Wireless Personal Communications
https://doi.org/10.1007/s11277-020-07324-z
Design of Metamaterial Antenna for 2.4 GHz WiFi
Applications
G. Geetharamani1 · T. Aathmanesan2
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
In this paper, Antenna is an evergreen field of research because of its never-ending demand
in the modern communication era. In this paper metamaterial antenna is presented. “Meta”
a Greek word defines “beyond” the materials provide properties beyond conventional
materials. In this paper the metamaterial and micro patch antenna concepts are combined
to improve the performance of the ordinary patch antenna. This metamaterial antenna is
designed in FR4 Epoxy substrate with dielectric permittivity of 4.4, height of the substrate
is 1.6 mm and loss tangent tan δ = 0.02 with a simple shape of rectangular patch of dimension 40 mm length and 30 mm width. This antenna is simulated in an integral based solver
simulation software called CST Microwave studio v2018 and yielded best results such as
return loss − 46.58 dB, VSWR 1.009 and bandwidth of 574 MHz, directivity is 3.379 dBi,
gain is 3.23 dBi for the resonant frequency(fr) of 2.4 GHz. The feeding network is also
designed for better integration in real time applications. This antenna is further fabricated
and tested for the validation and obtained, VSWR 1.3, Return loss − 26 dB and Bandwidth
of 200 MHz. This metamaterial antenna is suitable for 2.4 GHz WiFi applications.
Keywords Patch antenna · Metamaterial · CSRR · WiFi
1 Introduction
The expansion of wireless communication increases the research opportunities in antenna
engineering since 2.4 GHz is the ISM frequency band used for most of wireless local area
networks. Therefore, this paper focuses on design of metamaterial antenna for 2.4 GHz
applications. The definition of antenna by IEEE “an antenna as a part of a transmitting or
receiving system that is designed to radiate or to receive electromagnetic waves” micro
patch antennas are more popular form of antennas getting huge attention among the
researchers these days because of its advantages such as light weight, ease of fabrication,
low cost, low profile, portability, integrability with millimetre, and microwave circuits,
* T. Aathmanesan
cegnesan@gmail.com
1
Department of Mathematics, Anna University, Tamil Nadu, India
2
Department of ECE, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science
and Technology, Chennai, India
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G. Geetharamani, T. Aathmanesan
reduction in patch size, enhancement of bandwidth, and suppression of unwanted cross
polarized radiations of patch antenna [1].
This section deals with the basics of patch antennas, metamaterials and its applications along with the recent trends in the metamaterial antennas. The word Meta‟Greek"
means “beyond” “Metamaterials” acquire properties from their structure rather than the
composites of a material. Metamaterials are also called as Double negative materials and
left-handed materials [2]. This metamaterial concept was theoretically proposed by V. G.
Veselago in the year 1968.He theoretically proposed the possibility of a material having
simultaneous negative permittivity (ε) and negative permeability (µ) is possible [2]. This
fundamental metamaterial structure was practically proposed by Dr. John Pendry in the
year 1999.He proposed structure such as split ring resonator which act as left-handed metamaterials [3]. Metamaterials are capable for a variety of optical/microwave applications,
such as new types of beam steerers, modulators, band-pass filters, super lenses, microwave
couplers, and antenna radomes [4]. After 1999 several metamaterial structures were developed till today by the creativity of engineers and several designs leads to understand the
concept of metamaterials in a better way. This leads to a brighter future for the development of new kinds of antennas with enhanced performances. In [5] metamaterial loaded
patch antenna is discussed for WiFi Applications with the mathematical design equations
for the split ring resonator. The effects of various shapes of complementary split ring resonators (CSRR) in the performance of the patch antenna is discussed in [6]. In [7] the dipole
is integrated in a planar configuration with capacitively loaded loops (CLLs) as their nearfield resonant parasitic (NFRP) elements for Wi-Fi application is presented as a kind of
metamaterial antenna.
The effect of triangular complementary split ring resonators (CSRR) in Wi-Fi patch
antenna is presented in [8]. In [9] two metamaterial inspired split ring radiating elements
for WLAN and WiMAX applications are presented. Basic concepts in metamaterial
inspired patch antennas have been reported in [10–13]. Recent developments in WLAN
antennas discussed in [14–18]. In this paper metamaterial antenna for operating in 2.4 GHz
applications is presented. The proposed antenna consists of complementary split ring resonators (CSRR) in the rectangular patch and the modified ground structure with a proposed metamaterial structure. CST microwave studio is selected for simulation based on its
user interface which is very simple and has a capability of simulating complex structures.
CST is an electromagnetic field simulation software which is based on finite integration
technique and for analysis of metamaterial time domain solver is used. The metamaterial
antenna is further fabricated and tested in Anna University for the verification of the proposed design and the measured results are presented in Sect. 3.
This paper consists of four sections which are organized as follows: Sect. 2 includes
the design methodology, Sect. 3 contains of the discussion of results with the comparison of proposed antenna with the reference antennas, Sect. 4 completes the paper with the
conclusion.
2 Design Methodology
In this section the design methodology is presented. There are different shapes of patch
antenna are available in which the proposed antenna has simplest rectangular patch in the
front side along with two CSRRs and a metamaterial cover at the back side. Figure 1 shows
the front and back view of the proposed antenna.
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Design of Metamaterial Antenna for 2.4 GHz WiFi Applications
The dimensions for the front view of the proposed metamaterial antenna consists
of, a = 30 mm, b = 40 m, c = 27 mm, d = 20 mm, e = 18 mm, f = 8.50 mm, g = 24 mm,
h = 30 mm, i = 7 mm, j = 24 mm, k = 2 mm, l = 20 mm, m = 3.20 mm, n = 3.60 mm. The
substrate is made up of FR4 Epoxy substrate material with permittivity ε = 4.4, loss tangent tan δ = 0.02, height of the substrate h = 1.6 mm. The substrate is covered with the
double side copper cladding with electrical conductivity of 5.8e + 007 with a thickness of
t = 0.035 mm.
In the front side of the antenna the fundamental rectangular patch antenna is provided
with the complementary split ring resonator (CSRR) metamaterial structure along the sides
of the micro patch line feeding element. SRRs are compact resonating elements gives a
high-quality factor at microwave frequencies and commonly used as a metamaterial periodic structure, complementary split ring resonator structures (CSRR) loaded metamaterials
can be used to improve the isolation between array of antennas [10] and helps to achieve
better impedance matching. On the application of electric field in perpendicular direction
to the surface of the ring the current induced in the split ring resonator thereby negative
permittivity (εr) may be reflected. The layout of CSRR and equivalent circuit of the proposed CSRR [13] is shown in Fig. 2. The complementary split ring resonator structures
(CSRR) are a class of these metamaterials tend to show negative permittivity, upon electromagnetic wave intervention parallel to its axis. This rare property of CSRR is used to
modify the performance of antenna, such as gain and bandwidth enhancement and size
reduction [10].
The back side of the proposed antenna consists of the modified split ring resonator structure which helps in achieving good reflection coefficient that is the return loss
improvement is achieved due to the metamaterial structure of the ground region of the
proposed antenna. The resonant frequency (fr) of the proposed antenna is controlled by
the dimension and position of the complementary split ring resonators at the front side
and the metamaterial structure back side of the antenna. The proposed antenna is excited
by 50 ohms of impedance microstrip line inset feed since it provides better impedance
matching and the dimensions of microstrip line feed is 18 mm length and 2 mm width.
In the CST simulation environment discrete port is used for the excitation purpose. In
Fig. 1 a Front view b Back view of the proposed antenna
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G. Geetharamani, T. Aathmanesan
Fig. 2 Complementary split ring
resonator (CSRR)
the following section discussion of results obtained from simulation and measurement
is presented.
3 Results and Discussion
The proposed antenna is designed and simulated in CST Microwave studio v2018. The
parameters taken for measuring the validation of the design are reflection coefficient,
VSWR, gain, bandwidth, directivity and farfield radiation are discussed in the first part
of this section. After successful simulation of the proposed metamaterial antenna it is
then fabricated in 1.6 mm thickness FR4 Epoxy Substrate with loss tangent tan δ = 0.02
and dual layer copper with thickness 0.035 mm by using chemical etching method. The
photograph of the fabricated prototype antenna is given in Fig. 3. The second part of
this section consists of comparison of the results obtained from the proposed antenna
with the antennas in the reference works.
3.1 Reflection coefficient (S11)
In this reflection coefficient comparison plot given in Fig. 4. it is observed that the return
loss of − 46.588 dB at the resonant frequency (fr) 2.4 GHz is achieved and the − 10 dB
Fig. 3 Fabricated metamaterial
antenna
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Design of Metamaterial Antenna for 2.4 GHz WiFi Applications
Fig. 4 Reflection coefficient
Fig. 5 Voltage standing wave
ratio
bandwidth of the proposed antenna is 574 MHz in simulation. The fabricated prototype
achieves return loss of − 26 dB. The measured bandwidth value is 200 MHz and there
is a small discrepancy in return loss and bandwidth is observed due to the fabrication
losses and connector losses.
3.2 Voltage Standing Wave Ratio (VSWR)
Voltage standing wave ratio generally known as VSWR measures the quantity of mismatch between source and antenna. In case of antenna design and wireless application
VSWR must be less than 2 and expected as close to 1. The VSWR given in Fig. 5 at
resonant frequency (fr) 2.4 GHz is 1.009 during simulation and is 1.3 during measurement. This resulted value lies between 1 and 2.
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G. Geetharamani, T. Aathmanesan
3.3 Surface Current Distribution
Surface current is an important parameter to be studied because it controls the major properties of antenna such as input impedance, radiation pattern, resonant frequency and bandwidth. The surface current distribution at both top and bottom of the proposed metamaterial antenna at different frequencies is shown in Fig. 6.
From the surface current distribution, it is clear that at the resonant frequency (fr)
2.4 GHz the maximum current distribution is due to the complementary split ring resonators at the front and the metamaterial structure back side of the antenna. The intensity of
the surface current is low during the starting frequency (a) 0 GHz and reached peak value
at the resonant frequency (b) 2.4 GHz and medium at (c) 5 GHz the higher frequency level
can be seen at the surface current plots given in Fig. 6. The red region represents the highest intensity which is seen where the feeding line meets the patch structure and this distributes the surface current from the feed line to the patch structure at front side and at the
Fig. 6 Surface current distribution
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Design of Metamaterial Antenna for 2.4 GHz WiFi Applications
Fig. 7 3D radiation pattern
Fig. 8 2D radiation pattern
back side the current is distributed overall metamaterial structure and leads to the required
resonant frequency of 2.4 GHz generation.
3.4 Analysis of Radiation Pattern
The analysis of radiation pattern is important because it gives the overall information on
how the antenna radiates in the space. The three-dimensional farfield radiation pattern
at the resonant frequency (fr) 2.4 GHz is given in Fig. 7 The two-dimensional radiation
patterns mainly consist of analysing the E field and H field radiations which are given in
Fig. 8.
From the farfield plot we observed that the radiation efficiency is 2.040 dB and the total
efficiency is 2.083 dB and the directivity is 3.379 dBi and the front to back ratio is 1.9 at
the resonant frequency.
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G. Geetharamani, T. Aathmanesan
The main lobe magnitude is 3.23 dBi at the E plane and at H plane main lobe magnitude is 3.3 dBi, main lobe direction is 7 degrees and the 3 dB angular width is 88.2 degree
the side lobe level is − 1.9 dB. The radiation characteristics of the proposed metamaterial
antenna is closes to the omni directional antenna form analysing the results obtained. The
peak gain is 3.23 dBi at resonant frequency (fr) 2.4 GHz is obtained.
The three-dimensional E field pattern and H field is given in Fig. 9 both E and H Fields
can be interpreted as, (a) is at staring frequency and the minimum field generated and at
(b) maximum field with highest intensity at the resonant frequency (fr) 2.4 GHz the field is
very high at the metamaterial structure at both top and bottom of the proposed antenna. At
(c) the field generated is moderate. This can be clearly seen by the various colour representations at both E and H field.
The radiation pattern of both simulated and measured value are given in Fig. 10, measured radiation pattern characteristics are found to be in order of the simulated results make
clear that the proposed metamaterial antenna operates as expected.
3.5 Feeding Network
The simulated and measured antenna shown similar results which validates the prosed design
serves it purpose in application of WiFi communication. To improve the designed antenna
performance in further level the feeding network is developed using a simple RC network element consists of resistor with value of 1.73E-04 mH and a capacitor with 2.20E + 00 pF in
Fig. 11. The values are found to be perfect suitable values obtained from the optimisation in
Fig. 9 Field patterns
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Design of Metamaterial Antenna for 2.4 GHz WiFi Applications
Fig. 10 Comparison of simulated and measured radiation pattern
Fig. 11 Feeding network
simulation environment. The results obtained by the deign after the integration of feeding network is given below.
The return loss obtained by the antenna without feeding network is − 46.58 dB and after
addition of the feeding network it is observed that the return loss is − 115 dB. From the above
plot Fig. 12 it is clear that the performance of the proposed antenna can be doubled by using
the developed feeding network.
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G. Geetharamani, T. Aathmanesan
Fig. 12 Return loss with feeding network
4 Conclusion
In this paper, a metamaterial antenna with resonant frequency (fr) 2.4 GHz has been presented which is suitable for Wi-Fi application. The simulated antenna is also fabricated and
real time measurement is done for the validation. The results obtained from the simulation are − 46.58 dB return loss, VSWR of 1.009, 574 MHz of Bandwidth, and Directivity
of 3.379 dBi, 3.23 dBi gain with 30 × 40 mm dimension. The results obtained from the
measurement are − 26 dB return loss, VSWR of 1.3, Bandwidth of 200 MHz. The radiation characteristics are also follows the values of simulation. The feeding network was also
designed to improve the performance of the proposed antenna. In further this work may be
extended to expand the gain of the antenna different metamaterial structures.
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Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and
institutional affiliations.
Dr. G. Geetharamani is working as a Associate Professor in Anna
University. She received her Ph.D in Gandhigram Rural University,
Gandhigram. She received M.E (CSE) in Anna University, Chennai.
She received M. Phil in National College, Trichy, (Bharathidasan
University) She received M.Sc in Bharathidasan University. She
received PGDCA in Alagappa University.
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G. Geetharamani, T. Aathmanesan
T. Aathmanesan is working as an Assistant Professor in Department of
ECE, Vel Tech University Chennai, he also pursuing Ph.D. in Anna
University Chennai, He received M.Tech Degree in College of Engineering Guindy, Anna University Chennai. He completed his BE ECE
in Anna University Chennai. His area of research in Ph.D is microwave
and THz antennas.
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