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Research Journal <strong>of</strong> Physical <strong>and</strong> Applied Science Vol. 1(1), pp. 013 - 019, August 2012<br />
Available online at http://www.wudpeckerresearchjournals.org<br />
2012 Wudpecker Research Journals<br />
Full Length Research Paper<br />
<strong>Analysis</strong> <strong>and</strong> <strong>design</strong> <strong>of</strong> <strong>microstrip</strong> <strong>patch</strong> <strong>antenna</strong> <strong>loaded</strong><br />
<strong>with</strong> innovative metamaterial structure<br />
Bimal Garg, Ankit Samadhiya, Rahul Dev Verma<br />
Department <strong>of</strong> Electronics Engineering, Madhav Institute <strong>of</strong> Technology <strong>and</strong> Science, Gwalior, India<br />
Accepted 20 June 2012<br />
In this work the values <strong>of</strong> permeability <strong>and</strong> permittivity <strong>of</strong> proposed innovative metamaterial structure,<br />
which is composed <strong>of</strong> “Array <strong>of</strong> rectangular rings <strong>with</strong> rectangular strips”, are obtained by using a<br />
fictitious rectangular waveguide having perfect electric conductor <strong>and</strong> perfect magnetic conductor<br />
walls. For verifying that the proposed metamaterial structure possesses negative values <strong>of</strong> Permeability<br />
<strong>and</strong> Permittivity <strong>with</strong>in the operating frequency range, Nicolson-Ross-Weir method (NRW) has been<br />
employed. The <strong>patch</strong> <strong>antenna</strong> along <strong>with</strong> the proposed metamaterial structure is <strong>design</strong>ed to resonate<br />
at 1.47GHz. Simulation results showed that the impedance b<strong>and</strong>width <strong>of</strong> the RMPA is improved by<br />
22.3MHz <strong>and</strong> return loss is reduced by 15.33dB by incorporating the proposed metamaterial structure.<br />
For simulation purpose CST-MWS s<strong>of</strong>tware has been used.<br />
Key words: Impedance b<strong>and</strong>width, Nicolson-Ross-Weir (NRW) Rectangular Microstrip Patch Antenna (RMPA),<br />
Return loss.<br />
INTRODUCTION<br />
Microstrip Patch Antennas are <strong>design</strong>ed on a dielectric<br />
substrate, which is composed <strong>of</strong> aradiating <strong>patch</strong> on one<br />
side <strong>and</strong> ground plane on the other side as shown in<br />
Figure 1. These are low pr<strong>of</strong>ile, lightweight, low cost<br />
<strong>antenna</strong>s. In spite <strong>of</strong> having a lot <strong>of</strong> advantages these<br />
<strong>antenna</strong>s have some drawbacks like narrow-b<strong>and</strong>width,<br />
low gain, high return loss etc. (Gupta <strong>and</strong> Dhaliwal 2011).<br />
To overcome Patch Antenna’s drawbacksseveral<br />
researches have been done on <strong>patch</strong> <strong>antenna</strong>s. In this<br />
area <strong>of</strong> research,Victor Veselago (1968) Engheta <strong>and</strong><br />
Ziolkowski (2006) introduced the theoretical concept <strong>of</strong><br />
metamaterials. According to the theory <strong>of</strong> Veselago, these<br />
are generally artificial materials used to provide<br />
properties, which are not found in readily available<br />
materials in nature Pendry (2000) Garg et al., (2011). For<br />
improving the performance <strong>of</strong> <strong>patch</strong> <strong>antenna</strong>s (Pendry et<br />
al., (1999) added more information. They proved that the<br />
array <strong>of</strong> metallic wires can be used to obtain negative<br />
permittivity <strong>and</strong> split ring resonators for negative<br />
permeability. On the basis <strong>of</strong> this information,<br />
*Corresponding author E-mail:<br />
ankit.samadhiya1987@gmail.com.<br />
Smith et al. (2001) fabricated a structure which was a<br />
composition <strong>of</strong> split ring resonator <strong>and</strong> thin wire. It had<br />
been observed that the structure proposed by them<br />
possessed the negative values <strong>of</strong> permittivity <strong>and</strong><br />
permeability simultaneously <strong>and</strong> was named as LHM (Wu<br />
et al., 2005) Burokur et al., 2005).<br />
In this work “Array <strong>of</strong> rectangular rings <strong>with</strong> rectangular<br />
strips” as a metamaterial structure has been introduced<br />
for reducing the return loss <strong>and</strong> ameliorating the<br />
b<strong>and</strong>width<strong>and</strong> directivity <strong>of</strong> the RMPA. Metamaterial<br />
substrate size variation may affect the <strong>antenna</strong><br />
parameters <strong>and</strong> to see its effect on proposed <strong>antenna</strong><br />
parameters, variations in metamaterial substrate have<br />
been done.<br />
Along <strong>with</strong> these outcomes, it has been observed that<br />
this structure satisfies the double negative property <strong>with</strong>in<br />
the operating frequency range.<br />
ANTENNA DESIGNING PROCEDURE AND<br />
SIMULATION RESULTS OF RMPA WITH <strong>and</strong><br />
WITHOUT METAMATERIAL STRUCTURE<br />
The RMPA parameters are calculated from the formulae<br />
given below.
Garg et al. 014<br />
Figure 1. Microstrip Patch <strong>antenna</strong>.<br />
values have been chosen to obtain the resonating<br />
frequency <strong>of</strong> the proposed <strong>antenna</strong> at 1.47 GHz. These<br />
values can be varied to change the resonating<br />
frequency.The parameter specifications <strong>of</strong> rectangular<br />
<strong>microstrip</strong> <strong>patch</strong> <strong>antenna</strong> are mentioned in Table 1.<br />
Return loss S <strong>and</strong> Impedance B<strong>and</strong>width <strong>of</strong><br />
Rectangular Microstrip Patch Antenna is shown in Figure<br />
3. According to this figure return loss <strong>and</strong> b<strong>and</strong>widthare -<br />
10.447dB <strong>and</strong> 10MHz respectively.<br />
In this paper the proposed metamaterial structure is<br />
introduced to form the superstate <strong>of</strong> a rectangular<br />
<strong>microstrip</strong> <strong>patch</strong> <strong>antenna</strong> (Figure 2). The required<br />
specifications <strong>of</strong> this <strong>design</strong> are shown in the Figure 4.<br />
Desired parametric analysis (Balanis, 1997;Stutzman<br />
<strong>and</strong> Thiele, 1998)<br />
Calculation <strong>of</strong> Width (W)<br />
w =<br />
<br />
<br />
= <br />
<br />
<br />
Where;<br />
c = free space velocity <strong>of</strong> light<br />
ε r = Dielectric constant <strong>of</strong> substrate<br />
……….. (1)<br />
Theeffective dielectric constant <strong>of</strong> the rectangular<br />
<strong>microstrip</strong><strong>patch</strong> <strong>antenna</strong>.<br />
ε = <br />
<br />
+ <br />
<br />
<br />
<br />
The actual length <strong>of</strong> the Patch (L)<br />
…………...(2)<br />
L =L eff - 2ΔL ………………………………… (3)<br />
Where<br />
Leff =<br />
<br />
<br />
…………………………… (4)<br />
Calculation <strong>of</strong> Length Extension<br />
∆<br />
= 0.412 . .<br />
. .<br />
……… …(5)<br />
The Rectangular Microstrip Patch Antenna is <strong>design</strong>ed<br />
onFR-4 lossy substrate <strong>with</strong> ε r = 4.3 <strong>and</strong> height from the<br />
ground plane d= 1.6mm.The Length <strong>and</strong> width <strong>of</strong> RMPA<br />
are L=47.9563mm, W=61.4295mm respectively, which<br />
are calculated from the formulae discussed in parametric<br />
analysis section. For cut width, cut depth, length <strong>of</strong><br />
transmission line <strong>and</strong> width <strong>of</strong> the feed, some specific<br />
Nicolson-Ross-Weir (NRW) approach<br />
The values <strong>of</strong> permittivity <strong>and</strong> permeability affect the<br />
potential parameters like return loss <strong>and</strong> radiation pattern<br />
<strong>of</strong> an <strong>antenna</strong>, this is the reason why these values are<br />
calculated. For obtaining the values <strong>of</strong> permeability <strong>and</strong><br />
permittivity different methods can be used, some <strong>of</strong> them<br />
are Nicolson-Ross-Weir (NRW), NISTiterative, Noniterative<br />
<strong>and</strong> Short circuit techniques. In this work<br />
Nicolson-Ross-Weir (NRW) technique (Mazid et al.,<br />
2008; Ziolkowski, 2003) has been used to obtain the<br />
values <strong>of</strong> permittivity <strong>and</strong> permeability as this is a very<br />
popular technique to convert S-parameters due to the<br />
fact that this technique provides easy as well as effective<br />
formulation <strong>and</strong> calculation. All these methods discussed<br />
above required S-parameters for obtaining the values <strong>of</strong><br />
permeability <strong>and</strong> permittivity.<br />
Here in this work for extracting the S-Parameters,<br />
proposed metamaterial structure is placed between the<br />
two waveguide ports (Hrabar <strong>and</strong> Bartolic, 2003) Hrabar<br />
et al., 2005) at the left <strong>and</strong> right h<strong>and</strong> side <strong>of</strong> the X axis<br />
as shown in Figure 5. In Figure 5, Y-Plane is defined as<br />
Perfect Electric Boundary (PEB) <strong>and</strong> Z-Plane is defined<br />
as the Perfect Magnetic Boundary (PMB), which creates<br />
internal environment <strong>of</strong> waveguide. The simulated S-<br />
Parameters are then exported to Micros<strong>of</strong>t Excel<br />
Program for verifying the Double-Negative properties <strong>of</strong><br />
the proposed metamaterial structure (Garg et al., 2012).<br />
Equations used for calculating permittivity <strong>and</strong><br />
permeability using NRW approach (Garg et al., 2012;<br />
Majid et al., 2009; Samadhiya <strong>and</strong> Verma, 2012)<br />
μ = .( )<br />
…………………………….…… (6)<br />
..( )<br />
Ɛ = .( )<br />
....…………………………….. (7)<br />
..( )<br />
V = S + S …………………………. (8)<br />
V = S − S …………………………. (9)
015 Res. J. Phy. <strong>and</strong> Appl. Sci.<br />
Table 1. RMPA specifications.<br />
Dimensions Unit<br />
Dielectric Constant (ԑr) 4.3 -<br />
Loss Tangent (tan ∂) 0.02 -<br />
Thickness (h) 1.6 mm<br />
Operating Frequency 1.9275 GHz<br />
Length (L) 35.4413 mm<br />
Width (W) 45.6435 mm<br />
Cut Width 5.0 mm<br />
Cut Depth 10.0 mm<br />
Path Length 33.82175 mm<br />
Width Of Feed 3.009 mm<br />
Figure 4. Design <strong>of</strong> proposed metamaterial structure.<br />
Figure 2. Rectangular Patch Antenna at 1.47 GHz.<br />
Figure 5. Proposed metamaterial structure between the two<br />
waveguide ports.<br />
Figure 3. Simulation <strong>of</strong> Return loss S <strong>and</strong> impedance<br />
b<strong>and</strong>width <strong>of</strong> Rectangular Microstrip Patch Antenna.<br />
Where;<br />
εr= Permittivity<br />
μr= Permeability<br />
c= Speed <strong>of</strong> Light<br />
ω = Frequency in Radian<br />
d = Thickness <strong>of</strong> the Substrate<br />
i = Imaginary coefficient<br />
V = Voltage Maxima<br />
V = Voltage Minima<br />
For satisfying Double Negative property, the values <strong>of</strong><br />
permeability <strong>and</strong> permittivity should be negative <strong>with</strong>in<br />
the operating frequency range. The obtained values <strong>of</strong><br />
these two quantities from the MS-Excel Program are<br />
given in Table 2 <strong>and</strong> 3, whereas Figure 6 <strong>and</strong> Figure 7<br />
shows the graph between permeability <strong>and</strong> frequency<br />
<strong>and</strong> permittivity <strong>and</strong> frequency respectively.<br />
Rectangular Microstrip Patch Antenna <strong>with</strong> Proposed<br />
metamaterial is given below in Figure 8.<br />
Return loss S <strong>and</strong> Impedance B<strong>and</strong>width <strong>of</strong> Rectangular<br />
<strong>microstrip</strong> Patch Antenna <strong>with</strong> proposed metamaterial<br />
structure is shown in Figure 9. According to this figure<br />
return loss <strong>and</strong> b<strong>and</strong>width are -25.772dB <strong>and</strong> 32.3MHz<br />
respectively.<br />
From Figure 3 <strong>and</strong> 9 it has been observed that the<br />
return loss has significantly reduced by 15.33 dB <strong>and</strong><br />
b<strong>and</strong>width has increased by 22.3 MHz by incorporating<br />
proposed metamterial structure <strong>with</strong> RMPA.<br />
The radiation pattern <strong>of</strong> an <strong>antenna</strong> is generally its<br />
most basic requirement because it determines the<br />
distribution <strong>of</strong> radiated energy in to the space.Gain<br />
depends on directivity <strong>and</strong> directivity is totally depends on<br />
the shape <strong>of</strong> the radiation patterns <strong>of</strong> an <strong>antenna</strong>. The<br />
Radiation Pattern <strong>of</strong> the RMPA operating at 1.47GHz is<br />
shown in Figure 10. This shows that the directivity is
Garg et al. 016<br />
Table 2.Obtained values for Permeability versus Frequency from the MS-Excel program.<br />
Frequency(GHz) Permeability [µr] Re [µr]<br />
1.4699998 -374.607339659479+3.45618384526422i -374.607<br />
1.472 -366.919300540636+2.86948228882631i -366.919<br />
1.474 -360.018040176235+0.731096575437185i -360.018<br />
1.476 -354.394182884314-2.51093557285303i -354.394<br />
1.4779998 -350.339037560325-6.30143536916735i -350.339<br />
1.4799998 -347.928829930846-10.0203032019875i -347.929<br />
Table 3. Obtained values for Permittivity versus Frequency from the MS-Excel program.<br />
Frequency (GHz) Permittivity [Ɛr] Re [Ɛr]<br />
1.4699998 -29.0168213445691-0.0961040378037559i -29.0168<br />
1.472 -28.3655580620901-0.0176464610117287i -28.3656<br />
1.474 -27.6834397492795+0.0364691431149244i -27.6834<br />
1.476 -26.9840623306393+0.0534416269108215i -26.9841<br />
1.4779998 -26.284494584046+0.0279434158733502i -26.2845<br />
1.4799998 -25.6015651919585-0.0379574358370813i -25.6016<br />
Figure 6. Permeability versus Frequency graph.<br />
Figure 8. Rectangular Microstrip Patch Antenna <strong>with</strong><br />
proposed metamaterial structure.<br />
Figure 7. Permittivity versus frequency graph.<br />
6.575dBi, whereas Figure 11 shows that the directivity <strong>of</strong><br />
the RMPA <strong>with</strong> the proposed metamaterial structure<br />
which is 6.604. These results are showing that there is<br />
amelioration in directivity <strong>of</strong> RMPA by incorporating<br />
proposed metamaterial structure.<br />
Figure 9. Simulation <strong>of</strong> Return Loss S <strong>and</strong><br />
impedance b<strong>and</strong>width <strong>of</strong> RMPA <strong>with</strong> proposed<br />
metamaterial structure.<br />
Smith et al., (2000) charts play a very important role for<br />
an <strong>antenna</strong> as it provides valuable information about
017 Res. J. Phy. <strong>and</strong> Appl. Sci.<br />
Figure 10. Radiation pattern <strong>of</strong> a Rectangular Microstrip Patch<br />
Antenna.<br />
Figure 14. Fabricated rectangular <strong>microstrip</strong> <strong>patch</strong> <strong>antenna</strong> on<br />
PCB.<br />
Figure 11. Radiation pattern <strong>of</strong> RMPA <strong>with</strong> proposed metamaterial<br />
structure.<br />
Figure 15. Fabricated metamaterial structure on PCB.<br />
Figure16. Setup for measurement <strong>of</strong> <strong>antenna</strong> parameters.<br />
Figure 12. Smith chart <strong>of</strong> Rectangular Microstrip Patch Antenna.<br />
Figure17. Combined simulated <strong>and</strong> measured result <strong>of</strong> proposed<br />
<strong>antenna</strong>.<br />
Figure 13. Smith chart <strong>of</strong> RMPA <strong>with</strong> proposed metamaterial<br />
structure.<br />
impedances at different frequency point so that decision<br />
about the impedance matching can be taken. From<br />
Figure 12 <strong>and</strong> 13, it is clear that the RMPA <strong>with</strong> the<br />
proposed metamaterial structure provides better
Garg et al. 018<br />
Table 4. Variation in metamaterial substrate size.<br />
Metamaterial substrate Return B<strong>and</strong>width<br />
size (mm×mm)<br />
Loss (dB) (MHz)<br />
Directivity (dBi)<br />
122.85 ×95.91 -23.923 29 6.806<br />
120 ×94 -31.935 30.5 6.726<br />
118 ×92 -22.041 32.9 6.429<br />
116 ×93.4 -25.923 32.2 6.613<br />
116×93.2 (Proposed size) -25.772 32.3 6.604<br />
124×96 -23.489 28.9 6.809<br />
126 ×98 -22.122 28.5 6.822<br />
impedance matching at 1.47GHz, when compared to<br />
RMPA alone.<br />
In this work metamaterial substrate size has been<br />
varied to see its effect on <strong>patch</strong> <strong>antenna</strong> parameters like<br />
return loss, b<strong>and</strong>width <strong>and</strong> directivity. These variations in<br />
metamaterial substrate size along <strong>with</strong> the values <strong>of</strong><br />
<strong>patch</strong> <strong>antenna</strong> parameters are shown in table 4. Initially<br />
the dimension <strong>of</strong> the metamaterial substrate was<br />
122.85mm ×95.91mm, which is equal to the substrate<br />
size on which <strong>patch</strong> has been <strong>design</strong>ed.It is clear from<br />
the table 4 that, if the metamaterial substrate size is<br />
varied then due to this variation <strong>patch</strong> <strong>antenna</strong><br />
parameters are also varied.<br />
FABRICATION, TESTING AND EXPERIMENTAL<br />
RESULTS<br />
Return loss pattern<strong>of</strong> RMPA <strong>with</strong> the proposed<br />
metamaterial structure <strong>with</strong>in the simulated frequency<br />
range given in Figure9 has been obtained from CST-<br />
MWS s<strong>of</strong>tware, for verifying this result,hardware had<br />
been fabricated on PCB. RMPA <strong>and</strong> proposed<br />
metamaterial structure after fabrication on PCB have<br />
been given in Figure 14 <strong>and</strong> 15.After the fabrication <strong>of</strong><br />
<strong>antenna</strong> the <strong>antenna</strong> parameters like return loss <strong>and</strong><br />
b<strong>and</strong>width are measured on the spectrum analyzer. The<br />
setup which is used for <strong>antenna</strong> parameters<br />
measurement is shown in Figure16.<br />
Figure17 shows the Simulated <strong>and</strong> Measured result <strong>of</strong><br />
proposed <strong>antenna</strong>.According to this graph the return loss<br />
<strong>and</strong> b<strong>and</strong>width at 1.47 GHz are -24.4dB <strong>and</strong> 29.835MHz<br />
(approximately) for fabricated <strong>antenna</strong>. This shows that<br />
there are very less variations in practically measured<br />
results <strong>and</strong> simulated results <strong>of</strong> RMPA incorporated <strong>with</strong><br />
proposed metamaterial structure.<br />
Conclusion<br />
On the basis <strong>of</strong> the simulation results it is observed that<br />
the minimum return loss obtained at the <strong>design</strong> frequency<br />
for the RMPA <strong>with</strong> proposed metamaterial structure is -<br />
25.77 dB <strong>and</strong> b<strong>and</strong>width is 32.3 MHz this is remarkable<br />
improvement in L-b<strong>and</strong> (1-2GHz), when compared to the<br />
results <strong>of</strong> RMPA alone. It is clearly observed that the<br />
return lossb<strong>and</strong>width <strong>and</strong> directivity has improved<br />
significantly by incorporating the proposed metamaterial<br />
structure at 3.2 mm layer from the ground plane <strong>of</strong> the<br />
<strong>antenna</strong>. Along <strong>with</strong> these improvements this<br />
structuresatisfies Double Negative property <strong>with</strong>in the<br />
simulated frequency range.<br />
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