Dual Band-Notched Monopole Antenna with a Modified Ground Plane for UWB Systems

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Dual Band Notched Monopole Antenna with a Modified Ground Plane for UWB

Systems

--Manuscript Draft--

Manuscript Number: WIRE-D-13-01000

Full Title: Dual Band-Notched Monopole Antenna with a Modified Ground Plane for UWB

SystemsArticle Type: Manuscript

Keywords: Dual band-notched function, microstrip-fed antenna, modified ground plane, ultra-

wideband communications

Abstract: In this manuscript, a new compact UWB monopole antenna with dual band-notched

function is presented. The basic structure of the proposed monopole antenna consists

of a square radiating patch, feed-line, and a ground plane. By cutting pairs of

rectangular and inverted -shaped slits and also by embedding an inverted U-ring

parasitic structure in the ground plane, dual band-stop performance with additional

resonances are excited and hence much wider impedance bandwidth can be

produced. In addition, the usable upper frequency of the antenna is extended from

10.3 GHz to 13.5 GHz. The measured results reveal that the presented monopole

antenna offers a very wide bandwidth with two notched bands, covering all the5.2/5.8GHz WLAN, 3.5/5.5 GHz WiMAX and 4 GHz C bands. The designed antenna

has a small size of 1218 mm2. Good VSWR, antenna gain, and radiation pattern

characteristics are obtained in the frequency band of interest.

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Dual Band-Notched Monopole Antenna

with a Modified Ground Plane for UWB

Systems

Nasser Ojaroudi is with the Electrical Engineering Department, Germi Branch,

Islamic Azad University, Germi, Iran (E-mail: [email protected])

Abstract- In this manuscript, a new compact UWB monopole antenna with dual band-notched

function is presented. The basic structure of the proposed monopole antenna consists of a square

radiating patch, feed-line, and a ground plane. By cutting pairs of rectangular and inverted -

shaped slits and also by embedding an inverted U-ring parasitic structure in the ground plane, dual

band-stop performance with additional resonances are excited and hence much wider impedance

bandwidth can be produced. In addition, the usable upper frequency of the antenna is extended

from 10.3 GHz to 13.5 GHz. The measured results reveal that the presented monopole antenna

offers a very wide bandwidth with two notched bands, covering all the 5.2/5.8GHz WLAN, 3.5/5.5

GHz WiMAX and 4 GHz C bands. The designed antenna has a small size of 1218 mm2. Good

VSWR, antenna gain, and radiation pattern characteristics are obtained in the frequency band of

interest.

keywords: Dual band-notched function, microstrip-fed antenna, modified ground

plane, ultra-wideband communications

Introduction

There has been more and more attention in ultra-wideband (UWB) antennas ever

since the Federal Communications Commission (FCC)s allocation of the

frequency band 3.110.6GHz for commercial use [1] Designing an antenna to

operate in the UWB band is quite a challenge because it has to satisfy the

requirements such as ultra wide impedance bandwidth, omni-directional radiation

pattern, constant gain, constant group delay, low profile, easy manufacturing, etc

[2]. In UWB communication systems, one of key issues is the design of a compact

antenna while providing wideband characteristic over the whole operating band.

Consequently, a number of microstrip antennas with different geometries have

been experimentally characterized [3-4].

There are many narrowband communication systems which severely interfere

with the UWB communication system, such as the worldwide interoperability

microwave access (WiMAX) operating at 3.3-3.7 GHz and 5.35-5.65 GHz,

nuscript

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wireless local area network (WLAN) operating at 5.15-5.35 and 5.725-5.825

GHz, 3.7-4.2 GHz C-band and etc. Therefore, UWB antennas with band-notched

characteristics to filter the potential interference are desirable. Nowadays, to

mitigate this effect many UWB antennas with various band-notched properties

have developed [5-7]. Many techniques are also used to introduce notch band for

rejecting the interference in the UWB antennas. It is done either by using shunt

open-circuited stub[8], orprotruded strip [9], or step-impedance resonator (SIR)

slot [10].

All of the above methods are used for rejecting a single band of frequencies.

However, to effectively utilize the UWB spectrum and to improve the

performance of the UWB system, it is desirable to design the UWB antenna with

dual band rejection. It will help to minimize the interference between the narrow

band systems with the UWB system. Some methods are used to obtain the dual

band rejection in the literature [11-13].

In this paper, a new design of dual band-notched printed monopole antenna with

multi resonance performance is presented. The proposed antenna can operate from

2.8 to 13.5 GHz for VSWR< 2 and with rejection bands around of 3.3-4.2 GHz

and 5-6 GHz to supress any interferences from WiMAX/WLAN/C bands. The

antenna has an ordinary square radiating patch, therefore displays a good

omnidirectional radiation pattern even at higher freqteuencies. Simulated and

measured results are presented to validate the usefulness of the proposed antenna

structure for UWB applications.

Antenna Design

The structure of proposed monopole antenna fed by a microstrip line is shown in

Fig. 1. The dielectric substance (FR4) with thickness of 1.6 mm with relative

permittivity of 4.4 and loss tangent 0.018 is chosen as substrate to facilitate

printed circuit board integration. The basic monopole antenna structure consists of

a square radiating patch, a feed line, and a ground plane. The proposed antenna is

connected to a 50- SMA connector for signal transmission. The radiating patch

is connected to a feed line with width of fW and length of fL .The width of the

microstrip feed line is fixed at 2 mm, as shown in Fig. 1. On the other side of thesubstrate, a conducting ground plane ofwith width of subW and gn dL length is


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placed. Final values of the presented antenna design parameters are specified in

Table. 1.

In this work, we start by choosing the dimensions of the designed antenna.

These parameters, including the substrate, is mmmmLWSubSub

1812 or about

0.15 0.25 at 4.2 GHz (the first resonance frequency). We have a lot of

flexibility in choosing the width of the radiating patch. This parameter mostly

affects the antennabandwidth. As W decreases, so does the antenna bandwidth,

and vice versa. Next step,we have to determine the length of theradiating patch

L. This parameter is approximately4

lower , where lower is the lower bandwidth

frequency wavelength. lower depends on a number of parameters such as the

radiating patch width as well as the thickness and dielectric constant of the

substrate on whichthe antenna is fabricated. The important step in the design is to

chooseLresonance(the length of the resonators) which is set to resonate at 0.25g.

Regarding Defected Ground Structures (DGS) theory, the creating slits in the

ground plane provide additional current paths. Moreover, these structures change

the inductance and capacitance of the input impedance, which in turn leads to

change the bandwidth [6]. Therefore, by cutting a a pair of rectangular slits in the

ground plane, much enhanced impedance bandwidth may be achieved. In

addition, based on Electromagnetic Coupling Theory (ECT), by adding an

inverted U-shaped conductor-backed plane in the air gap distance, additional

coupling is introduced between the bottom edge of the square patch and the

ground plane and its impedance bandwidth is improved without any cost of size or

expense [3-4].

In the proposed design, to generate a dual band-notched property, we convert

the inverted U-shaped structure to the inverted U-ring structure, and a pair of

-shaped slits were inserted in the ground plane.At the first notched frequency

(3.8 GHz), the current concentrated on the edges of the interior and exterior of U-

shaped structure and oppositely directed between the U-ring structure and the

radiating patch. Additionally, the inseted shaped slits acts as a filtering element

to generate another notched frequency (5.5 GHz), because it can creates additional

surface current path around of ground plane. As a result, the desired high

attenuation near the notched frequencies can be produced [7-10].


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Results and Discussions

The proposed microstrip monopole antenna with various design parameters

was constructed, and the numerical and experimental results of the input

impedance and radiation characteristics are presented and discussed. The

proposed microstrip-fed monopole antenna was fabricated and tested to

demonstrate the effect of the presented. The parameters of this proposed

antenna are studied by changing one parameter at a time and fixing the others.

Ansoft HFSS simulations are used to optimize the design and agreement

between the simulation and measurement is obtained [15].

A.UWB antenna with multi-resonance characteristic

Figure 2 shows the structure of various antennas used for multi resonance

performance simulation studies. Return loss characteristics for the ordinary

monopole antenna (Fig. 2(a)), the antenna with a pair of rectangular slits in

the ground plane (Fig. 2(b)), and the antenna with a pair of rectangular slits

and coupled inverted U-shaped conductor-backed plane in the ground plane

(Fig. 2(c)) are compared in Fig 3. It is observed that by using these modified

structures in the ground plane, additional resonances are excited and hence

the bandwidth is increased. Also, Fig .4 shows the Smith Chart results for

structures that shown in Fig .2

As seen in Fig. 3, the ordinary square monopole can provide the fundamental

and next higher resonant radiation band at 4 and 7.9 GHz, respectively. The

upper frequency bandwidth is significantly affected using the pair of

rectangular slits and inverted U-shaped parasitic structure in the ground plane.

This behaviour is mainly due to the change of surface current path bychanging the dimensions of the pair of rectangular slits as shown in Fig. 5 (a).

In addition, by adding an inverted U-shaped parasitic structure in the ground

plane, the impedance bandwidth is effectively improved at the upper

frequency. As shown in Fig. 5(b), the current concentrated on the edges of

the interior and exterior of the inverted coupled U-shaped conductor-backed

plane at the extra resonance frequency (13 GHz).

B. UWB antenna with dual band-notched function


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To design a novel antenna, also in order to generate a dual band-notched

characteristic, we convert the inverted U-shaped structure to the inverted U-

ring structure, and a pair of -shaped slits inserted in the ground plane, as

displayed in Fig. 1. VSWR characteristics for the antenna with a pair of

rectangular slits and inverted U-shaped conductor-backed plane in the ground

plane (Fig. 6(a)), with a pair of rectangular slits and inverted U-ring

conductor-backed plane in the ground plane (Fig. 6(b)) and the proposed

antenna structure (Fig. 6(c)) are shown in Fig 7.As shown in Fig. 7, in order to

generate single band-notched characteristic (3.3-4.2 GHz C-Band and WiMAX),

we use an inverted U-ring conductor-backed plane. By adding a pair of -shaped

slits in the ground plane, a dual band-notched function is achieved, which covers

all the 5.2/5.8GHz WLAN, 3.5/5.5 GHz WiMAX and 4-GHz C bands [12-14].

In order to understand the phenomenon behind this dual band-stop performance,

the simulated current distributions on the ground plane for the proposed antenna at

the notched frequencies presented in Fig. 8. It is found at the notched frequencies

the current flows are more dominant around of the inverted U-ring structure and a

pair of -shaped slits.The proposed antenna with final design as shown in Fig.

9, was built and tested. Measured and simulated VSWR characteristic of theproposed antenna were shown in Fig .10. The fabricated antenna has the

frequency band of 2.8 to over 13.5 GHz with two rejection bands around 3.32-

4.23 and 5.055.95 GHz.

Measured maximum gain of the proposed antenna was shown in Fig. 11. A sharp

decrease of maximum gain in the notched frequency bands at 3.9 and 5.5 GHz are

shown in Fig. 6. For other frequencies outside the notched frequency band, the

antenna gain with the filters is similar to those without them. As illustrated, the

proposed antenna has sufficient and acceptable gain level in the operation bands.

The key in UWB antenna design is to obtain a good linearity of the phase of the

radiated field because the antenna should be able to transmit the electrical pulse

with minimal distortion [2,11]. The group delay is usually used to evaluate the

phase response of the transfer function because it is defined as the rate of change

of the total phase shift with respect to angular frequency. Ideally, when the phase

response is strictly linear, the group delay (1) is constant.

( )(1)

d wGroup Delay

dw


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From Fig. 12, it is noticed that the variation in the group delay for the antenna is

around 2 ns for the frequency range from 3.1 GHz to 10.6 GHz. There is a

variation in the group delay response at the notched bands which is due to notch

behavior of the antenna. As expected before, the groups delay variation at notches

from 3.3-4.2 GHz and 5-6GHz for WiMAX, WLAN, and C bands with respect to

other frequencies is much. In spite of it, therefore, the proposed antenna is suitable

for modern UWB communication systems.

Fig. 13 depicts the measured radiation patterns including the co-polarization and

cross-polarization in the H-plane (x-z plane) and E-plane (y-z plane). It can be

seen that nearly omnidirectional radiation pattern with low cross-polarization

level can be observed on x-z plane. The radiation patterns on the y-z plane are like

a small electric dipole leading to bidirectional patterns in a very wide frequency

band. With the increase of frequency, the radiation patterns become worse

because of the increasing effects of the cross polarization [10-14].

The transfer function is transformed to time domain by performing the inverse

Fourier transform. Fourth derivative of a Gaussian function is selected as the

transmitted pulse. Therefore the output waveform at the receiving antenna

terminal can be expressed by convoluting the input signal and the transfer

function. The input and received wave forms for the face-to-face and side-by-side

orientations of the antenna are shown in Fig. 14. It can be seen that the shape of

the pulse is preserved in all the cases. Only due to being three notches, there is a

bit distortion on received pulses which it was predictable. Using the reference and

received signals, it becomes possible to quantify the level of similarity between

signals [13].

In telecommunication systems, the correlation between the transmitted (TX) and

received (RX) signals is evaluated using the fidelity factor (2).

2 2

( ) ( )

(2)

( ) . ( )

s t r t

F Max

s t dt r t dt

Where s(t) and r(t) are the TX and RX signals, respectively. For impulse radio in

UWB communications, it is necessary to have a high degree of correlation

between the TX and RX signals to avoid losing the modulated information.

However for most other telecommunication systems, the fidelity parameter is not


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that relevant. In order to evaluate the pulse transmission characteristics of the

proposed UWB antenna with triple band-notches, two configurations (side-by-

side and face-to-face orientations) were chosen. The transmitting and receiving

antennas were placed in a d=250 mm distance from each other. As shown in Fig.

14, although the received pulses in each of two orientations are broadened, a

relatively good similarity exists between the RX and TX pulses. Using (2), the

fidelity factor for the face-to-face and side-by-side configurations were obtained

equal to 0.78 and 0.81, respectively. Values the fidelity factor show that the

antenna imposes negligible effects on the transmitted pulses. The pulse

transmission results are obtained using CST [16].

Conclusion

A novel ultra wideband antenna with dual frequency band-stop performance

is presented. The fabricated antenna has the frequency band of 2.8 to over

13.5 GHz with two rejection bands around 3.32-4.23 and 5.055.95 GHz.

Good return loss and radiation pattern characteristics are obtained in the

frequency band of interest. The proposed antenna has a simple configuration

and small size. The designed antenna can be used in UWB systems to reduce

interference between UWB and other wireless communication systems.

Simulated and experimental results show that the proposed antenna could be a

good candidate for UWB application.

References

[1] Federal Communications Commission, First report and order on ultra-wideband

technology, Washington, DC, 22nd April, 2002.

[2] D. Cheng, Compact ultra wideband microstrip resonating antenna , US

patent7872606, Jan. 2011.

[3] Z. N. Chen, Impedance characteristics of planar bow-tie-like monopole

antennas,Electronics Letters, vol. 36, pp. 1100 1101, June 2000.

[4] N. Ojaroudi, S. Amiri, and F. Geran, A novel design of reconfigurable monopole

antenna for UWB applications, Applied Computational Electromagnetics Society

(ACES) Journal, vol. 28, no. 6, pp. 633-639, July 2013.

[5] Y.S. Li, X. D. Yang, Q. Yang, and C. Y. Liu, "Compact coplanar waveguide fed ultra

wideband antenna with a notch band characteristic, "AEU - International Journal of

Electronics and Communications, vol. 65, no.11, pp. 961-966, 2011.


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[6] Ma, T.-G., Wu, S.-J, Ultrawideband band-notched folded strip monopole

antenna. IEEE Trans. Antennas Propag., vol. 55, no.9, pp. 24732479, 2007

[7] Dissanayake, T. and K. P. Esselle, Prediction of the notch frequency of slot

loaded printed UWB antennas, IEEE Trans. Antennas and Propag., vol. 55, no.

11, pp. 3320-3325, 2007.[8] C. Y. Pan, K. Y. Chiu, J. H. Duan, and J. Y. Jan, "Band-notched ultra-wideband

planar monopole antenna using shunt open-circuited stub,"Microwave and Optical

Technology Letter, vol. 53, no. 7, pp. 1535-1537, 2011.

[9] N. Ojaroudi and N.Ghadimi, UWB small slot antenna with WLAN frequency band-

stop function, Electron. Lett, 2013, 49, (21), pp. 131711318.

[10] N. Ojaroudi, M. Ojaroudi, and Sh. Amiri, Compact UWB microstrip antenna with

satellite down-link frequency rejection in X-band communications by etching an E-

shaped step-impedance resonator slot,Microw. Opt. Technol. Lett.,vol. 55, pp. 922

926, 2013.

[11] J. William, R. Nakkeeran, A new UWB slot antenna with rejection of WiMax and

WLAN bands, Applied Computational Electromagnetics Society (ACES) Journal,

vol. 25, no. 9, pp. 787-793, September 2010.

[12] M. C. Tang, S. Q. Xiao, T. W. Deng, D. Wang, J. Guan, B. Z. Wang, and G. D. Ge,

Compact UWB antenna with multiple band-notches for WiMAX and WLAN, IEEE

Trans. Antennas Propag., vol. 59, no. 4, pp. 1372-1376, April 2011.

[13] W. X. Liu and Y.-Z. Yin, "Dual band-notched antenna with the parasitic strip for

UWB,"Progress In Electromagnetics Research Letters, vol. 25, pp. 21-30, 2011.

[14] N. Ojaroudi, Sh. Amiri, and F. Geran, Reconfigurable monopole antenna with

controllable band-notched performance for UWB communications, 20th

Telecommunications Forum, TELFOR 2012, 20 22November, 2012, Belgrade,

Serbia.

[15] Ansoft Corporation, Ansoft high frequency structure simulation (HFSS), ver. 13,

Ansoft Corporation, Pittsburgh, PA, 2010.

[16] CST Microwave studio, ver. 2008. Computer Simulation Technology, Framingham,

MA, 2008.
http://digital-library.theiet.org/content/journals/10.1049/el.2013.2577http://digital-library.theiet.org/content/journals/10.1049/el.2013.2577http://digital-library.theiet.org/content/journals/10.1049/el.2013.2577http://digital-library.theiet.org/content/journals/10.1049/el.2013.2577http://digital-library.theiet.org/content/journals/10.1049/el.2013.2577http://digital-library.theiet.org/content/journals/10.1049/el.2013.2577


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Figures Caption

Figure.1.Geometry of the proposed antenna, (a) side view, (b) modified ground plane.

Figure.2. (a) Ordinary monopole antenna, (b) antenna with a pair of rectangular slits in the

ground plane (c) and with a pair of rectangular slits and inverted coupled U-shaped

conductor-backed plane in the ground plane.

Figure.3.Simulated VSWR characteristics for the various antennas shown in Fig. 2.

Figure.4. The simulated input impedance on a Smith Chart of the various antenna structures

shown in Fig. 2

Figure.5.Simulated surface current distributions on ground plane for (a) antenna with a pair

of rectangular slits 11.7 GHz, and (b) the square monopole antenna with a pair of rectangular

slits and inverted coupled U-shaped conductor-backed plane at 13 GHz

Figure.6.(a) Antenna with a pair of rectangular slits and inverted U-shaped conductor-backed

plane in the ground plane, (b with a pair of rectangular slits and inverted U-ring conductor-

backed plane in the ground plane (c) and the proposed antenna structure.

Figure.7.Simulated VSWR characteristics for the various antenna structures shown in Figure.

6.

Figure.8.Simulated surface current distributions on ground plane for the proposed antenna at

the notched frequencies, (a) 3.9 GHz (b) 5.5 GHz.

Figure.9.Photograph of the realized printed monopole antenna, (a) top view, and (b) bottom

view.

Figure.10.VSWR comparison of the proposed antenna.

Figure.11.Measured maximumgain versus frequency for the proposed antenna.

Figure.12.Measured and simulated group delay for the proposed antenna.

Figure.13.Measured radiation patterns of the proposed antenna (a) 4.5 GHz, (b) 8.5 GHz, and

(c) 12.5 GHz.

Figure.14.Transmitted and received pulses (a) side bye side and (b) face to face.

Table. 1.Final dimensions of proposed antenna.


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Figure. 1

Figure. 2


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Figure. 3

Figure. 4


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Figure. 5

Figure. 6


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Figure. 7

Figure. 8


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Figure. 9

Figure. 10

Figure. 11


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Figure. 12

Figure. 13


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Figure. 14

Table. 1

Parameter Wsub Lsub

Wf Lf

W WC LC

(mm) 12 18 2 7 10 11 4.5

Parameter WC1 LC1

WC2 LC2

LC3 WS

LS

(mm) 7.5 3.75 2 0.25 0.25 2.5 3.5

Parameter WX LX WX1 LX1 WX2 WX3 Lgnd

(mm) 2.25 4.75 1.8 3 0.3 0.2 3.5


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Nasser Ojaroudiwas born on 1986 in Germi, Iran. He received his B.Sc. degreein Electrical Engineering from Azad University, Ardabil Branch, Iran and M.Sc.

degree in Telecommunication Engineering from Shahid Rajaee University,Tehran, Iran in 2011 and 2013 respectively. From 2013, he is working toward thePh.D. degree at the Iranian Research Organization for Science and Technology,Tehran, Iran. Since March 2008, he has been a Research Fellow in the

Microwave Technology (MWT) Company, Tehran, Iran. His research interestsinclude ultra-wideband (UWB) microstrip antennas and band-pass filters (BPF),

reconfigurable structure, design and modeling of microwave device, and electromagnetic wavepropagation. He is author and coauthor of more than 80 journal and international conference papersan theIEE-Trans,IEEE Letters,IET, Wiley, ACESjournals and etc. Also he is a member and reviewerin some journals and conferences such as the Applied Computational Electromagnetic Society (ACES)

journal, The International Journal for Computation and Mathematics in Electrical and ElectronicEngineering (COMPEL), and the African Journal of Estate and Property Management. His papers have

more than 200 citations with 7 h-index.

hor's picture & biography

k here to download author's picture & biography: Nasser Ojaroudi.docx
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Dual Band-Notched Monopole Antenna with a Modified Ground Plane for UWB Systems

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