterial substrate size has been
varied to see its effect on patch antenna parameters like
return loss, bandwidth and directivity. These variations in
metamaterial substrate size along with the values of
patch antenna parameters are shown in table 4. Initially
the dimension of the metamaterial substrate was
122.85mm ×95.91mm, which is equal to the substrate
size on which patch has been designed.It is clear from
the table 4 that, if the metamaterial substrate size is
varied then due to this variation patch antenna
parameters are also varied.
FABRICATION, TESTING AND EXPERIMENTAL
RESULTS
Return loss patternof RMPA with the proposed
metamaterial structure within the simulated frequency
range given in Figure9 has been obtained from CST-
MWS software, for verifying this result,hardware had
been fabricated on PCB. RMPA and proposed
metamaterial structure after fabrication on PCB have
been given in Figure 14 and 15.After the fabrication of
antenna the antenna parameters like return loss and
bandwidth are measured on the spectrum analyzer. The
setup which is used for antenna parameters
measurement is shown in Figure16.
Figure17 shows the Simulated and Measured result of
proposed antenna.According to this graph the return loss
and bandwidth at 1.47 GHz are -24.4dB and 29.835MHz
(approximately) for fabricated antenna. This shows that
there are very less variations in practically measured
results and simulated results of RMPA incorporated with
proposed metamaterial structure.
Conclusion
On the basis of the simulation results it is observed that
the minimum return loss obtained at the design frequency
for the RMPA with proposed metamaterial structure is -
25.77 dB and bandwidth is 32.3 MHz this is remarkable
improvement in L-band (1-2GHz), when compared to the
results of RMPA alone. It is clearly observed that the
return lossbandwidth and directivity has improved
significantly by incorporating the proposed metamaterial
structure at 3.2 mm layer from the ground plane of the
antenna. Along with these improvements this
structuresatisfies Double Negative property within the
simulated frequency range.
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