Engineering Science and Technology, an International Journal 20 (2017) 18–27

Contents lists available at ScienceDirect

Engineering Science and Technology,

an International Journal
journal homepage: www.elsevier.com/locate/jestch

Full Length Article

Design and investigation of sectoral circular disc monopole fractal

antenna and its backscattering
Raj Kumar ⇑, Nagendra Kushwaha
ARDE, Dr. Homi Baba Road, Pune 411 0 21, India

a r t i c l e i n f o a b s t r a c t

Article history: This article presents the design of sectoral circular disc fractal antenna. The proposed antenna has been
Received 13 January 2016 excited using CPW – feed. The measured result of this antenna offers the ultra wideband characteristics
Revised 2 June 2016 from 3.265 GHz to 15.0 GHz. The measured and simulated results are compared and found in good
Accepted 4 July 2016
agreement. The impedance match of the antenna throughout the band is improved by incorporating
Available online 20 August 2016
the rectangular slots in the ground plane. The measured radiation patterns of this antenna are nearly
omni-directional in H-plane and bidirectional in E-plane. The backscattering of antenna is also discussed
Keywords:
and calculated for antenna mode and structural mode scattering. This type of antenna is useful for UWB
Microstrip antenna
Monopole antenna
system, microwave imaging and vehicular radar, precision positioning location.
Fractal geometry Ó 2016 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC
CPW-feed BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
UWB system

1. Introduction geous for wide bandwidth and good radiation patterns and easily
integrated with MIC/MMICs.
With the tremendous advancement in wireless communication The miniaturization of antennas along with bandwidth
systems, there is an increasing demand for miniature, low-cost and enhancements are the two main challenges in UWB antenna
easy-to-fabricate ultra wideband antennas. The ultra wideband design. Recently, fractal geometries have been reported as a
(UWB) spectral range declared in February 2002 by the FCC is from promising research area in the design of UWB compact antennas
3.1 GHz to 10.6 GHz [1]. The UWB system has the advantages of and also advantageous for good impedance matching. Fractal
transmitting high data rate with low power consumption. The geometries are characterized by self-similarity and space filling
UWB system requires an UWB antenna of small size. It is difficult properties. These properties of fractal can be used in the design
to design an antenna of compact size with the characteristics of of various type of antennas and microwave circuits. Self-
omni-directional radiation patterns, constant group delay and similarity offers the multiband properties or UWB feature of an
phase linearity. In the open literature, many researchers have antenna while spacing filling properties make the antenna/circuit
reported UWB monopole antennas designed on both non-planar miniaturized. The multi frequency properties of fractals when used
and planar structures. A non-planar UWB antenna has been as radiating structures were first reported in [8]. Fractals might
reported in [2] while an UWB planar monopole antenna with direct also join some of the early designs based on self scaling properties
probe feed reported in [3]. However, these antennas exhibit UWB however they are of bigger size [9]. Puente et al. first reported the
characteristics with a bigger overall size and cannot be easily inte- behaviour of a fractal multiband antenna i.e. Sierpinski monopole
grated with MIC/MMIC devices. Some researchers have reported [10]. Some steps further in the field of multiband fractal antennas
UWB antennas with partial ground plane microstrip feed [4,5] were published in [11–13]. Fractal antennas with multiband prop-
and with coplanar waveguide (CPW) – feed [6,7]. The CPW-feed erties have also been reported in [14]. The multiband resonances
has many advantages in comparison with partial ground micro- generated using the defected ground structure (DGS) and DGS
strip feed such as no double side printing, no alignment problem effects on size reduction of antenna and Mutual coupling of arrays
and low losses at higher frequencies. A CPW-feed is also advanta- is reported in [15]. But multiband exhibits by DGS are narrow
bandwidth and complex to adjust the bands into the useful appli-
cations. The bandwidth enhancement of antenna by employing the
⇑ Corresponding author. fractal geometry with gap coupling has also been shown [16]. The
E-mail address: raj34_shivani@yahoo.co.in (R. Kumar). proposed antenna is coaxially feed and bandwidth has been
Peer review under responsibility of Karabuk University. enhanced by merging the multiple resonances but size of antenna

http://dx.doi.org/10.1016/j.jestch.2016.07.001
2215-0986/Ó 2016 Karabuk University. Publishing services by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27 19

is bigger than the reported monopole antenna. Present author [17] with the angle 120°. In the first iteration, four equilateral triangles
has reported monopole antenna to achieve the UWB and dual of side length 5 mm are inserted and subtracted from the zeroth
polarization by implementing slot in patch and ground plane. iteration. This becomes the first iteration of the antenna. For the
Some planar monopole fractal antennas using partial microstrip second iteration, four equilateral triangles with side length of
feed and CPW – feed for UWB bandwidth were reported in [18– 3.175 mm are inserted in the second iterative structure and sub-
21]. Currently, fractal geometry is also being combined with Meta- tracted. This is called the second iteration. For the third iteration,
material (MTM) and has become a hot topic in antenna and micro- four equilateral triangles of side length 2.0161 mm are inserted
wave circuits research. For instance, fractal perturbation in CSRRs and subtracted from the second iteration. This is called the third
results in a significant lower resonance [22,23], multiband beha- iteration. For the fourth iteration, again four equilateral triangles
viour [24], and broadband performance [25]. Others researchers with side length of 1.28 mm are inserted and subtracted from
also introduced the Hilbert curve in artificial magnetic materials the third iteration. This becomes the fourth iteration of antenna.
[26], and some authors even exploited fractal concept for elevation For the fifth iteration, four equivalent triangles with side length
of pass band performance in UWB filter [27]. of 0.81294 mm are inserted and subtracted from the fourth itera-
In this paper, fractal geometry on circular disc sectoral mono- tion. This becomes the fifth iteration of the antenna and the struc-
pole antenna has been exploited to achieve the ultra wide band- ture of the final proposed antenna. The same process can not be
width. Antenna with fractal geometry is advantageous for good repeated to the infinite iteration because of fabrication constraints.
impedance matching and good RCS also. The RCS of UWB fractal Here, the final antenna structure is taken with five iterations. Four
antenna is necessary to study because antenna scattering is the equilateral triangles are present in each iteration and each of them
main contribution to the total radar cross section (RCS) of low- is placed with 30° difference. The first equilateral triangle is
observable platforms. The antenna scattering is related with its rotated by 30°, the second is rotated by 60°, the third is rotated
feed port, which affects the design of antenna with low RCS and by 90°, and the fourth is rotated by 120°. These equilateral trian-
good radiation characteristic simultaneously [28–30]. Therefore, gles are inscribed into the cylinder in each iteration. The radii of
scattering behaviour of antennas is important for defence applica- the cylinders in various iterations are 15.0 mm, 10.654 mm,
tions. In fact, antenna scattering can be a source of electromagnetic 7.44 mm, 5.258 mm, 3.753 mm, and 2.73 mm respectively in the
compatibility problems and can cause interference with other sys- decreasing order of the iteration. The central metal parts of the
tems on the same platform. Wide usages of fractal antennas make equilateral triangles are removed to form the fractal geometry.
sense in the RCS study and its reduction for antenna designer. The This final proposed antenna has been fed with CPW-feed as
RCS reduction of fractal antenna in narrow band has been reported shown in Fig. 1 and it has been designed on a substrate of dielectric
in [31]. But RCS reduction of multiband or UWB fractal antenna has constant er = 4.3 and thickness 1.53 mm. The size of the antenna
not been reported in the open literature. structure is 32.5 mm
37.46 mm. The width of the CPW-feed
This paper presents the design of UWB fractal monopole antenna has been taken W = 2.8 mm and spacing between feed and ground
followed by a discussion on its backscattering properties. The pro- is 0.6 mm. This makes the feed line’s characteristic impedance
posed fractal antenna is excited with CPW – feed and studied with Z0 = 50 X. Thus, it can be connected with a 50 X SMA connector
respect to the various design parameters and their effect on its impe- directly. The length and the width of the ground planes for the
dance bandwidth. The proposed antenna is also validated experi- CPW – feed are optimized at 15.5 mm and 22.73 mm respectively.
mentally. This antenna is characterized in terms of impedance The overall dimension of the substrate is 35.0 mm
50.0 mm. The
bandwidth, radiation patterns, group delay and backscattering. proposed antenna is shown in Fig. 1 with optimized dimensions.

2. Fractal geometry of the proposed antenna 3. Simulated results

The proposed antenna has been designed for UWB characteris- The proposed antenna has been simulated for each of the design
tics. The antenna is made using an iterative structure as shown in parameters which affect the performance of the antenna. The gap
Fig. 1. In the zeroth iteration, a cylinder of radius 15 mm is taken between the patch and the ground plane, the gap between the
ground and the feed line, the length and width of the ground plane,
all are critical parameters which have an influence on the antenna
bandwidth. This is because the current distribution is at the edges
of the patch and along the upper edges of the ground plane as
shown in Fig. 2. So, the gap between the patch and the ground
plane is critical to achieve UWB characteristics. The length of the
ground plane is also important for monopole antenna. It should
be around quarter wavelength k/4. To accommodate the effect of
substrate and fractal geometry, the length of the ground has to
be optimized. The ground width of the proposed antenna has also
been optimized for optimum performance. The gap between the
feed and the ground is optimized for proper input impedance
matching throughout the band.

3.1. Effect of gap between the patch and ground plane

The proposed antenna has been simulated for various gap

between the patch and the ground plane. The simulated results
of gap from 0.1 mm to 0.5 mm with the step of 0.1 mm are shown
in Fig. 3. It is observed from the simulated results that as the gap
decreases from 0.5 mm to 0.3 mm, the impedance matching
Fig. 1. Proposed fractal antenna with CPW – feed. improves. But a good impedance matching throughout the band
20 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27

Fig. 2. Current distribution on the proposed fractal antenna.

Fig. 3. Simulated results of proposed antenna for various gap between patch and ground plane (Gpg).

is achieved at the gap 0.3 mm. It is observed for gap 0.2 mm and characteristic. From the optimization, the width and length of
0.1 mm that the impedance matching deteriorates at higher fre- the slot are fixed at 5.0 mm and 4.0 mm. The simulated results
quency side. with the optimized slot and without the slot are compared as
shown in Fig. 5.
3.2. The effect of the slot in ground plane
3.3. Effect of the ground plane width (GW)
The effect of slot in the ground plane has been simulated. It is
noticed from the simulated results that the return loss improves In a CPW-feed, on both sides of the feed rectangular ground
due to slot in the ground plane at higher frequency as shown in planes are placed. The width of the rectangular ground plane
Fig. 4. The impedance matching improves at higher frequency by (GW) is important because current distribution is along the x-axis
5 dB. The size of the slot has been optimized to achieve the UWB of the ground plane as shown in Fig. 2 at 5 GHz and 8.2 GHz. The

Fig. 4. Simulated results of proposed antenna with and without slots in ground plane.
 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27 21

Fig. 5. Simulated results of proposed antenna with various values of ground plane width (Gw).

effect of the ground width has been simulated for various values of observed at higher frequency side in terms of bandwidth. It indi-
ground width. The simulated results for different ground plane cates that the ground length does not affect considerably the band-
widths are shown in Fig. 5 with the values varying from width of the antenna.
22.73 mm to 24.73 mm with a step of 1.0 mm. Here, all other
parameters are kept fixed (Gpg = 0.3 mm, GL = 20.5 mm, Gfg = 0.6 -
mm and W = 2.8 mm). It is noticed that, as the ground width 4. Experimental results and discussions
(GW) increases from 22.73 mm to 24.73 mm, the lower end fre-
quency shifts towards the lower side. There is an optimum value The proposed fractal antenna with the optimized dimension is
of width which offers the impedance bandwidth throughout the shown in Fig. 1. The antenna has been fabricated with these opti-
band. This is because the ground width behaves like an inductive mized dimensions with and without the slot. The photograph of
resonant circuit over which the current is distributed along the the proposed fractal antenna with and without the slot is shown
X-axis. As the ground width increases or decreases, the inductive in Fig. 7. The antenna has been tested using vector network ana-
reactance also increases or decreases. But at the optimum ground lyzer R & S VNA ZVA40. The experimental result of the proposed
width value, this inductive part is minimum. It means the ground antenna with the slot exhibits UWB characteristics from
width of a CPW-feed monopole antenna plays an importance role 3.265 GHz to 15 GHz. The antenna has been simulated using HFSS
in achieving the ultra wide bandwidth of the antenna. software based on the finite element method and CST MW Studio
based on the finite integration method. The experimental and sim-
ulated results are in good agreement as shown in Fig. 8. This
3.4. Effect of the ground plane length (GL) antenna is fed with CPW-feed and two rectangular slots in the
ground planes have been incorporated to improve the return loss
The effect of the ground plane length is also simulated using 3D at higher frequency. This gives the 4–5 dB improvement in the
electromagnetic simulator HFSS. The simulation has been carried return loss around 9 GHz. In the proposed fractal antenna, the frac-
out for the ground length (GL) from 15.5 mm to 17.5 mm with a tal geometry is incorporated in the solid sectoral circular disc of
step of 1 mm keeping all other parameters fixed; Gw = 22.73 mm, radius 15 mm. It means the length of the monopole formed is
Gpg = 0.3 mm, Gfg = 0.6 mm and W = 2.8 mm. The simulated results 15 mm which gives the first resonance corresponding to k = l/4 at
are shown in Fig. 6. It is observed from the simulated results, as the around 5 GHz. A circular disc monopole of 15 mm diameter will
ground length increases the lower end frequency shifts slightly also give the fundamental frequency at around 5 GHz. But the dif-
towards the lower frequency side. No major effect has been ference between the 15 mm diameter circular disc monopole and

Fig. 6. Simulated results of the proposed antenna with various values of ground plane length.
22 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27

Fig. 7. (a) Photograph of proposed fractal antenna (b) photograph of fractal antenna without slot.

Fig. 8. Experimental and simulated results of proposed fractal antenna with slot.

the 15 mm sectoral circular disc monopole is better impedance The fractal antenna without the slot and with ground width
matching achieved with the latter. The 15 mm sectoral disc mono- Wg = 24 mm and length GL = 17 mm has also been tested. The mea-
pole exhibits better impedance matching because of flaring with sured and simulated results (from HFSS and CST software) are in
120° angle. Incorporating the fractal geometry in the present struc- good agreement as shown in Fig. 9. It is clear that without the slot
ture further enhance the impedance matching. As shown in Fig. 8, and optimum ground width, the return loss is not below – 10 dB
this antenna resonates at multiple resonance frequencies (modes) throughout the band. The measured and simulated results indicate
i.e. 4.75 GHz, 6.42 GHz, 8.1 GHz, 9.1 GHz and 11.5 GHz. These mea- the visible effect of slot as well as ground width.
sured resonance frequencies are almost in good agreement with The radiation patterns of the proposed fractal antenna have been
the simulated multiple resonance frequencies from HFSS and CST measured at selective frequencies in an in-house anechoic cham-
software. These multiple resonance frequencies merge with each ber. The radiation patterns in the H-plane were measured at
other and give the overall UWB bandwidth. frequencies 4.7 GHz, 6.0 GHz, 8.0 GHz, 7.8 GHz, 9.8 GHz and

Fig. 9. Experimental and simulated results of fractal antenna without slot.

 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27 23

12.0 GHz as shown in Fig. 10a. Similarly, radiation patterns in the E- in both the planes are merged and compared. The measured and
plane were also measured at frequencies 4.7 GHz, 6.0 GHz, 8.0 GHz, simulated radiation patterns are in close agreement. The nature of
9.8 GHz and 12.0 GHz as shown in Fig. 10b. The radiation patterns radiation patterns are nearly omni-directional in the H-plane and
in the H- and E-planes were also simulated using HFSS and CST bidirectional in the E-plane. It is observed that as the frequency
Microwave Studio. The measured and simulated radiation patterns increases, the radiation patterns slightly vary. This may be because

Fig. 10a. Measured and simulated H (XZ) – plane radiation patterns of proposed fractal antenna with slot.

Fig. 10b. Measured and simulated E (YZ) – plane radiation patterns of proposed fractal antenna with slot antenna.
24 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27

of edge reflection, fractal nature of the antenna and lossy dielectric sured and simulated using both the software as shown in Fig. 11. A
constant. The simulated HFSS and CST radiation patterns in the H- close agreement between the measured and simulated radiation
and E-planes also slightly vary. This difference in the radiation pat- patterns were also found for the antenna without slot. The radiation
terns is due to the fact that both the software are based on different patterns of the antenna with slot are more stable than for the
numerical techniques. The radiation patterns in the E and H-plane antenna without the slot throughout the band. The ripple in the
for the antenna without the slot in the ground plane were also mea- radiation patterns are more in antenna without the slot. This is

Fig. 11a. Measured and simulated H (XZ) – plane radiation patterns of fractal antenna without slot.

Fig. 11b. Measured and simulated E (YZ) – plane radiation patterns of fractal antenna without slot.
 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27 25

Fig. 12. Measured and simulated peak gain of fractal antenna with and without slot.

5. Group delay and phase variation of the proposed antenna

One of the performance indicators for an ultra wideband

antenna is the group delay which should be constant throughout
the operating band to ensure minimum distortion in signal trans-
mission. Mathematically, the group delay (s) can be calculated by
taking negative derivative of the transmission phase U(f) with
respect to frequency f
d/ðf Þ
Group delay; s¼ ð1Þ
2pdf
The group delay of the antenna is simulated by putting two
identical antennas in far-field region. The simulated group delay
Fig. 13. Simulated radiation efficiency of proposed antenna.
of the antenna is shown in Fig. 14. It is seen that in the UWB region,
the group delay variation is very small and almost constant
because the return loss of the antenna without the slot is poor at throughout the band. This indicates UWB antenna system will have
higher frequency beyond 9.5 GHz. a very less distortion in received signal.
The peak gain of the proposed fractal antenna with and without
the slot in the ground plane is measured and simulated using both 6. Backscattering results of proposed antenna
the HFSS and CST software. The measured peak gain with and
without the slot are compared with the simulated peak gain as The RCS of an antenna is dependent on its feed termination. The
shown in Fig. 12. The peak gain of the proposed antenna increases monostatic RCS with open circuit, short circuit and matched – load
as the frequency increases. This is because the effective area of the (50 X) terminations are simulated in graphical as well as tabulated
antenna increase as the wavelength becomes shorter at higher fre- form using HFSS software. These simulated results of RCS with
quency. But beyond a certain higher frequency, it does not vary open circuit, short circuit and matched load terminations are used
because of an increase in the loss of the substrate and cross polar- to calculate the RCS of structural mode scattering and antenna
ization. The measured peak gain of the antenna without the slot mode scattering using Eqs. (2) and (3) respectively [30].
decreases beyond the frequency 9.5 GHz. This is due to poor return The structural mode scattering (rs ) is calculated using
loss at this frequency. The simulated radiation efficiency of the  pffiffiffiffiffiffi pffiffiffiffiffiffiffi 2
ð r0 þ rsh Þ
proposed antenna with slot is shown in Fig. 13. The efficiency is rs ¼  
 ð2Þ
around more than 70% throughout the band. There is a reduction 2
in the efficiency with an increase in the frequency which is due where, r0 and rsh are the RCS with the open and short circuit termi-
to an increase in the frequency dependent dielectric and copper nation. The antenna mode scattering (ra) is calculated using
losses.
26 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27

Fig. 14. Simulated group delay of proposed fractal antenna.

tional in H-plane and bidirectional in E-plane. The group delay of

the antenna has a negligible variation in the operating band. The
monostatic RCS of the antenna is also studied for both the antenna
scattering mode and the structural scattering mode. The RCS of the
fractal antenna is good in the operating band. This makes this
antenna a potential candidate for military applications. The pro-
posed antenna is compact, simple to design and easy to fabricate
and integrate with MMIC devices. The antenna is useful for UWB
systems, medical imaging and vehicular radar for civil as well as
defense applications.

References

[1] International Telecommunication Union, Radio Communication Study Groups,

‘‘Framework for the introduction of devices using ultra-wideband technology”,
Document 1/85(Rev. 1)-E, 09, Nov. 2005.
Fig. 15. Simulated monostatic RCS for antenna mode scattering of proposed fractal [2] K.P. Ray et al., Broadband planar rectangular monopole antennas, Microwave
antenna. Opt. Technol. Lett. 8 (1) (2001).
[3] M. Hammoud, P. Poey, F. Colombel, Matching the input impedance of a
broadband disc monopole, Electron. Lett. 29 (4) (1993) 406–407.
pffiffiffiffiffiffi pffiffiffiffiffiffiffi2 [4] J. Jung, W. Choi, J. Choi, A small wideband microstrip-fed monopole antenna,
 r0  rsh 
ra ¼  
 ð3Þ
IEEE Microwave Wireless Compon. Lett. 15 (2005) 703–705.
[5] M.K. Kim, K. Kim, H. Suh, I. Park, A T-shaped microstrip line-fed wide slot
2
antenna, IEEE Antennas Propag. Soc. 3 (2000) 1500–1503.
It is observed from the simulated results that the RCS of struc- [6] J. Liang, C. Chiau, C.D. Chen, C.G. Parini, Study of a printed circular disc
monopole antenna for UWB systems, IEEE Trans. Antennas Propag. 53 (2005)
tural mode scattering of the proposed antenna is largely reduced at 3500–3504.
the high frequency range, which is due to the relatively small [7] M.R. Haji-Hashemi, M. Mir-Mohammad Sadeghi, V.M. Moghtadai, Space-filling
wavelength in comparison to the geometrical size of the antenna. patch antennas with CPW feed, Prog. Electromagn. Res. Symp. (2009).
[8] C. Puente, R. Pous, Fractal design of multiband and low side-lobearrays, IEEE
In the low frequency range, RCS is large because the scale of the Trans. Antennas Propagat. 44 (1996) 1–10.
proposed fractal antenna is similar to the incident wavelength. [9] H.O. Peitgen, H. Jürgens, D. Saupe, Chaos and Fractals, Springer-Verlag, New
Here, all the monostatic RCS are calculated for vertical polarization, York, 1990.
[10] C. Puente, J. Romeu, R. Pous, X. Garcia, F. Benitez, Fractal multiband antenna
i.e., both the incident and received electric fields are oriented along
based on the Sierpinski gasket, Electron. Lett. 32 (1996) 1–2.
h = 0 and U = 0. [11] C. Puente, J. Romeu, R. Bartoloḿe, R. Pous, Perturbation of the Sierpinski
The antenna mode and structural mode RCS of the proposed antenna to allocate operating bands, Electron. Lett. 32 (1996) 2186–2188.
[12] C. Puente, J. Claret, F. Sagúes, J. Romeu, M.Q. López-Salvans, R. Pous, Multiband
fractal antenna versus frequency is shown in Fig. 15. The proposed
properties of a fractal tree antenna generated by electrochemical deposition,
fractal antenna RCS throughout the band is around 28 dB with Electron. Lett. 32 (1996) 2298–2299.
impedance matching throughout the band. The RCS of structural [13] C. Puente, Fractal antennas (Ph.D. dissertation) Dept. Signal Theory
scattering mode is same as the RCS with matched termination. This Communicat., Universitat Politécnica de Catalunya, 1997.
[14] Nathan Cohen, Fractals: a new era in military antenna design, RF Des. (2005)
indicates the potential of the proposed fractal antenna structure to 12–17.
be used for military applications for transmitting/receiving the [15] Anshika Khanna, Anshika Srivastava, Jai Prakash Saini, Bandwidth
high data rate secure wireless communications. enhancement of modified square fractal microstrip patch Antenna using gap
– coupling, JESTCH 18 (2015) 286–293.
[16] Munish Kumar, Vandana Nath, Analysis of low mutual coupling compact
multiband microstrip patch antenna and its array using difected ground
7. Conclusions structure, Eng. Sci. Technol. Int. J. 19 (2016) 866–874.
[17] R.V.S. Ram Krishna, Raj Kumar, A slotted UWB monoople antenna with single
port and double ports for dual polarization, Eng. Sci. Technol. Int. J. 19 (2016)
The UWB fractal antenna with slot in the ground plane has been
470–484.
successfully designed and experimentally implemented. The [18] M. Ding, R. Jin, J. Geng, Q. Wu, Design of a CPW-fed ultra wideband fractal
antenna exhibits the UWB characteristics from 3.265 GHz to antenna, Microwave Opt. Technol. Lett. 49 (2007) 173–176.
15 GHz corresponding to an impedance bandwidth of 128.497%. [19] Raj Kumar et al., On the design of inscribed triangle non-concentric circular
fractal antenna, Microwave Opt. Technol. Lett. 52 (12) (2010).
The experimental and simulated results are in good agreement. [20] Raj Kumar et al., On the design of wheel shape Fractal antenna, Microwave
The measured radiation patterns of the antenna are omnidirec- Opt. Technol. Lett. 53 (1) (2011) 155–159.
 R. Kumar, N. Kushwaha / Engineering Science and Technology, an International Journal 20 (2017) 18–27 27

[21] Raj Kumar et al., Design of CPW-fed fourth iterative UWB fractal antenna, Int. J. [26] L. Yousefi, O.M. Ramahi, Artificial magnetic materials using fractal hilbert
Microwave Opt. Technol. 6 (5) (2010). curves, IEEE Trans. Antennas Propag. 58 (8) (2010) 2614–2622.
[22] V. Crnojevíc-Bengin, V. Radoníc, B. Jokanovíc, Fractal geometries of [27] He-Xiu Xu, Guang-Ming Wang, Chen-Xin Zhang, Fractal-shaped metamaterials
complementary split-ring resonators, IEEE Trans. Microwave Theory Tech. 56 and applications toenhanced-performance devices exhibiting high selectivity,
(10) (2008) 2312–2321. Int. J. Antenna Propag. 5 (2012) 1–14.
[23] H.X. Xu, G.M. Wang, C.X. Zhang, Study and design of dual-band quarter-wave [28] E.F. Knott et al., Radar Cross Section, second ed., SciTech, Raleigh, NC, 2004.
open-circuit stub based on Kochfractal-shaped geometry of CSRRs, in: [29] D. Pozar, Radiation and scattering from a microstrip patch on a uniaxial
Proceedings of the IEEE International Conference on Microwave and substrate, IEEE Trans. Antennas Propag. 35 (6) (1987) 613–621.
Millimeter Wave Technology, 2010, pp. 1778–1780. Chengdu, China. [30] S. Hu, H. Chen, C. Law, Z. Shen, L. Zhu, W. Zhang, W. Dou, Backscattering cross
[24] H.X. Xu, G.M. Wang, Q. Peng, J.G. Liang, Novel design of tri-band filter based on section of ultra wideband antennas, IEEE Antennas Wirel. Propag. Lett. 6
fractal shaped geometry of CSSRR, Int. J. Electron. 98 (5) (2011) 647–654. (2007) 70–73.
[25] H.X. Xu, G.M. Wang, C.X. Zhang, Y. Hu, Microstrip approach benefits quad [31] G. Gui, Y. Liu, S. Gong, A novel fractal patch antenna with low RCS, J.
splitter, Microwaves RF 49 (6) (2010) 92–96. Electromagn. Waves Appl. 21 (15) (2007) 2403–2411.