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Wireless Personal Communications
Dual Band Notched Monopole Antenna with a Modified Ground Plane for UWBSystems
--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-notchedfunction is presented. The basic structure of the proposed monopole antenna consistsof a square radiating patch, feed-line, and a ground plane. By cutting pairs of rectangular and inverted Γ-shaped slits and also by embedding an inverted U-ringparasitic structure in the ground plane, dual band-stop performance with additionalresonances are excited and hence much wider impedance bandwidth can beproduced. In addition, the usable upper frequency of the antenna is extended from10.3 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 antennahas a small size of 12×18 mm2. Good VSWR, antenna gain, and radiation patterncharacteristics are obtained in the frequency band of interest.
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Dual Band-Notched Monopole Antennawith a Modified Ground Plane for UWBSystems
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 Γ -
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 12×18 mm 2. 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 3.1 – 10.6GHz 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
nuscriptk here to download Manuscript: Manuscript (Ojaroudi).dochere to view linked References
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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], or protruded 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- Ω SMA connector for signal transmission. The radiating patch
is connected to a feed line with width of f W and length of f L .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 d L 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 mmmm LW SubSub
1812 or about
0.15 λ × 0.25 λ 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 antenna bandwidth. As W decreases, so does the antenna bandwidth,
and vice versa. Next step, we have to determine the length of the radiating 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 which the antenna is fabricated. The important step in the design is to
choose Lresonance (the length of the resonators) which is set to resonate at 0.25 λ g .
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
Γ -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 Γ – 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 Γ -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 Γ -shaped slits. The proposed antenna with final design as shown in Fig.
9, was built and tested. Measured and simulated VSWR characteristic of the proposed 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 5.05 – 5.95 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 5.05 – 5.95 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. 2473 –2479, 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. 1317 – 11318.
[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 b ands,” 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-n otches 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 maximum gain 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 W sub L sub W f L f W W C LC
(mm) 12 18 2 7 10 11 4.5Parameter W C1 LC1 W C2 LC2 LC3 W S LS
(mm) 7.5 3.75 2 0.25 0.25 2.5 3.5Parameter W X L X W X1 L X1 W X2 W X3 L gnd
(mm) 2.25 4.75 1.8 3 0.3 0.2 3.5
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Nasser Ojaroudi was 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 theMicrowave 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 wave propagation. He is author and coauthor of more than 80 journal and international conference papersan the IEE-Trans , IEEE Letters , IET, Wiley, ACES journals 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 havemore than 200 citations with 7 h-index.
hor's picture & biographyk here to download author's picture & biography: Nasser Ojaroudi.docx
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