Enhanced bandwidth slotted microstrip patch antenna

INTERNATIONAL JOURNAL OF ELECTRONICS AND
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 4, Issue 2, March – April, 2013, pp. 41-47
IJECET
© IAEME: www.iaeme.com/ijecet.asp
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ENHANCED BANDWIDTH SLOTTED MICROSTRIP PATCH
ANTENNA

Anurag Sharma*, Ramesh Bharti**, ArchanaAgarwal***
*M-Tech Student, Jagannath University, Jaipur
**Assistant Professor, Jagannath University, Jaipur
***Assistant Professor, Institute of Technology and Management, Bhilwara

ABSTRACT

In this paper, in order to improve the performance of a conventional microstrip patch
antenna a new design technique for enhancing the bandwidth of antenna is proposed. This
paper includes a wideband inverted slotted microstrip patch antenna fed by microstrip
transmission line feed. The design enumerates contemporary techniques such as microstrip
transmission line feeding, inverted patch structure and slotted patch. The combined effect of
integrating these techniques and by introducing the proposed design, offer a low profile,
enhanced bandwidth, and high gain. The antenna operating the band of 1-12 GHz shows an
impedance bandwidth (2:1 VSWR) of UWB.

Keywords: Slotted antenna, Microstrip patch antenna, wideband, Microstrip Transmission
Line fed.

I. INTRODUCTION

As the process of miniaturization of devices is in full swing, antennas cannot remain
as standalone devices. Compact designs have to be implemented to cope with the demands of
the industry. With the explosive growth of wireless system and booming demand for a variety
of new wireless application, there is great need to design broadband antennas to cover a wide
frequency range. Now days the designers are basically focused to deal with UWB (Ultra
Wide Band) Technology and to make advance antennas that can give UWB response so that
they can be operated in that particular frequency range. With increasing requirements for
personal and mobile communications, the demand for smaller and low-profile antennas has

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brought the microstrip antennas to forefront. Modifying the shape and dimensions of
conventional microstrip antennas leads to the design of microstrip antenna for UWB
communication system by tuning the shape and dimensions. Present time is witnessing a very
rapid growth of wireless communications, for which antennas with very large bandwidth are
in strong demand. Microstrip antennas are attractive due to their light weight, conformability
and low cost and have broad application in wireless communication system owing to their
advantages such as low-profile, conformability, low-cost fabrication and ease of integration
with feed-networks [7]. For good antenna performance, a thick dielectric substrate having a
low dielectric constant is desirable since this provides better efficiency, larger bandwidth and
better radiation. However, such a configuration leads to a larger antenna size. In order to
design a compact Microstrip patch antenna, substrates with higher dielectric constants must
be used which are less efficient and result in narrower bandwidth. Hence a trade-off must be
realized between the antenna dimensions and antenna performance. There are various
methods to increase the bandwidth of antennas, including increase of the substrate thickness,
the use of a low dielectric substrate, the use of various impedance matching and feeding
techniques, the use of multiple resonators, and the use of slot antenna geometry[2],[5],[6].
In order to enhance the bandwidth, several techniques have been proposed. A novel
single layer wide-band rectangular patch antenna with achievable impedance bandwidth of
greater than 20% has been demonstrated [3]. Utilizing the shorting pins or shorting walls on
the unequal arms of a U-shaped patch, U-slot patch, or L-probe feed patch antennas,
wideband and dual-band impedance bandwidth have been achieved with electrically small
size [4],[9],[10]. In this paper, for enhancing the impedance bandwidth, a novel slotted
double E shape patch is proposed. A better cross-polarization and wider impedance
bandwidth of 28% is achieved compared to the design reported in [11].

II. ULTRA-WIDE BAND TECHNOLOGY

UWB or Ultra-Wide Band technology offers many advantages, especially in terms of
very high data transmission rates which are well beyond those possible with currently
deployed technologies such as 802.11a, b, g, WiMax and the like. As such UWB, ultra
wideband technology is gaining considerable acceptance and being proposed for use in a
number of areas. Already Bluetooth, Wireless USB and others are developing solutions, and
in these areas alone its use should be colossal.
Just as many wireless technologies seem to be moving into high volume production
and becoming established a new technology has hit the scene and is threatening to turn the
industry upside down. Known as Ultra Wide Band (UWB) this new technology has much to
offer both in the performance and data rates as well as the wide number of application in
which it can be used. Currently ultra wideband (UWB) technology has been proposed for or
is being used in applications from radar and sensing applications right through to high band
width communications. Furthermore ultra wide band, UWB can be used in both commercial
and military applications.
There are a wide number of applications that UWB technology can be used for. They
range from data and voice communications through to radar and tagging. With the growing
number of way in which wireless technology can be used, the list is likely to grow. Due to the
extremely low emission levels currently allowed by regulatory agencies, UWB systems tend
to be short-range and indoors. However, due to the short duration of the UWB pulses, it is
easier to engineer extremely high data rates.

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Fig 1. Comparison of Narrowband, Spread Spectrum and Ultra wide band Signal Concept

With the growing level of wireless communications, ultra wide band UWB offers
significant advantages in many areas. One of the main attractions for WAN / LAN
applications is the very high data rates that can be supported. With computer technology
requiring ever increasing amounts of data to be transported, it is likely that standards such as
802.11 and others may not be able to support the data speeds required in some applications. It
is in overcoming this problem where UWB may well become a major technology of the
future.

Fig 2. Features and benefits of UWB

III. DESIGN PROCEDURE

The basic design steps includes following parameters Frequency of operation: The
resonant frequency must be selected appropriately. For my design the frequency selected will
be from ultra wideband frequency range.
Dielectric constant of the substrate εr: The Dielectric constant of the substrate plays an
important role in patch antenna design. A substrate with high dielectric constant reduces the
dimensions of antenna but it also affects the antenna performance. So, there is a trade-off
between size and dimensions of antenna.
Height of Dielectric substrate: For the Micro strip patch antenna to be used in communication
system, it is essential that the antenna is not bulky. Hence the height of dielectric should be
less.

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IV. ANTENNA DESIGN LAYOUT

Fig. 3 depicts the geometry of the proposed patch antenna. The inverted rectangular
patch, with width W and length L is supported by a low dielectric superstrate with dielectric
permittivity εl and thickness hl. An air-filled substrate with dielectric permittivity εo and
thickness ho is sandwiched between the superstrate and a ground plane. The proposed patch
integrates the double E shaped patch on the same radiating element. For the main E-shaped,
the slots are embedded in parallel on the radiating edge of the patch symmetrically with
respect to the centerline (x-axis) of the patch and it is incorporated extra E shaped slot on the
same radiating edge of opposite side. The patch is fed by a coaxial probe along the centerline
(x-axis) at a distance H from the edge of the patch as shown in Fig. 1(b). Table I shows the
optimized design parameters obtained for the proposed patch antenna. A dielectric substrate
with dielectric permittivity, εl of 2.2 and thickness, hl of 1.5748mm has been used in this
research. The thickness of the air-filled substrate ho is 12.5mm. An Aluminum plate with
dimensions of 1.393 λ0 ×1.254 λ0 (where λ0 is the guided wavelength of the centre operating
frequency) and thickness of 1 mm is used as the ground plane. The proposed antenna is
designed to operate at 1.80 GHz to 2.36 GHz region.
This design employs contemporary techniques namely, the microstrip transmission
line feeding, inverted patch, and slotted patch techniques to meet the design requirement. The
use of transmission line feeding technique with a thick air-filled substrate provides the
bandwidth enhancement, while the application of superstrate with inverted radiating patch
offers a gain enhancement, and the use of parallel slots also reduce the size of the patch. The
use of superstrate on the other hand would also provide the necessary protections for the
patch from the environmental effects. By incorporating extra E shape slots in radiating edges,
the gain and cross-polarization has been improved. These techniques offer easy patch
fabrications, especially for array structures.

Fig 3. Geometry of proposed patch antenna

Dimension W L w0 l0 h0 H
mm 75 46 7 30 12.5 12
Dimension w1 l1 hl Wf Lf Gpf
mm 15 5 1.5748 6.2 35.1 1
Table 1 Proposed Patch antenna design parameters in millimeters (mm)

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V. SIMULATION RESULTS

CST Microwave Studio has been used to calculate return loss, impedance bandwidth,
radiation pattern and gains. Fig. 4 and Fig.6 depicts the simulated result of the return loss and
group delay of the proposed antenna. From the figure, the simulated group delay shows less
variation on broader bandwidth except for sharp changes at the middle of the center
frequency at 6.85 GHz.
The simulated impedance bandwidth of 5 GHz is achieved at 10 dB return loss
(VSWR≤2).

Fig 4: Return Loss Curve of the proposed patch antenna

Antenna radiation pattern depicts the radiation properties on antenna as a function of
space coordinate. For a linearly polarized antenna, performance of antenna is often described
in terms of the E and H plane patterns [12]. The H-plane is defined as the plane containing
the magnetic field vector and the direction of maximum radiation [13] while E-plane as the
plane containing the electric field vector and the directions of maximum radiation while Fig.5
shows the simulated two dimensional E and H-plane at upper bound frequency. In the E-
plane, the value of azimuth angle of 0o, 45o and 90o while in H-plane, the value of
o o o
elevation angle θ of 0 , 45 and 90 are taken into consideration.

Fig 5: Radiation pattern curve of the proposed patch antenna

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Fig 6: Group delay of the optimized proposed antenna.

VI. CONCLUSION

For enhancing bandwidth of microstrip a new double E shaped patch antenna is
successfully designed in this paper. An impedance bandwidth of 5 Ghz is achieved in this
design with respect to the centre frequency of 6.85 GHz by employing proposed slotted patch
shaped design, inverted patch, and microstrip transmission line feeding techniques. With this,
good radiation characteristics and antenna gain have also been obtained. The proposed patch
has a simple structure with dimension of 0.516 λ0× 0.383 λ0. The design is suitable for array
applications with respect to a given frequency of 1-12 GHz.

REFERENCES

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Enhanced bandwidth slotted microstrip patch antenna

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