CHAPTER 8

CONCLUSIONS

CONCLUSIONS

The concomitants of the research work have been ascertained in this chapter.

The cardinal motive of this proposal is to design metamaterial-inspired multiband

antenna for wireless applications. In addition to this performance enhancement of the

multiband antenna is also considered. The objectives are achieved by the design of a

triangular patch engraved with a triangular-shaped complementary split-ring resonator

along with reactive impedance surface, Frequency selective surface, and defected

ground structure.

This entire work is carried out in several stages in which five variants are

designed, fabricated, and tested. The antennas were simulated using 3D

Electromagnetic simulation software which works under the principle of the Finite

element method (FEM). Fabrication is done by means of Flame Retardant 4 (FR4)

substrate which has the benefit of low cost and easy fabrication. The fabricated

antennas are tested using a Vector network analyzer (VNA). The summary of all the

projected variants is specified in Table 8.2.

8.1 DISCUSSIONS

A triangular patch antenna incorporated with a triangular split ring resonator is

accounted as variant 1. This variant has a quad-band resonance at 3.5 GHz, 4.1 GHz,

5.6 GHz, and 9.7 GHz with the gain of 3.4 dBi, 2.7 dBi, 2.8 dBi, and 4.2 dBi. The

1
anticipated variant has satisfactory results as far as co and cross-polarization are

concerned.

Variant 2 is proposed with the dual-layered configuration in which a reactive

impedance surface is introduced between the ground plane and patch. The proposed

variant 2 resonates at seven frequencies namely 3.5 GHz, 4.3 GHz, 6.8 GHz, 7.2 GHz,

7.5 GHz, 9.1 GHz, and 9.7 GHz with the gain of 3.7 dBi, 2.6 dBi, 3.2 dBi, 2.8 dBi, 3.3

dBi, 5.1 dBi, and 6.8 dBi,

Variant 3 is designed with a superstrate configuration in which a frequency

selective surface and was set aside 10 mm above the patch. An array of crisscross-

shaped unit cells forms the superstrate. Variant 3 exhibits five resonances at 3.5 GHz,

4.1 GHz, 5.5 GHz, 9.4 GHz, and 9.8 GHz frequency bands with the gain of 4.4 dBi,

3.8 dBi, 3.7dBi, 3 dBi, and 3.9 dBi.

Variant 4 is a combined structure of reactive impedance surface and frequency

selective surface. The combinational variant exploits six resonances at 3.4 GHz, 4.2

GHz, 6.75 GHz, 7.16 GHz, 7.5 GHz, and 9.3 GHz frequency bands with the gain of

5.5 dBi, 3.7 dBi, 2.5 dBi, 2.7 dBi, 3.9 dBi, and 4.2 dBi.

The proposed Variant 5 incorporates a defective structure in the ground plane

to improve the gain of the antenna. Variant 5 is the concoction of FSS, RIS, and DGS

which exhibits six resonances at 3.2 GHz, 5.6 GHz, 6.5 GHz, 7.2 GHz, 7.5 GHz, and

9.3 GHz frequency bands with the gain of 4.7 dBi, 5.5 dBi, 2.8 dBi, 3 dBi, 2.7 dBi,

and 4.2 dBi. The fabricated prototype of all five variants is illustrated in Fig. 8.1.

2
 variant 1 (Front and back view) variant 2 (Front and back view)

variant 3 (Cross- sectional view and front view of FSS layer)

variant 4 (Cross- sectional view and view of FSS layer) variant 5 (Cross- sectional view

and DGS layer)

Fig. 8.1 Fabricated prototype of all five variants

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 The key applications of these variants1 to variant 5 are WiMAX, WLAN, Fixed &

mobile services, X- band communications. The overall gain comparison plot is

illustrated in Fig. 8.2 and the table is illustrated in Table 8.1.

Table 8.1 Overall gain comparison (All five variants)

Structure Parameters
Resonant
3.5 5.5 9.7 - - - -
Triangular patch Frequency (GHz)
antenna
Gain (dBi) 2.9 2.4 3.2 - - - -
Resonant
Triangular patch 3.5 4.1 5.6 9.7 - - -
Frequency (GHz)
antenna with
TSRR Gain (dBi) 3.3 3.7 2.8 4.2 - - -
Resonant
TSSR inspired 3.5 4.3 6.8 7.2 7.5 9.1 9.7
Frequency (GHz)
Triangular patch
antenna with RIS Gain (dBi) 3.7 2.6 3.2 2.8 3.3 5.1 6.8

Resonant
3.5 4.1 5.5 9.4 9.8 - -
TSSR inspired Frequency (GHz)
Triangular patch
antenna with FSS Gain (dBi) 4.4 3.8 3.7 3 3.9 - -

TSSR inspired Resonant

3.4 4.2 6.7 7.1 7.5 9.3 -
Triangular patch Frequency (GHz)
antenna with FSS
& RIS Gain (dBi) 5.5 3.7 2.7 2.9 3.9 4.2

Resonant
TSSR inspired 3.4 5.6 6.5 7.2 7.5 9.3 -
Frequency (GHz)
Triangular patch
antenna with
FSS, RIS & DGS Gain (dBi) 4.7 5.5 2.8 3.0 2.7 4.2

4
 6

Gain (dB)
4

-2

-4

-6 variant 0 variant 1 variant 2

variant 3 variant 4 variant 5

-8
2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5
Frequency (GHz)

Fig. 8.2 Overall gain comparison plot

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 TABLE 8.2 Summary of parameters of all the proposed variants
Parameter
Resonating Resonating
Frequency Frequency Return loss Return loss Front to
Design Peak
Simulated Measured (Simulated) (Measured) VSWR VSWR Gain directivity Bandwidth Back Beamwidth
(Simulated) (Measured) (dBi) (MHz) ratio (Degree)
(GHz) (GHz) (dB) (dB) (Mag.)
(dB)
3.5 3.5 -12.01 -10.20 1.66 1.70 3.3 2.8 122 21.3 81

variant 4.1 4.0 -11.7 15.90 1.69 1.23 2.7 2.1 166 18.5 83
1 5.6 5.5 -19.54 -15.84 1.23 1.38 2.8 3.6 167 8.2 88
9.7 9.7 -14.16 -18.87 1.40 1.26 4.2 2.09 404 8.5 78
3.5 3.5 -12.36 -12.19 1.63 1.60 3.7 2.5 220 18.1 78

4.3 4.3 -11.50 -11.49 1.72 1.68 2.6 2.7 80 14.6 71

6.8 6.6 -27.05 -16.69 1.09 1.81 3.2 4.1 560 11.2 37
variant
7.2 7.5 -11.00 -10.52 1.78 1.98 2.8 3.5 60 13.6 47
2
7.5 8.2 -28.30 -21.60 1.07 1.27 3.3 3.5 190 7.75 50
9.1 9.2 -29.60 -11.09 1.06 1.95 5.1 5.0 300 16.5 38
9.7 10.2 -22.07 -14.52 1.17 1.57 6.8 7.04 576 12.2 36
3.5 3.4 -11.50 --19.38 1.72 1.06 4.4 4.7 160 35.8 69
4.1 4.1 -10.57 -22.19 1.82 1.16 3.8 5.7 50 21.3 76
variant
5.5 5.6 -18.90 -21.45 1.23 1.19 3.7 4.24 214 12.2 46
3
9.4 9.3 -18.50 -21.09 1.29 1.98 3.0 2.3 300 5.60 48
9.8 8.6 -13.88 -26.5 1.50 1.10 3.9 2.7 280 4.51 43

6
 Parameter
Resonating Resonating Front
Frequency Frequency Peak to
Design VSWR VSWR Bandwidth
Simulated Measured Return loss Return loss Gain directivity Back Beamwidth
(Simulated) (Measured) (Simulated) (Measured) (dBi) (MHz) ratio (Degree)
(GHz) (GHz) (simulated)
(dB)
3.4 3.4 -18.47 -26.67 1.31 1.09 5.5 4.4 230 18.2 56
4.2 4.1 -14.29 -10.89 1.70 1.48 3.7 5.3 110 22.7 53
variant 6.7 5.5 -25.63 -25.57 1.14 1.58 2.5 3.0 510 5.25 40
4 7.1 7.1 -12.06 -27.23 1.70 1.65 2.7 2.6 100 11.2 47
7.5 7.5 -35.50 -14.50 1.25 1.52 3.9 4.6 210 4.75 38
9.3 9.3 -34.40 -10.99 1.11 1.75 4.2 3.6 946 4.00 52
3.2 3.2 -22.9 -19.5 1.21 1.23 4.7 3.6 680 13.4 51
5.6 5.3 -36.50 -19.87 1.24 1.27 5.5 4.8 720 9.50 43
variant 6.5 6.5 -13.40 -10.98 1.72 1.44 2.8 3.6 450 10.2 38
5 7.2 7.2 -13.09 -10.91 1.83 1.87 3.0 2.9 150 9.25 41
7.5 9.1 -13.09 -17.66 1.56 1.33 2.7 2.9 200 4.50 39
9.3 9.6 -19.20 -11.59 1.28 2.08 4.2 3.8 700 10.7 28

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8.2 VALIDATION OF THE PROPOSED WORK

To validate and ensure the results of the designed prototype, a comparative study is carried

out between this work and recent research works. The parameters like antenna size, number of

resonances, and gain of each band are considered for the study. The results of the study are presented

in Table 8.3.

TABLE 8.3 Overall comparison with existing works

Size of Frequency
the Antenna Peak gain
Reference bands covered
antenna type (dBi)
(mm2) (GHz)

Samir Salem Al-

79*46 0.9/ 2.4/ 3.5/ 5.5 Quad band 2.5 / 5.0/ 4.5/ 3.8
Bawri et al. (2019)
Reshma Roy et al.
30*30 3.6/4.9/7.4/8 Multiband 2.7/ 3.9/4.2/4.0
2020
Proposed variant 1 30*50 3.5/4.1/5.6/9.7 Multiband 3.3/ 2.7/ 2.8/ 4.2
R. Rajkumar et al. 2.4/4.1/5.2/5.8/7
28*16 Multiband 2.4/3.7/3.9/4.1/4.6
(2017) .4
N. Karthikeyan
50*50 3.3/ 4/ 4.6/7/ 7.9 Multi band 5.2/5.6/3.2/7.4/5.4
(2020)
3.5/4.3/6.8/7.2/7 3.7/2.6/3.2/2.8/3.3/
Proposed variant 2 30*50 Multiband
.5/9.1/9.7 5.1/6.8
N.Thamilselvi et al. 2.2/2.8/3.5/4.5/ 1.5/6.5/1.7/2.8/4.0/
40*40 Multiband
2020 5.5/ 6.7 2.3/
Tze-Hsuanchang et
60*60 1.5/2.5/5.2/5.8 Multiband 0.2/3.5/2.3/3.7
al. (2013)
3.5/4.1/5.5/9.4/ 2.2/ 1.7/ 1.6/ 0.85/
Proposed variant 3 30*50 Multiband
9.8 1.8
C.Elavarasi et al. 1.9/3.19/6.3/8.8/
14*16 Multiband 3.0/3.4/6.0/4.1/6.7
(2017) 11.8/15.6/18.3
R. Rajkumar et al.
25*25 2.4/5.2/7.4/8.2 Multiband 0.8/0.54/0.55/3.04
(2018)
3.4/4.2/6.7/7.1/7 3.4/ 1.62/ 0.4/0.6
Proposed variant 4 30*50 Multiband
.5/ 9.3 1.79/ 2.08
Fanjimenf et al. 2.38/2.68/2.98/
64*64 Multiband 4.3/4.5/5.6/5.4
(2019) 3.18
N.Thamilselvi et al. 2.2/2.8/3.5/4.5/ 1.5/6.5/1.7/2.8/4.0/
40*40 Multiband
2020 5.5/ 6.7 2.3/

8
 3.2/5.6/6.5/7.2/7 4.7/5.5/2.8/3.0/2.7/
Proposed variant 5 30*50 Multiband
.5/ 9.3 4.2
8.3 FUTURE SCOPE

• The current research work emphasizes single element antenna operating at multiband.

This can be extended to Multiple input and multiple output (MIMO) configuration.

• Some minor lobes have existed in the higher frequency bands, which could be

eliminated to improve the performance of the antenna further.

• All the five proposed variants are linearly polarized which may be extended for

circular polarization.

• The proposed variants are fabricated using Flame Retardant 4 (FR4) substrate due to

its low cost and easy availability. Different substrates can also experiment in the future

for various other applications.