Bandwidth Optimization of Microstrip Patch Antenna-A Basic Overview
Bandwidth Optimization of Microstrip Patch Antenna-A Basic Overview
Bandwidth Optimization of Microstrip Patch Antenna-A Basic Overview
Abstract — An antenna is a very important device in wireless applications. It converts the electrical energy into RF signal at the transmitter and
RF signal into electrical energy at the receiver side. A micro strip antenna consists of a rectangular patch on a ground plane separated by
dielectric substrate. The patch in the antenna is made of a conducting material Cu (Copper) or Au (Gold) and this can be in any shape of
rectangular, circular, triangular, elliptical or some other common shape. Researches of past few year shows that, various work on Microstrip
Patch Antenna is attentive on designing compact sized Microstrip Antenna with efficiency and bandwidth optimized. But inherently Microstrip
Patch Antenna have narrow bandwidth so to enhance bandwidth various techniques are engaged. Today‘s Communication devices need several
applications which require higher bandwidth; such as mobile phones these days are getting thinner and smarter but many applications supported
by them require higher bandwidth, so microstrip antenna used for performing this operation should provide wider bandwidth as well as their
shape should be more efficient and size should be compact so that it should occupy less space while keeping the size of device as small as
possible. In this review paper, a review of different techniques used for bandwidth optimization & various shapes of compact and broadband
microstrip patch antenna is given.
Keywords— Microwave Communication; Microstrip Antenna; Antenna Designing; Bandwidth Optimization; Rectangular shape Patch Antenna.
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Where,
(2)
Figure 1 Micro strip Patch Antenna [2] II. MICROSTRIP PATCH ANTENNA
Micro strip antenna has a number of advantages which are Antennas are based on transmission or reception of
small size, low profile, low weight but have a number of electromagnetic waves. Microstrip antennas have several
disadvantages like low bandwidth, low gain. Hence instead advantages over conventional microwave antenna and
of improving this, fractal geometry has been applied on
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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therefore are used in a variety of practical applications.
Microstrip antenna in its simplest design is shown in Figure
2. It consists of a radiating patch on one side of dielectric
substrate (Єr≤10), with a ground plane on other side.
A microstrip patch antenna (MPA) consists of a
conducting (metallic patch on a thin, grounded dielectric
substrate) patch of any non-planar or planar geometry on
one side of a dielectric substrate and a ground plane on other
side. It is a printed resonant antenna for narrow-band
microwave wireless links requiring semi-hemispherical
coverage.
A. Taper Matching
Figure 2 Microstrip antenna with substrate and ground A patch antenna operating at 5GHz was designed using the
conventional design equations available in it. In the 1 st
Due to its planar configuration and ease of integration with design (antenna a) we used a quarter wavelength long
microstrip technology, the microstrip patch antenna has rectangular microstrip transmission line (TL) for impedance
been widely utilized. The rectangular and circular patches matching. The antenna substrate was RT/Duroid 5880 with
are the basic and most commonly used microstrip antennas. , h=3.175 mm and t=0.035 mm so that we can get
The characteristic impedance of the microstrip line is large antenna‘s dimensions (see Fig.5), high gain and high
determined by the substrate thickness, strip, width and bandwidth.
dielectric constant.
=7mm which gives the widest and deepest response V. BACKGROUND & OVERVIEW
around 5GHz.
According to [3] the substrate material plays significant role
IV. ADVANTAGES AND DISADVANTAGES OF determining the size and bandwidth of an antenna.
MICROSTRIP PATCH ANTENNAS Increasing the dielectric constant decreases the size but
lowers the bandwidth and efficiency of the antenna while
Microstrip patch antennas are increasing in popularity for decreasing the dielectric constant increases the bandwidth
use in wireless applications due to their low-profile but with an increase in size. Some research papers reviews
structure. Therefore they are extremely compatible for are mentioned below.
embedded antennas in handheld wireless devices such as In [4] antenna is feed using microstrip feeding technique and
cellular phones, pagers etc. The telemetry and simulated using IE3D software The antenna shows single
communication antennas on missiles need to be thin and band bandwidth of 2 GHz for the working band of 4-6 GHz.
conformal and are often in the form of microstrip patch The proposed antenna is useful for IEEE 802.11 WLAN
antennas. Another area where they have been used standards in the 5.2/5.8 GHz band and WiMAX standards in
the 5.5 GHz band. In [5] defected ground plane is in the
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IJRITCC | February 2018, Available @ http://www.ijritcc.org
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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form of L shaped slot and the rectangular parasitic patches for WiMax, 5.2 GHz and 5.8 GHz for WLAN and 6-7 GHz
and diagonal cuts at top corners can increase the bandwidth. for satellite application respectively.
For the first and second resonant frequencies Return losses
of −17dB and −30 dB respectively, can be achieved when A. Edge tapered wideband rectangular patch antenna
the diagonal cut is at optimum value. [13] proposed an edge tapered wideband
In [6] a rectangular microstrip patch antenna with rectangular patch antenna with one slot at the center and
DGS has been simulated using High Frequency Simulation parasitic stubs on two sides of the patch. In this paper partial
Software (HFSS) at 2.45 GHz frequency, antenna is fed by ground is used. The height of the ground is varied from
Quarter Transformer feeding. The rectangular patch antenna 8.6mm to 9.2mm and their effect on return loss was
designed with swastik shaped DGS structure, shows gain of measured. Also the effect of varying the length of parasitic
7 dB. Patch antenna with Defected Ground Structure (DGS) stub was measured.
demonstrate properties like improved returning loss, VSWR,
bandwidth, gain of the antenna as compared to the
conventional antenna.
In [7] a single frequency microstrip patch antenna
feed using microstrip line fed and simulated using CST
Microwave Studio software. Antenna operates at the
frequency 5.2 GHz WLAN standard. Resultant impedance
bandwidth is around 190 MHz with the having value of
return loss as -47 dB has been obtained. The antenna also
shows impedance of 50.89 ohm. In [8] circular patch
antenna is designed with defect in ground plane.
In [9] antenna operating at 2.4 GHz frequency band
Figure 6 2D View of Proposed Antenna with Slot and
for WLAN applications uses rectangular slot in the ground
Parasitic Stub [14]
plane is located at different locations in the bottom of the
substrate are considered and results of optimized patch Length was varied from 4 to 8 mm. This antenna was
antenna were obtained. Return loss improvement is from - designed for wideband applications having bandwidth of
17.72dB to -26.92dB. Gain improvement is from-5.1dB to - 112%. This antenna also has good radiation pattern with a
5.9 dB. gain of 2.65dB and having 83.9% radiation efficiency. The
In [3] antenna Simulated at 4.30 GHz frequency overall dimension of the antenna is 35 × 35 × 1.6 mm3.
and it is proved that when defect is introduced in ground
plane of the single band antenna then the resulting antenna B. G- Shape Patch Antenna
has its resonant frequency at lower side that is at 2.5GHz, [15] proposed a circularly proposed dual
which shows that the antenna has compact in size and
band single layer G-Shaped patch antenna with using HFSS.
showing improvement in gain and bandwidth. Here
By using four slots on patch antenna he designed a G shape
multiband operation of antenna is also obtained.
on patch. Micro strip antenna has limited bandwidth due to
In [10] very compact antenna was designed, the
resonance behavior. To increase the radiation and
antenna for WLAN operating in band of 2.4 and 5GHz.
bandwidth, shape of patch can be changed by creating slots
Various results are obtained by varying different dimensions
on it. The main idea behind this is to provide two resonance
of patch. Antenna is feed using microstripfeed. Different
frequencies. These frequencies are 3 GHz and 3.8 GHz. At 3
defected ground structures (DGS) have been developed
GHz frequency achieved gain and return loss are 7.5 dB and
analyzed.
-17 dB and at 3.8 GHz gain and return loss are 2.4 dB and -
In [11] and it is concluded that although the DGS has
15 dB.
applications in the field of the, microwave oscillators,
microwave filter design, microwave couplers to increase the
coupling, microwave amplifiers, etc., it can be used in the
microstrip antenna design for various advantages such as
antenna size reduction mutual coupling reduction, harmonic
suppression, cross polarization reduction, in antenna arrays
etc. In [12] microstrip patch antenna for GSM and Wi-Max
application was proposed. The proposed antenna shows
promising characteristics at resonant frequencies of 5.5 GHz
Figure 7 Design of G- Shape Patch Antenna in HFSS [14]
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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C. Micro strip -fed ultra-wideband (UWB) planar monopole observed that by increasing the indentation factor in the
antenna fractal section of the radiator, the resonance frequencies of
[16] proposed a novel modified micro the antenna changes and by suitably choosing this value one
can get an antenna design with improved bandwidth with
strip -fed ultra-wideband (UWB) planar monopole antenna
good gain at both the resonance frequencies.
with variable frequency band-notch function. In this design
bandwidth magnification can be done by putting two slots in
the both sides of micro strip feed line on the ground plane.
This antenna is constructed using FR4 substrate with
thickness of 1.0 mm with dielectric constant of 4.4. The
additional current path can be provided by cutting slots and
this also change the inductance and conductance of input
impedance which changes the bandwidth. A modified H-
shaped conductor-backed plane with variable dimensions is
used in order to generate the frequency band-stop
performance and control its characteristics such as band-
notch frequency and its bandwidth. By changing the shape Figure 9 (a) Antenna with 1st iteration fractal. (b) Antenna
and size of slot, the resonant character of structure with 2nd iteration fractal [16]
transmission with resonant frequency can be controlled. The
E. Wideband fractal shaped slot antennas
designed antenna has a small size of 22×22mm2 and
operates over the frequency band between 3.1 and 13.9 GHz [18] proposed a wideband fractal shaped
for VSWR <2 with band rejection performance in the slot antennas for X- band application. A novel fractal
frequency band of 5.1 to 5.9 GHz. patterned iris loaded cross dipole slot antenna along broad
wall of rectangular waveguide at X- band is designed. To
improve the impedance matching, the method of junction
tapering of the cross slots is used. Bandwidth improvement
is t better than 2 GHz with optimization of iris depth and
inclusion of a second iteration slot in the vicinity of the
primary cross slot. Peak realized gain remains around 7 dB
over the operational bandwidth.
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IJRITCC | February 2018, Available @ http://www.ijritcc.org
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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TABLE 1 Table for the Comparative Analysis of Different Techniques
Sr. Title Technique Input parameter Output parameter
No
1. An Edge Tapered A rectangular patch FR4 Epoxy Glass was used as Percentage Bandwidth =
Rectangular Patch antenna with tapered substrate with thickness of 1.6 112% (centered at 6.01
Antenna with Parasitic edge was designed. The mm GHz)
Stubs and Slot for slot and parasitic stubs Dielectric constant of substrate= Average radiation
Wideband Applications were also used for this 4.4 Antenna size=35 × 35 ×1.6 efficiency= 83.9%
[14] design. mm3.
2. Single Layer DualBand A G- shape slot was cut Dielectric constant =2.2 At frequency 3 GHz
G-shaped patch on the patch for Substrate thickness =4mm BW= 500 MHz
antenna [13] bandwidth magnification. Patch length (L) =30mm Gain = 7.5 dBi
Patch width(W) =40mm Return loss= -17 dBi
At frequency 3.8 GHz
BW= 400 MHz
Gain= 2.4 dBi
Return loss= -15dBi
3. Novel Modified UWB In this paper H- shape Ground-22×22 mm2 Patch (VSWR<2) for
Planar Monopole was designed on patch length-13.5mm frequency band of 3.1
Antenna with Variable antenna and also two Patch width -10mm to over 13.9 GHz
Frequency Band-Notch square slots are inserted feed line length-8mm with rejection band
Function [15] on ground plane. This Feed line width- 1.86mm around 5.1 to 6 GHz.
DGS provide an
additional current path.
5. Wideband fractal Fractal geometry was At 1st iteration length and width Bandwidth magnification
shaped slot antenna for used. A second iteration of + sign was 15mm and 2mm. better than 2 GHz and 2
X-band application fractal shaped cross slot At 2nd iteration length and width GHz 3 dB pattern
[17] is fabricated along the of + sign was 5.4mm and 72mm. bandwidth was obtained.
centre of the broadwall
of a rectangular
waveguide.
6. Micro strip E shape antenna was Resonant frequency fr 3.1GHz Gain = 4.7 dB
Symmetrical E-Shape designed by cutting two co-axial feed line was used. Return loss = -28 dB
Patch Antenna for the slots from rectangular Ground plane-41×31 mm2 Patch-
Wireless patch. 31×21 mm2
Communication
Systems [19]
A pattern and impedance bandwidth better than 2 GHz (9.6 [19] represent a design & analysis of E-
to 12 GHz) is calculated with a second iteration cross dipole shape micro strip patch antenna for wireless communication.
fractal shape centered slot antenna loaded with a curved The benefits of this antenna were decrease in volume, low
partial height iris of 4 mm thickness and 7.2 mm depth [18]. profile configuration, smoothly mounted, light weight, less
production cost. The antenna operates on 3.1GHz and
F. E-shape micro strip patch antenna
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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3.45GHz frequencies. This antenna was implemented by Conventional U slot patch antenna, parametric analysis is
using FR4 substrate with dielectric constant 4.2 and analysed. Also effect of U slot inclusion on performance of
thickness of 1.6mm. To enhance the bandwidth two parallel patch antenna was analysed.
Antenna was designed and simulated using HFSS
slots were cut which provide additional current path. To
simulated software and good effects were obtained between
achieve the desired output parameters, the dimensions of practical and experimental results. The antenna operating
patch and ground can also be changed [20]. It has been frequency range is 5.18–5.8 GHz with VSWR less than 2,
detected that the position of feed points effects the behavior which corresponds to 11.8% impedance bandwidth. It
of the designed antenna. The return loss of -12dB of and - exhibits two radiation beams, directed at 35 and with 7.92
28dB at operating frequencies 3.1GHz and 3.45GHz dBi and 5.94 dBi realized gain, respectively at 5.5 GHz.
respectively were calculated using this design. To simulate
H. Circular symmetric slotted microstrip patch antenna
the results of designed antenna HFSS software was used.
[22] proposed circular symmetric slotted
microstrip patch antenna with compact size. This antenna
was obtained by cutting shapes in diagonal directions of
microstrip patch antenna. . A measured 3 dB axial-ratio
(AR) bandwidth of around 0.7% (6.0 MHz) with 2.0% (18.0
MHz) impedance bandwidth was achieved.
The measured boresight gain was more than 3.3
dBi over the operating band was obtained. Different shapes
for the slots are studied and compared, based on the fixed
overall volume of the antenna for circularly polarized
diagonally symmetric slotted microstrip-patch antennas.
This antenna was designed to have compact size of small
Figure 11 Design of Proposed Antenna (Top View) [18] dimensions.
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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TABLE 2 Table for the Comparative Analysis of Different Techniques
S. Proposed Antenna Technique Applied Remarks
No.
1. Implementation of Slotted Meander- A Defect is introduced called as To enhance isolation in microstrip patch
Line Resonators for Isolation meander line resonator by creating antenna arrays and it has concluded that that
Enhancement in microstrip Patch defect known as band notch technique only implemented on array
Antenna Arrays function. Resonator is designed to antennas.
block surface current at resonant
frequency of two patch antenna.
2. Wide Band Dual-Beam U Slot Bandwidth of antenna is obtained The proposed design was used for stationary
microstrip Antenna by making use of u shaped patch. terminals of various indoor wireless
Conventional U slot patch antenna, communication networks.
parametric analysis is analyzed.
3. Circular symmetric slotted Obtained by cutting shapes in 3 dB axial-ratio (AR) bandwidth of around
microstrip patch antenna with diagonal directions of microstrip 0.7% (6.0 MHz) with
compact size patch antenna. 2.0% (18.0 MHz) impedance bandwidth was
achieved
4. Triband bowtie antenna using slot Obtained by inserting two pairs of Antenna was resonated at three different
technique slot with different length of bands but its dimensions were made for
isosceles triangle without middle frequency band. This antenna was
increasing area of triangle. resonated for 3.5 GHz, 4.5 GHz and 5.8
GHz.
5. Compact and Small Planar Consists of a rectangular radiating Obtained the required operational frequency
Monopole Antenna with patch with Land U-shaped slots bands—namely,WLAN(2.4/5.2/5.8 GHz)
Symmetrical L- and U- Shaped Slots and ground plane. and WiMAX (2.5/3.5/5.5 GHz).
for WLAN/WiMAX Applications
Antenna was resonated at three different bands but its VI. TECHNIQUES USED TO MODIFY SINGLE
dimensions were made for middle frequency band. This BAND PATCH INTO MULTIBAND
antenna was resonated for 3.5 GHz, 4.5 GHz and 5.8 GHz.
Design and simulation was carried out using antenna Various techniques have been proposed to modify a single
simulation software. band antenna into a multiband antenna.
A. CPW-FED Technique
The designed antenna configuration is depicted in Fig. 15.
As seen, the microstrip antenna composed of two coupled
metallic elements fed by 50-ohm coplanar waveguide
(CPW) line.
B. Proximity Coupled
A corner-truncated rectangular patch with a rectangular slot
at its center is printed on top of the upper layer. The bottom
side metal of this layer is fully etched out. Proximity
coupling is obtained by a meandered microstrip feedline
printed on top of the lower substrate layer. The slotted
ground structure is on the lower side of this substrate.
Length of the upper layer is slightly smaller than the lower
layer in order to keep a provision for connection of inner
conductor of a SMA connector to the microstrip feed.
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International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 6 Issue: 2 133 – 143
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U-slots and L-probe feed, the antenna characteristics can be structure to own the self-similarity geometrical structure.
controlled. The phenomenal expansion in wireless communications has
After conducting parametric studies, a test antenna posed a great challenge to design compact, portable and
was simulated and fabricated. Good agreement between multiband antennas to support several applications. Fractal
simulated and measured response was obtained on all four antennas seen to be a viable solution to meet the challenges.
operating frequencies making it suitable multiband antenna. Therefore active research initiatives are taken up at various
As a variation to U-slots, the slot geometry was slightly to organizations to develop new fractal antennas. These
V-slot with base. V-slot with base MSA gives higher antennas not only have an effective length but the contours
operating frequencies and provided better overall antenna of its shape give a capacitance or inductance to match the
gain. [25] antenna to the circuit.
E. Fractal Technique
Fractal has unique property that it can make copies of itself
at different scales. The concept of fractal antenna is very old
but designing for broadband application is quite new.
The antenna utilized a coaxial feeding technique
and simultaneously possesses multiband, almost uniform
radiation, and low profile. The self-similarity [26] of fractal
gives rise to multiple bands. The length of the fractal at
resonance is increasing due to space filling property,
whereas the height reaches an asymptote reduction allowing
an antenna to operate at lower frequency and shows a low
resonant frequency. In 1970, Dr B. Mandelbrot coined the
term Fractal. Fractal antenna has demand in military as well
as commercial area Mandelbrot explained the complex Figure 18 Basic structure of fractal antenna
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