International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
Design and Implimentation of Microstrip Circular Patch
Antenna for RFID Application
Mr. Sachin B. Pawar1
M.E. scholar (Digital Electronics),
S.S.T.’s C.O.E.T., Bambhori, Jalgaon (M.S.)-425001
Mr. A. H. Karode2
Asst. Prof. , Electronics and Telecomm. Department
S.S.T.’s C.O.E.T., Bambhori, Jalgaon (M. S.)-425001
Dr. S. R. Suralkar3
Prof. & HOD , Electronics and Telecomm. Department
S.S.T.’s C.O.E.T., Bambhori, Jalgaon (M.S.)-425001
Abstract- First short distance communication between
humans was by sound through voice. With the desire for
slightly long distance communication came, instruments
such as drums, then, visual system such as signal flags
and smoke were used. These visual communication
devices, of course, utilized the light portion of the
electromagnetic spectrum. It has been only very recent
in human history that the electromagnetic spectrum,
outside the visible region, has been employed for
communication, through the use of radio. One of
humankind’s
greatest
natural
asset
is
the
electromagnetic spectrum and the transmitter and
receiver has been instrumental in harnessing this
resource. Circularly polarized single feed microstrip
patch antennas are widely applicable in RFID(Radio
Frequency Identification), radar and GPS systems.
Achieving near about 3dB axial ratio , bandwidth is a
challenging task for designers. The paper provides a
detailed study of how to design of a coaxial-fed
Microstrip circular Patch Antenna using IE3D software
and implement design on FR4 substrate for RFID
application.
In the few years microstrip patch antenna has obtained
lot of popularity and considered as most dynamic field
in communication. [3] An microstrip patch antenna can
have different shape of patch liked rectangular, circular,
triangular, elliptical etc. Each antenna configuration has
a radiation pattern and design parameters, in addition to
their advantages and drawbacks. In this paper, however,
the focus is specificallyon 850 to 960 MHz frequency
range circular patch microstrip patch antenna , which is
used for RFID application in various countries.[1]
Fig.1 Circular patch antenna
Key words- Antenna, Microstrip patch antenna, RFID
2. DESIGN DESCRIPTION
1. INTRODUCTION
An antenna is defined as a “Transmitting or
receiving system that isdesigned to radiate or receive
electromagnetic waves” by the IEEE. A list of some
common types of antennas is wire, aperture, microstrip,
reflector, and arrays.Microstrip antennas are classify
into 4 different categories they are:
Microstrip Patch antenna
Printed slot antennas
Microstrip dipoles
Microstrip travelling wave antenna
ISSN: 2231-5381
The patch acts approximately as a resonant cavity
(with short-circuit (PEC) walls at top and bottom and it
acts as open-circuit (PMC) walls on the edges).In a
cavity, only certain modes are allowed to exist, at
different resonance frequencies. If the antenna is excited
at a resonance frequency, a strong field is set up inside
the cavity, and a strong current on the (bottom) surface
of the patch. This produces significant radiation (a good
antenna). Generally antenna radiates an elliptical
polarization, which is defined by three parameters: axial
ratio, tilt angle of antenna and sense of rotation. When
the axial ratio is infinite or zero, the polarization pattern
becomes linear with the tilt angle defining the
polarization. The quality of linear polarization is usually
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
indicated by the level of the cross polarization. For the
unity axial ratio, a perfect circular polarization results
and the tilt angle is not applicable. In general the axial
ratio is used to specify the standard quality of circularly
polarized waves. Antennas produce circularly polarized
waves pattern when two orthogonal field components
with equal amplitude but in phase quadrature are
radiated. Various antennas are capable of fulfil these
requirements. They can be classified as a resonator and
traveling-wave types. A resonator-type antenna consists
of a single patch antenna that is capable of
simultaneously supporting two orthogonal modes in
phase quadrature or an array of linearly polarized
resonating patches with proper orientation and phasing.
A traveling-wave type of antenna is usually constructed
from a microstrip transmission line. It generates circular
polarization pattern by radiating orthogonal components
with appropriate phasing along discontinuities is the
travelling-wave line. [5],[7],[11]
(b)
Fig. 3 The lower square slotted patch with microstrip
stub (a) and the upper square slotted patch (b).[1]
Length (L1) of The feed is on the diametric. The patch is
nearly square. And length of this antenna is 79.5mm. In
this design we take L=W=79.5mm as shown in
following fig. 4 .
Fig. 4 Length and width of antenna
Fig.2 A cross-sectional view of the proposed stacked
square slotted microstrip antenna.[1]
And radius of circular patch is given as
(2.1)
Therefore the radius of antenna is near about 15mm.
And Xo=72.75mm in which M1=35mm,
(a)
Fig. 5 Circular patch
3. IMPLIMENTATION OF ANTENNA
The three important parameters for the design of a
rectangular Microstrip Patch Antenna are:
ISSN: 2231-5381
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
Frequency of operation (fo):
The resonant frequency of the antenna must be
selected appropriately. The RFID Systems uses the
frequency range from 850Mhz-960MHz.We select
this range because in various countries defferent
frequency ranges are used for this application. The
system operates at the bands of 902–928 MHz in
America, 840–955 MHz in Asia-Pacific region and
865–867 MHz in EuropeIn Asia-Pacific region, the
UHF RFID frequency range is different in different
countries: China (840.5–844.5 MHz, 920.5–924.5
MHz), Japan (952–955 MHz), India (865–867
MHz), Korea (908.5–910 MHz, 910–914 MHz),
Hong Kong (865–868 MHz, 920–925 MHz),
Taiwan (920–928 MHz), Singapore (866–869 MHz,
923–925 MHz), Australia (920–926 MHz), etc.
Hence the antenna designed must be able to operate
in this frequency range.[1]
Dielectric constant of the substrate (εr):
The most commonly used substrates are,
 Honeycomb(dielectric constant=1.07)
 Duroid(dielectric constant=2.32)
 Quartz(dielectric constant=3.8)
 FR4(dielectric constant=4.4)
 Alumina(dielectric constant=10)
The bandwidth is directly proportional to
substrate thickness h. The dielectric material
selected for proposed design is FR4 which has
a dielectric constant of 4.4.
Height of dielectric substrate (h):
For the microstrip patch antenna to be used in RFID
system, it is importantthat the antenna is not bulky.
Hence, the height of the dielectric substrate is selected in
the mm.We select it 3.2mm. The circular patch antenna
with CPW feed structure on FR4 substrate of length
xwidth dimensions are 79.5mm*79.5 mm as shown in
Fig. All the shown dimensionsare measured &
optimized by using IE3D Simulator.The hardware
design of the implemented antenna is as shown in
following photographs[8]
Fig.6 3D view of antenna using IE3D software
Fig. 7 Front view of implemented antenna
Fig. 8 Back view of implemented antenna
4. RESULTS
4.1 VSWR
Graph 4.1 shows the VSWR variations with respect
to Frequency. The VSWR(Voltage Standing Wave
Ratio) is the ratio of the maximum to the minimum RF
voltage along the transmission line.(Software result)
Table 1 Detail of geometry dimention
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
Graph 4.1 VSWR (Software result)
Graph 4.3 Return loss (software result)
From the simulated result , the VSWR value ranges
from 1 to 2 throughout the desired frequency range.The
VSWR(Voltage Standing Wave Ratio) is the ratio of the
maximum to the minimum RF voltage along the
transmission line.(Hardware result)
The hardware testing of the proposed antenna is done on
network analyzer, Hardware gives frequency response
from 850Mhz to 960Mhz
Graph 4.2 VSWAR (Hardware result)
Graph 4.4 return loss (Hardware result)
From the hardwareresult , the VSWR value ranges from
1 to 2 throughout the desired frequency range.
4.3 GAIN
4.2 RETURN LOSS
The simulation of the proposed antenna is done on IE3D
software, Simulation gives frequency response from
850Mhz to 960Mhz
Graph 4.5 Gain vs Frequency
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International Conference on Global Trends in Engineering, Technology and Management (ICGTETM-2016)
[9]
4.4 AXIAL RATIO
[10]
[11]
[12]
[13]
[14]
Graph 4.6 Axial ratio vs Frequency
[15]
5. CONCLUSION
In this paper work, microstrip circular patch antenna is
design using IE3D software and is successfully
implemented it on substrate FR4 with CPW feed. The
simulated result gives return loss less than -10dB from
850MHz to 960MHz , which is more than 100% of
RFID range, having satisfactory VSWR, Return loss ,
Gain and Axial ratio which shows that antenna is having
good potential & small size. These attributes makes this
antenna applicable for all RFID technology.
[16]
[17]
N. Herscovici, Z. Sipus, and D. Bonefacic, “Circularly Polarized
Single-Fed Wide-Band Microstrip Patch,” IEEETransactions on
Antennas and Propagation, AP- 51, 6, June 2003, pp. 1277-1280.
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