A Microstrip fed antenna which consists of a rectangular patch with rectangular shaped slot incorporated into patch is presented for ultra wide band application with enhanced bandwidth. The proposed antenna achieves an impedance bandwidth of 8.9GHz (2.3-11.2GHz) with VSWR< 2 for over the entire bandwidth.

1. International Journal of Electrical & Electronics Engineering 4 www.ijeee-apm.com
IJEEE, Vol. 1, Issue 3 (2014) e-ISSN: 1694-2310 | p-ISSN: 1694-2426
DESIGN & PARAMETRIC STUDY OF
RECTANGULAR SLOT MICROSTRIP PATCH
ANTENNA FOR UWB APPLICATIONS
1
Arvind Yadav, 2
Dr. Kuldip Pahwa
1
M.tech Student, Department of E.C.E, M.M.U. Mullana, Ambala, Haryana, India
2
Professor, Department of E.C.E, M.M.U Mullana, Ambala, Haryana, India
1
arvinnd0519@gmail.com, 2
kpahwa2002@gmail.com
Abstract- A Microstrip fed antenna which consists of a
rectangular patch with rectangular shaped slot incorporated
into patch is presented for ultra wide band application with
enhanced bandwidth. The proposed antenna achieves an
impedance bandwidth of 8.9GHz (2.3-11.2GHz) with
VSWR< 2 for over the entire bandwidth. Good return loss and
radiation pattern characteristics are obtained in the frequency
band of interest. The proposed antenna is designed on low
cost FR-4 substrate fed by a 50-Ω microstrip line. The
simulation was performed in High Frequency Structure
Simulator Software (HFSS). The antenna parameters such as
resonant frequency, return loss, radiation pattern and VSWR
are simulated and discussed in this paper.
The several factors affecting the bandwidth of the microstrip
antenna such as the thickness of the substrate, the dielectric
constant of the substrate and the shape of the patch also
studied in this paper.
Index Terms — Enhanced Bandwidth, Ultra wideband (UWB)
VSWR, HFSS.
I. INTRODUCTION
The accelerating growth of ultra-wideband (UWB) technology
calls for efficient communication devices. Antennas, as an
important part of every communication system, are required to
offer characteristics such as compact size, light weight, easy
fabrication process, omni-directional radiation properties, and
wide bandwidth to be worthy of being used in UWB
systems[1]. The Federal Communication Commission (FCC)
allocation the unlicensed use of band from 3.1 to 10.6 GHz
widely known as UWB technology and opens it for
commercial applications for short range indoor and outdoor
wireless communication [2].The UWB antenna is an
significant component of UWB communication system and
has drawn growing attention [3-5]. It is well known fact that
microstrip patch antennas offers many advantages such as low
profile, light weight, ease of fabrication and compatibility
with printed circuits. However, the serious problem of patch
antennas is their narrow bandwidth. To overcome their
inherent limitations of narrow impedance bandwidth many
techniques have been proposed and investigated, for example,
slotted patch antennas [6 - 8], microstrip patch antennas on
electrically thick substrate, gap coupled patches, the use of
various impedance matching and feeding techniques [9-10].
However, simultaneously bandwidth enhancement and size
reduction are becoming major design considerations for
practical applications of microstrip antennas as improvement
of one of the characteristics, normally results in degradation
of the other, researchers have encountered that there is
generally a tradeoff between size of antenna and wideband
characteristics of antenna. In recent years, many techniques
have been reported to achieve wideband patch antenna for
modern wireless communication devices [11].
II. ANTENNA STRUCTURE AND DESIGN
The three essential parameters for the design of a rectangular
microstrip patch antenna are:
Frequency of operation ( 0f ): The resonant frequency of the
antenna must be selected appropriately. The resonant
frequency selected for design is 7.5 GHz.
Dielectric constant of the substrate ( r ): The dielectric
material selected for the design is FR4-epoxy which has a
dielectric constant of 4.4. A substrate with a high dielectric
constant reduces the dimensions of the antenna.
Height of dielectric substrate (h): For the microstrip patch
antenna it is essential that the antenna is not bulky. Hence, the
height of the dielectric substrate is selected as 1.5mm.
The design parameters that are assumed and evaluated are
shown in Fig.1 as below:
Fig. 1 Side View of Antenna
Step 1: Calculation of the Width (W): The width of the
Microstrip patch antenna is given by [12] following equation:
W =
c
2f
ε +1
2
(1)

2. www.ijeee-apm.com International Journal of Electrical & Electronics Engineering 5
Substituting εr=4.4, c=3x108
m/sec, fo= 7.5GHz gives:
W=12mm
Step 2: Calculation of Effective Dielectric Constant (εreff): The
following equation gives the effective dielectric constant as
[12]:
ε =
ε + 1
2
+
ε − 1
2
1 + 12
h
W
(2)
Substituting εr=4.4, W=12mm, h=1.5mm gives: εreff =3.7
Step 3: Calculation of Effective Length ( effL ): The effective
length is given [12]as:
L =
c
2f ε
(3)
Substituting: fo=7.5GHz, c=3x108
m/sec, εreff =3.7 gives: Leff
=10.2mm
Step 4: Calculation of the Length Extension (ΔL): Equation
below gives the length extension [12] as:
∆
= 0.412
(ε . ) .
(ε . ) .
(4)
Substituting the values, the length extension (ΔL) is obtained
as: ΔL=.6mm
Step 5: Calculation of Actual Length of Patch (L): The actual
length of the antenna can be calculated [12] as:
L = L − 2 × ∆L (5)
Substituting Leff =10.2mm and ∆L=0.6mm the actual length
come out to be: L=9mm
III. PARAMETERS OF RECTANGULAR SLOT
ANTENNA
In this section parameters of a rectangular slot antenna has
been discussed which is printed on a dielectric substrate of
FR4 with relative permittivity (εr) of 4.4. The fig 2 shows the
patch with finite ground plane. The length of ground plane Lg
is determined using parametric analysis and its optimum value
is found to be 7.5mm.
Fig 2 Dimension of Rectangular Slot Patch Antenna
Table 1 Parameters of Rectangular Slot Patch Antenna
The length Lg has a very important role in controlling the
coupling between ground plane and patch. This coupling
causes to spread of the impedance bandwidth and hence must
be accurately measured. The various parameters of the patch
antenna which includes shape of the patch , dielectric used,
length and width of the patch ,thickness of patch and length
and width of the slot as shown in table 1.
IV. RESULT AND DISCUSSION OF RECTANGULAR
SLOT PATCH ANTENNA
The return loss, VSWR and gain of the proposed antenna is
shown in Fig 3 (a, b, c) respectively. The discussed design
achieves the return loss of -17.67dB and the bandwidth of 8.9
GHz (2.3- 11.2GHz) and corresponding VSWR is < 2 for
entire bandwidth range. Simulated results show that the
proposed antenna could be a good candidate for UWB
applications.
Fig 3(a) Return Loss
PARAMETERS DIMENSIONS
Substrate Length 21mm
Substrate breadth 18mm
Substrate thickness 1.5mm
Dielectric constant of substrate 4.4
Tangent loss 0.02
Patch length 9mm
Patch breadth 12mm
Input resistance of the Patch (Rin) 50 Ω
Length of slot (L1) 5mm
Width of slot (w1) 8mm
Top View Bottom View

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Fig 3(b) VSWR
Fig 3(c) 3- D Polar Plot
V. PARAMETRIC STUDY OF RECTANGULAR SLOT
WIDEBAND MICROSTRIP ANTENNA
(a)Effect of variation in substrate thickness on the bandwidth
of the antenna
Table 2 Comparison of Different Substrate Thicknesses
It is known that the easiest way to increase the bandwidth of a
microstrip antenna is to print the antenna on a thicker
substrate. Fig 4(a) and table 2 show that as the thickness of the
substrate increases the bandwidth increases and as the
thickness of the substrate decreases the bandwidth decreases.
Fig 4(a) Effect of the Substrate Height on the Bandwidth of the
Antenna
However, thick substrates tend to trap surface wave modes,
especially if the dielectric constant of the substrate is high. In
addition, longer coaxial probe feeds will experience high
inductive feed effects. Finally, if the substrate is very thick,
radiating modes higher than the fundamental will be excited
[13]. All of these effects degrade the primary radiator, cause
pattern distortion, and detune the input impedance of the
microstrip antenna.
(b) Effect of variation in dielectric constant on the bandwidth
of the antenna
Fig 4(b) Effect of the Dielectric Constant on the Bandwidth of the
Antenna
SUBSTRATE
THICKNESS
(mm)
DIELECTRIC
CONSTANT
(ε r)
OPERATING
BAND
(GHz)
BANDWIDTH
(GHz)
1.5 4.4 2.3-11.2 8.9
1.2 4.4 2.8-10.7 7.9
1.7 4.4 2.0-12.8 10.8

4. www.ijeee-apm.com International Journal of Electrical & Electronics Engineering 7
Table 3 Comparison of Different Substrate Materials
As it can be analyzed from the fig 4(b) and table 3 which
shows that as the dielectric constant decreases than bandwidth
increases and as the dielectric constant increases than
bandwidth decreases. However, this has detrimental effects on
antenna size reduction since the resonant length of a
microstrip antenna is shorter for higher substrate dielectric
constant. In addition, this antenna can easily be used in other
frequency bands with different substrate materials [13].
(c) Effect of variation in slot length and width on the
bandwidth of the antenna
Fig 4(c) Effect of The Variation in Slot Length And Width on The
Bandwidth of The Antenna
Table 4 Comparison f Different Slot Length and Width
It can be seen from the fig (c) and table 4, which shows that
the variation of slot length L1 and slot width W1 effect
bandwidth and return loss of the antenna. When L1 and W1 is
(4*9) then bandwidth is increases but return loss is very less
and when L1 and W1 is (6*9) then both bandwidth and return
loss is decreases as compared with (5*8) slot length and
width.
V. CONCLUSION
This paper has proposed a simple design of patch antenna
having a UWB range for communication. In the design a slot
is incorporated into the rectangular patch to expand its
bandwidth and to reduce the size of antenna .The designed
antenna is very simple in look and small in size . Simulation
results show that the antenna has VSWR < 2 from 2.3- 11.2
GHz and bandwidth of antenna is 8.9GHz .The antenna
parameters such as return loss, VSWR, impedance bandwidth,
gain have been studied. Simulated results of antenna show
that the proposed antenna could be a good candidate for UWB
application. The effects of the substrate thickness, the
dielectric constant of the substrate and variation in slot
position on the bandwidth have been studied. It has been
found that, in order to obtain a wideband microstrip patch
antenna with good efficiency, a thick substrate with a very
low dielectric constant should be used. It has also been shown
that these antennas can easily be used in other frequency
bands with different substrate materials.
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DIELECTRIC
CONSTANT
(ε r)
SUBSTRATE
THICKNESS
(mm)
OPERATING
BAND
(GHz)
BANDWIDTH
(GHz)
4.4 1.5 2.3-11.2 8.9
3.8 1.5 2.2-11.6 9.4
4.8 1.5 2.4-10.5 8.1
SLOT LENGTH
& WIDTH
(L 1 & W 1)
DIELECTRIC
CONSTANT
(ε r)
OPERATING
BAND
(GHz)
BANDWIDTH
(GHz)
L 1 = 5 & W 1 = 8 4.4 2.3-11.2 8.9
L 1 = 4& W 1 = 9 4.4 2.2-11.7 9.5
L 1 = 6 & W 1 =7 4.4 2.4-10.8 8.4

5. International Journal of Electrical & Electronics Engineering 8 www.ijeee-apm.com
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