ANALYSIS OF WIDEBAND MONOPOLE ANTENNA WITH DEFECTED GROUND STRUCTURE FOR

X AND KU BAND COMMUNICATION APPLICATIONS

1Raghava Yathiraju, 2J Lakshmi Narayana, 3K Kumar Naik, 4B T P Madhav

1Research Scholar, Dept of ECE, K L University, AP, India 2Assistant Professor, Dept of ECE, St.Mary’s Group of Institutions Guntur

3Professor & HOD, Dept of ECE, Potti Sriramulu Chalavadi Mallikarjuna Rao

College of Engineering & Technology, Vijayawada, AP, India 4Professor, Dept of ECE, K L University, AP, India

Abstract:A defected ground structured monopole

antenna is proposed for X and Ku band communication

applications in this article. To achieve high bandwidth,

monopole antenna is added with L-shaped strips on

both sides of radiating element. The stub loaded

designed antenna is showing an impedance bandwidth

of 96% in the range of 8 to 25 GHz. The proposed

antenna is showing good radiation characteristics with

peak realized gain of more than 6 dB. In addition,

effects of added additional strips length on the

performance of the proposed antenna is also examined

and presented in this work. The simulation of the

proposed antenna is done on CST microwave studio

and a measured result of the prototyped antenna is

verified on ZNB 20 Vector Network Analyzer.

Keywords:Communication Applications; Defected

Ground Structure (DGS); Monopole Antenna;

Wideband

1. Introduction

Wideband antennas are playing vital role in the

communication applications with their high bandwidth.

Microstrip technology is one of the promising domain

to design such antennas with low profile, ease of

fabrication and capability of integration along with

microwave and millimetric wave circuits [1]. Planar

monopole antennas are best suitable devices for high

bandwidth and desirable radiation patterns. The present

challenges to the antenna engineers are to reduce the

size of the antenna and improvement of bandwidth with

no degradation in the gain and desired radiation pattern.

Many models are available in the literature regarding

bandwidth improvement and gain improvement with

probe feeding, microstrip line feeding and coplanar

waveguide feeding [2-8]. To reduce the size of the

antennas to excite additional resonance frequencies,

different methods are proposed by the researchers [9-

14]. Defected ground structure is one among them,

which can reduce the antenna size as well as excite the

additional resonance modes.

In this article, a compact and low profile,

microstrip line fed monopole antenna with defected

ground structure is presented. The design and analysis

of different iterations of the monopole antennas are

carried through commercial electromagnetic tools HFSS

and CST microwave studio. The performance

investigations of the designed models are presented in

this paper with simulation as well as measurement

results with EM-Tools and Vector network analyzer.

The proposed modeled antenna can also decrease the

large surface-wave loss and reduce its impact on the

coupling effect when it is used as an array element in

the array antenna design. The simulation and the

prototyped antenna measured data will be clearly

demonstrated in the subsequent sections.

2. Antenna geometry and configuration

The schematic configuration of the proposed

antenna and its iterations are shown in Fig. 1. Radiating

element is placed on one side of the substrate and on

the other side defected ground structure of circular slot

is taken. The ground plane under the top side of the

radiating element is working like a matching stub for

the DGS. The length of the radiating element is

calculated based on the formula in equation (1).

(5 / 4)f eff

L λ= (1)

where

min

eff

eff

c

fλ

ε=

(2)

‘c’ is the velocity of light in free space and eff

ε is the

effective dielectric constant, which is obtained from

( 1) 2eff r

ε ε= + . To design the circular slot on the

ground plane, we used the equation (3).

1/2

501 ln 1.7726

50r

Fr

h F

F h

π

πε

=

+ +

(3)

where r

ε = dielectric constant

h= height of the substrate 9

min

8.791 10

r

Ff ε

×=

(4)

where fmin = lowest frequency of the design

International Journal of Pure and Applied MathematicsVolume 115 No. 7 2017, 363-367ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu

363

The designed parameters for the proposed antenna

models are shown in table 1. A 50ohm microstrip line of

width Wf and length Lf is placed initially on the one side

of the substrate material FR4 (r

ε = 4.4). This microstrip

line is used to excite the circular slot on the ground

plane, which is working as tuning stub. By verifying the

tuning stub length, the reflection coefficient will be

affected. The dimensional characteristic of the stub

loaded notch band antenna is presented in Table 1.

(a) (b)

(c) (d)

Figure 1. Monopole Antenna Iterations, (a) Monopole

Antenna, (b) Stub Loaded Monopole, (c) Stub Loaded

Antenna with U-Slot, (d) Defected Ground

(a)

(b)

Figure 2. Notch Antenna, (a) Stub Loaded Antenna

with U-Slot, (b) U-Slot Overview

3. Results and Discussion

The reflection coefficient of the designed antenna

models is presented in Fig 3, Fig 4 and Fig 5. Fig 3

shows the reflection coefficient of monopole antenna

with defected ground structure. The monopole antenna

is showing bandwidth of 12.5 GHz and impedance

bandwidth of 78%. VSWR is also provides the

impedance matching quality along with reflection

coefficient results. VSWR will be considered for 2:1

ratio for most of the cases, but for commercial antennas

it will be taken as 1.5:1. A high VSWR is an indication

that the signal is reflected prior to being radiated by the

antenna. VSWR and reflected power are different ways

of measuring and expressing the same thing. Based on

the hundred Watt radio, a 1.5:1 voltage standing wave

ratio equates to a forward power of almost 96 watts and

a reflected power of at least 4 watts, or the reflected

power is 4.2% of the forward power. The monopole

antenna is satisfying the condition of 1.5:1 VSWR in the

operating band.

Figure 3.Reflection coefficient of Monopole antenna

Fig 4 exhibits the reflection coefficient of the stub

loaded monopole and it has been observed that the

bandwidth is improved tremendously when compared

with previous monopole antenna. An impedance

bandwidth of 96% is achieved from the stub loaded

antenna and bandwidth of 16.3 GHz.

Figure 4. Reflection coefficient of stub loaded

monopole

The reflection coefficient characteristics of all the

designed models are presented in Fig 5. Dual band

notching is obtained from the stub loaded antenna with

U-slot on the feed line. Two bands are notched from the

U-slot antenna at 12.5 to 13.5 GHz and 15 to 21GHz.

Fig 5 gives the evidence of notch bands at

corresponding frequencies and simulated VSWR at

these notch bands are greater than 2.

Figure 5. Reflection coefficient of antenna iterations

The radiated field in different directions of the

antenna can be obtained from radiation pattern curves.

Fig 6 shows the radiation of the monopole antenna at

8.2 GHz. Maximum gain of 5.7 dB is attained and the

radiation pattern is directive in this case. Fig 7 shows

the radiation pattern of the monopole antenna at 17.7

GHz and the radiation pattern is distributed with peak

realized gain of 6.22 dB.

International Journal of Pure and Applied Mathematics Special Issue

364

Figure 6. Radiation patters of monopole antenna at 8.2

GHz

Figure 7. Radiation patters of monopole antenna at

17.7 GHz

The radiation pattern of the stub loaded monopole

antenna at 9.5 GHz is shown in Fig 8. A peak realized

gain of 5.25 dB is attained and radiation pattern is

directive in nature. Radiation pattern at higher operating

frequency of 19.9 GHz is shown in Fig 9. Radiation is

quasi omni directional and gain is 6.12 dB.

Figure 8. Radiation patters of stub loaded monopole

antenna at 9.5 GHz

Figure 9. Radiation patters of stub loaded monopole

antenna at 19.9 GHz

Figure 10. Radiation patters of stub loaded monopole

antenna with u-slot at 9.5 GHz

Figure 11. Radiation patters of stub loaded monopole

antenna with u-slot at 22 GHz

Three dimensional and polar coordinates based

radiation pattern for u-slot loaded antenna at operating

bands of 9.5 and 22 GHz are shown in Fig 10 and 11

respectively. Monopole like radiation with gain more

than 5.1 dB is attained at both operating band

frequencies.

Figure 12. Current distribution of the antenna iterations

The surface current distribution of the designed

antenna models at corresponding operating bands are

presented in Fig 12. The time domain analysis results

for designed antenna models are presented in Fig 13, 14

and 15 respectively. In principle, the pulses offer

possibilities for local high-resolution interrogation of

targets or environments and for efficient transfer of

localized electromagnetic energy.

Figure 13. Time domain response of monopole antenna

Figure 14. Time domain response of monopole antenna

Figure 15. Time domain analysis response of stub

loaded monopole u-slot antenna

Figure 16. Parametric analysis with change in S1

Figure 17. Measured S11 of the antenna on ZNB 20

VNA

loss and reduce its impact on the coupling effect

when it is used as an array element in the array antenna

design. The simulation and the prototyped antenna

measured data will be clearly demonstrated in the

subsequent sections.

International Journal of Pure and Applied Mathematics Special Issue

365

4. Conclusion

Defected ground structured monopole antenna

models are proposed for X and Ku band communication

applications in this paper. The designed models of

monopole antenna and stub loaded antenna are

providing excellent bandwidth characteristics in the

wideband and U-slot loaded antenna is showing notch

band characteristics. A bandwidth of 12.5 GHz from

monopole antenna and 16.5 GHz from stub loaded

antenna is attained. Impedance bandwidth of 78% from

monopole antenna and 96% from stub loaded antenna is

also attained with VSWR<2 in the operating band. The

notch band antenna is designed to notch the Ku-band

and passing X and K-bands. The proposed antenna

models are applicable in the satellite communication

systems and capable of transmitting high data rates in

their operating band.

5. Acknowledgement

Authors thankful to department of ECE of K L

University, St. Mary’s and PSCMCE for their

encouragement and DST for the support from grants

ECR/2016/000569 and SR/FST/ETI-316/2012.

References

[1] B T P Madhav, Harish Kaza, Thanneru

Kartheek, Vidyullatha Lakshmi Kaza, Sreeramineni

Prasanth, K S Sanjay Chandra Sikakollu, Maneesh

Thammishetti, Aluvala Srinivas, and K V L Bhavani,

Novel Printed Monopole Trapezoidal Notch Antenna

with S-Band Rejection, J. Theoret. Appl. Information

Tech. ISSN: 1992-8645, 76(1) (2015), 42-49.

[2] P.Lakshmikanth, Kh Takeshore, B T P

Madhav, Printed Log Periodic dipole antenna with

Notched filter at 2.45 GHz Frequency for wireless

communication applications, J. Engg. Applied

Sciences, ISSN: 1816-949X, 10(3), (2015), 40-44,

doi: 10.3923/jeasci.2015.40.44.

[3] D S Ram Kiran, B T P Madhav, Novel compact

asymmetrical fractal aperture Notch band antenna,

Leonardo Electronic Journal of Practices and

Technologies, ISSN 1583-1078, 27(2) (2015), 1-12.

[4] M L S N S Lakshmi, Habibulla Khan and B T

P Madhav, Novel Sequential Rotated 2x2 Array

Notched Circular Patch Antenna, J. Engg. Science

and Tech. Review, ISSN: 1791-2377, 8(4), (2015),

73-77.

[5] M. V. Reddiah Babu, Sarat K. Kotamraju, B. T.

P. Madhav, Compact Serrated Notch Band MIMO

Antenna For UWB Applications, ARPN J. Engg.

Appl. Sciences, ISSN 1819-6608, 11(7) (2016), 4358-

4369.

[6] M Ajay babu, B T P Madhav, D Naga

Vaishnavi, P Radhakrishna, N Bharath, K Madhuri, K

Bhavani Prasad, K Harish, Flared V-Shape Slotted

Monopole Multiband Antenna with Metamaterial

Loading, Int. J. Comm. Ant. Propag. ISSN: 2039-

5086, 5(2), (2015), 93-97.

[7] S S Mohan Reddy, P Mallikarjuna rao, B T P

Madhav, Asymmetric Defected Ground Structured

Monopole Antenna for Wideband Communication

Systems, Int. J. Comm. Ant. Propag. ISSN: 2039-5086,

5(5), (2015), 256-262.

[8] B. T. P. Madhav, Habibulla Khan, Sarat K.

Kotamraju, Circularly Polarized Slotted Aperture

Antenna With Coplanar Waveguide Fed for Broadband

Applications, J. Engg Science and Tech., ISSN: 1823-

4690, 11(2), (2016), 267 – 277.

[9] T V Rama Krishna, B T P Madhav, G Monica,

V Janakiram, S Md Abid Basha, Microstrip Line Fed

Leaky Wave Antenna with Shorting Vias for Wideband

Systems, Int. J. Elec. Comp. Engg. (IJECE), ISSN:

2088-8708, 6(4), (2016), 1725-1731, doi:

10.11591/ijece.v6i4.10699.

[10] P Syam Sundar, Sarat K Kotamraju, B T P

Madhav, Parasitic Strip Loaded Dual Band Notch

Circular Monopole Antenna with Defected Ground

Structure, Int. J. Elec. Comp. Engg (IJECE), ISSN:

2088-8708, 6(4), (2016), 1742-1750, doi:

10.11591/ijece.v6i4.10529.

[11] T. Padmapriya and V. Saminadan, “Distributed

Load Balancing for Multiuser Multi-class Traffic in

MIMO LTE-Advanced Networks”, Research Journal of

Applied Sciences, Engineering and Technology

(RJASET) - Maxwell Scientific Organization , ISSN:

2040-7459; e-ISSN: 2040-7467, vol.12, no.8, pp:813-

822, April 2016.

International Journal of Pure and Applied Mathematics Special Issue

366

367

368