Novel Coplanar Waveguide-Fed Notched Antennas With Asymmetrical Ground Plane For

Ultrawideband Applications With Band Notched Characteristic

Girish Awadhwal1, Pawan Mahicha2, P. K. Bharti, M. K. Meshram
Department of Electronics
Institute of Technology Banaras Hindu University
Varanasi, INDIA
1
girish.awadhwal.ece10@itbhu.ac.in
2
pawan.mahicha.ece10@itbhu.ac.in

Abstract—In this Paper, a coplanar waveguide (CPW) fed arbitrary interference can take place, causing the antenna nonresponsive at
shaped antenna is proposed for ultrawide band (UWB) application that frequency. It is easy to tune the notch center frequency with
which has large band-width, covering the frequency band from 2 to 12 the change in total length of the etched slot. Investigations on the
GHz. The antenna is consisting of a slotted patch, coplanar waveguide total length of the etched slot were performed by the
with two asymmetrical ground planes, and embedded inverted U
shaped slot on the radiating patch. The embedded inverted U shaped
electromagnetic software Ansoft HFSS 11. The proposed antenna
slot on the patch rejects the WLAN frequency (5.15-5.82 GHz) from yields an impedance Bandwidth of 3.1–10.6 GHz with VSWR<2,
the UWB spectrum. Parametric study of the shape parameter has except the 5–6 GHz for IEEE802.11a and HIPERLAN/2 WLAN
been carried out for the optimization of the UWB with band notched systems.
characteristics. In this paper, a compact UWB antenna area of 36.5 mm by
32.5mm is first proposed. Simply by etching slot in the radiating
Keywords— Coplanar Waveguide (CPW), Ultrawide Band (UWB), element, single band-notched characteristic from 5 to 6 GHz can be
Wireless Local Area Network (WLAN), Band Notched Characteristic easily obtained. A single band-notched characteristic for the
proposed UWB antenna can be created to reduce the potential
I. INTRODUCTION interferences between UWB system and narrowband systems.
SINCE the Federal Communications Commission (FCC) first Details of the antenna design and simulation are presented to
approved rules for the commercial use of Ultra-wide band (UWB) demonstrate the performance of the proposed antennas.
in 2002 [1], the feasible design and implementation of UWB
system has become a highly competitive topic in both academy and II. ANTENNA DESIGN
industry communities of telecommunications. In particular, as a
Fig.1 shows the geometry and configuration of a UWB
key component of the UWB system, an extremely broadband
antenna. The antenna was fabricated on h=1.6mm FR4 epoxy
antenna will be launched in the frequency range from 3.1–10.6
GHz, which has attracted significant research power in the recent substrate with dielectric constant,
εr = 4.4. As shown in the
years [2]. Challenges of the feasible UWB antenna design include
the UWB performances of the impedance matching and radiation figure, a rectangle radiator is fed by a 50 Ω coplanar waveguide
stability, the compact appearance of the antenna size, and the low (CPW) transmission line. However, unlike a conventional CPW
manufacturing cost [3]. feed topology where two equal finite ground planes are
Over the designated bandwidth of UWB system, there are symmetrically situated on each side of the central feed strip, in this
some other existing narrowband services that already occupy design, two unequal sized coplanar grounds with dimensions of
frequencies in the UWB band, such as wireless local-area network L1×Wg and L2×Wg are used and are situated on each side of the
(WLAN) IEEE802.11a and HIPERLAN/2 WLAN operating in the central feed line. The inverted-L shaped patch has two side lengths,
5–6 GHz band. To fulfill this requirement, several UWB antennas Lb and Ls, and an overall width, Wp. In addition, a notch of width
with the band-notched characteristic have been reported [4-6].In Wn and depth Ln is centrally embedded from the top edge of the
some applications, UWB antenna uses filters to suppress inverted-L patch element to improve the antenna’s matching
dispensable bands. However, the uses of filters indeed increase the condition. To examine the performance of the proposed antenna
complexity of the UWB system and lead to increase in cost. It is configurations, the commercial software Ansoft HFSS 11 is used,
desirable to design the UWB antenna with a notched frequency for required numerical analysis. Since both the antenna and the
bands in 5–6 GHz to minimize the potential interferences between feeding are implemented on the same plane, only one layer of
UWB system and narrowband systems. These UWB antennas with substrate with single-sided metallization is used, and the
filtering property at the 5–6 GHz band have been proposed not only manufacturing of the antenna is very easy and extremely low cost.
to mitigate the potential interferences but also to remove the The ground plane is beveled, which results in a smooth transition
requirement of an extra band stop filter in the system [7], [8]. This from one resonant mode to another and ensures good impedance
paper proposes a simple and compact CPW-fed planar UWB match over a broad frequency range [9], [10].
antenna with a band notched characteristics in 5.5 GHz (5–6 GHz).
The band-notched operation is achieved by etching inverted U
shaped slot in the rectangular metal radiating patch. It is found that
by adjusting the total length of the etched slot to be approximately
Quarter-wavelength of the desired notched frequency, a destructive
 0

-10

Return loss(dB)
-20

-30 7mm
7.5mm
8mm
-40

-50
2 3 4 5 6 7 8 9 10 11 12
Frequency(GHz)

Fig. 3. Simulated return loss against frequency for proposed notched

antenna with varying strip width Wf; other parameters are the same as in
Fig.1

Fig.1. Schematic diagram of the proposed CPW-fed notched antenna for Effects of variation of the small ground length L1 :
Ultra wideband operation Figure 4 Illustrates the return loss plots of the UWB antenna for
different values of small ground length L 1. It is seen clearly that the
Final antenna parameters are L=36.5mm , W=32.5mm , lower cutoff frequency dependence on this parameter. The
L1=14mm L2=29mm , Wf =7mm, g=1mm , Lb=19.5mm , Ls=6mm appropriate value of small ground length L1 is selected as 14 mm.
, Wp =28.5mm , L0=3.5mm , Ln=4.5mm, Wn=7.5mm and
t=0.39mm. Fig.2 shows the characteristics of the simulated VSWR -5

of antenna1 which is less than 2 for 2GHz to 12GHz frequency -10

Return loss(dB)
band except for 5GHz to 6GHz WLAN band . It is found that the -15

input impedance of the simulated antenna is well matched as the -20

bandwidth covers the entire UWB band (3.1–10.6 GHz). -25

13mm
-30 14mm
15mm
-35
III. R ESULTS FOR UWB CPW F EED ANTENNA
-40
A parametric study of the proposed slot antenna was carried 2 3 4 5 6 7 8
Frequency(GHz)
9 10 11 12

out in order to achieve UWB operation. To decrease the complexity

of the design, some antenna parameters are selected to be fixed as Fig.4. Simulated return loss against frequency for proposed notched
shown in Fig.1. The effects of the gap distance g, Feed line width antenna with varying small ground length L 1; other parameters are the
same as in Fig.1
Wf ,Small ground length L1,Large ground length L2,Patch left side
length Lb,Patch right side length Lb, patch width Wp,,notch length
Effects of variation of the Large ground length L2:
Ln,notch width Wn on the antenna performance will be studied in
Figure 5 Illustrates the return loss plots of the UWB antenna for
detail in this section.
different values of Large ground length L 2. It is seen clearly that
Effects of variation of the gap width g :
the frequency dependence on this parameter. The appropriate value
Figure 2 Illustrates the return loss plots of the UWB antenna for
of Large ground length L2 is selected as 29mm.
different values of gap width, g. It is seen clearly that the frequency 0
shows heavy dependence on this parameter. The appropriate value
-10
of g is selected as 1 mm.
Return loss(dB)

0
-20
-10
28.5mm
Return loss(dB)

-30
29mm
-20 29.5mm
-40
.6mm
-30 .8mm
1mm -50
1.2mm 2 3 4 5 6 7 8 9 10 11 12
-40 Frequency(GHz)

-50
2 3 4 5 6 7 8 9 10 11 12
Fig. 5. Simulated return loss against frequency for proposed notched
Frequency(GHz) antenna with varying Large ground length L2; other parameters are the
Fig. 2. Simulated return loss against frequency for proposed notched same as in Fig.1
antenna with varying gap width g .; other parameters are the same as in
Fig.1 Effects of variation of the Patch left side length Lb:
Figure 6 Illustrates the return loss plots of the UWB antenna for
Effects of variation of the strip width Wf : different values of Patch left side length L b. It is seen clearly that
Figure 3 Illustrates the return loss plots of the UWB antenna for the lower cutoff frequency dependence on this parameter. The
different values of strip width Wf. The appropriate value of Wf is appropriate value of Patch left side length Lb is selected as 19.5
selected as 7mm. mm.
 0 0

-10
-10
Return loss(dB)

-20

Return loss(dB)
-30
-20
19mm
-40 3.5mm
19.5mm
20mm 4mm
-50 -30
4.5mm
-60
2 3 4 5 6 7 8 9 10 11 12 -40
Frequency(GHz) 2 3 4 5 6 7 8 9 10 11 12
Frequency(GHz)
Fig.6 Simulated return loss against frequency for proposed notched
antenna with varying Patch left side length L b; other parameters are the
Fig.9 Simulated return loss against frequency for proposed notched
same as in Fig.1 antenna with varying notch length Ln; other parameters are the same as in
Fig.1
Effects of variation of the Patch left side length Ls:
Effects of variation of the notch Width Wn:
Figure 7 Illustrates the return loss plots of the UWB antenna for
Figure 10 Illustrates the return loss plots of the UWB antenna for
different values of Patch right side length L s. It is seen clearly that
different values of notch Width Wn. The appropriate value of notch
the lower cutoff frequency dependence on this parameter. The
Width Wn is selected as 7.5mm.
appropriate value of Patch left side length Ls is selected as 6 mm.
0
0
-10
-10
Return loss(dB)

-20

Return loss(dB)
-20

-30 6mm -30 5.5mm

6.5mm 6.5mm
7mm 7.5mm
-40 -40

-50 -50
2 3 4 5 6 7 8 9 10 11 12
Frequency(GHz)
Fig.7 -60
2 3 4 5 6 7 8 9 10 11 12
Frequency(GHz)
Simulated return loss against frequency for proposed notched antenna with
varying Patch right side length L s; other parameters are the same as in Fig.10 Simulated return loss against frequency for proposed notched
Fig.1 antenna with varying notch Width Wn; other parameters are the same as in
Fig.1
Effects of variation of the patch width Wp:
Figure 8 illustrates the return loss plots of the UWB antenna for
different values of patch width Wp . It is seen clearly that the higher Optimized Structure:
frequency dependence on this parameter. The appropriate value of Figure 11 illustrates the simulated optimized structure of coplanar
waveguide feed arbitrary shaped patch antenna. The antenna
Patch width Wp is selected as 28.5mm. characteristics show its significance in UWB applications.
-5
-5
-10

-15 -10
Return loss(dB)

-20
-15
Return loss(dB)

-25
28mm
-30 28.5mm -20
29mm
-35 -25
-40
2 3 4 5 6 7 8 9 10 11 12
Frequency(GHz) -30

Fig.8 Simulated return loss against frequency for proposed notched -35
2 3 4 5 6 7 8 9 10 11 12
antenna with varying patch width W p; other parameters are the same as in frequency(GHz)
Fig.1
Fig. 11. Simulated return loss against frequency for proposed notched
antenna for optimized parameters in Fig.1
Effects of variation of the notch length Ln:
Figure 9 Illustrates the return loss plots of the UWB antenna for IV. RESULTS FOR THE B AND NOTCHED DESIGN OF UWB
different values of notch length Ln. The appropriate value of notch CPW – F ED SLOT ANTENNA
length Ln is selected as 4.5mm. To achieve band-notched characteristics, Inverted U shaped
slot is etched on an UWB antenna patch. The etched slot is
intended to resonate at certain frequency at which the antenna is
designed to exhibit band-notched characteristics. Details of the
design to generate single-notched band with central frequency of
5.5 GHz will be studied in this section.
EFFECT OF SLOT LENGTH (L0) TO GENERATE NOTCHED BAND IN [10] W. Wang and S. S. Zhong, “A broadband CPW-fed arrow like printed
WLAN (5.5 GHz): antenna,” in Proc. IEEE AP-S Int. Symp., Jun. 2004, vol. 1, pp.751–754.
As the total length of inverted U shaped slot is 17.39mm, which has
two equal side arms of length L0, that varies from 3.3mm to 3.7mm
due to which the centre frequency of the notched band varies. It can
be seen that the bandwidth of the notch remains almost fixed and
the effect of the notch on VSWR varies between 5 and 6. From this
result, one can conclude that the intensity and frequency of the
notched band is controllable by changing the length L 0.As the
length L0 increases from 3.3mm to 3.7 mm, the centre frequency of
the notched band varies from 5.6GHz to5.3 GHz. It can be seen
that the bandwidth of the notch remains almost fixed and the effect
of the notch on VSWR varies between 5and 6.
7
3.3mm
6 3.5mm
3.7mm
Return loss(dB)

1
2 3 4 5 6 7 8 9 10 11 12
Frequency(GHz)

Fig.12 Simulated VSWR against frequency for proposed notched antenna

for varying inverted U shaped slot length L0 other parameters are the
same as in Fig.1

V. CONCLUSION
A new single-layer antenna topology based on the CPW-fed
Antenna for a Ultra-wideband operation has been presented. With
the use of asymmetrical ground planes for the CPW-fed
structure,the proposed antenna has Ultra-wideband characteristic.
The effects of varying slot length in the patch a WLAN frequency
band rejection property have also been examined.

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