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ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
Review of Microstrip Patch Antenna Array
Technology
Devang V. Katrodiya1, Jishnu N. Peshavaria2, Vivek Ramamoorthy3
B.E. Scholar, Dept. of E.C., Marwadi Education Foundations Group of Institutions, Rajkot, Gujarat, India1,2
Asst. Professor, Dept. of E.C., Marwadi Education Foundations Group of Institutions Rajkot, Gujarat, India 3
ABSTRACT: The recent development in the antenna technology is the prime requirement in order to support
development in the communication system. The development of microstrip patch antennas has been enhanced due to its
versatility in terms of resonant frequency, polarization, radiation pattern and impedance. This paper gives flow from
microstrip patch antenna, its array to the recent trends of its development technology.
KEYWORDS:microstrip patch; array; reconfiguration; switches; gain; directivity; radiation pattern; polarization;
frequency
I.
INTRODUCTION
The antenna can be defined as “a means for radiating or receiving radio waves” according to the IEEE standard
definition of antenna [1]. The wireless communication takes place in the form of electromagnetic signal and so the
study of antenna is therefore important. The recent development in the field of antenna technology has been accelerated
along with the development in the communication field.
Microstrip patch antenna offer wide variety of advantages like low profile, planar and simple structure due to which it
is cost-effective as compared to other antenna like loop antenna, horn antenna, helical antenna and Yagi-Uda antenna
[1]. The present paper gives the basic study of the microstrip patch antenna and it proceeds towards the study of
microstrip patch antenna array in order to overcome limitations of single microstrip patch antenna. Finally, it also
presents recent trends in microstrip patch antenna array technology.
II.
MICROSTRIP PATCH ANTENNA
The microstrip patch antenna consists of basically three layers: conducting patch, substrate layer and ground layer.
Fig.1 represents the structure of microstrip patch antenna. The patch and the ground plane constitutes any metal
conductor while substrate constitutes of dielectric material. The relative permittivity ( ) of dielectric material is
usually in the range of 2.2 ≤ ≤ 12 [1]. The feeding in the microstrip patch antenna can be broadly classified into four
ways: microstrip line feed, coaxial probe feed, aperture-coupling feed and proximity coupling feed. By proper
impedance matching between the feed and the antenna, the input power fed through the feed is coupled to the antenna
with minimum losses. It supports linear as well as circular polarization.
The antenna supports fixed mode of propagation at least over a specific range of frequencies if the transmission line
system is filled with a uniform dielectric. Microstrip does not have uniform dielectric filling and thus it does not
support single mode of propagation but supports Quasi-TEM mode which closely resembles TEM mode [2].
In the microstrip patch antenna, the shape of the patch can be any regular geometrical or even irregular shape but for
simplicity in design analysis generally rectangular, square or circular shape is taken [1]. Circular sector shaped patch
can also be taken as it has smaller dimensions as compared to rectangular and circular patch and it also provides
circular polarization which is required for wireless communication [4]. The operating frequency of the microstrip patch
antenna depends on the dimension of the patch. The dimension of the patch reduces for designing antenna at the higher
frequencies. The lower and upper bands of resonant frequencies are controlled by the length and width [5].
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101
ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
The various ways to increase the bandwidth of the microstrip patch antenna are: i) increasing the substrate height ii)
proper impedance matching iii) reducing substrate effective permittivity iv) by multiple resonance operation. But on
increasing the height of the substrate, the radiation efficiency decreases for frequencies less than 10 GHz and on
reducing the substrate height, relative permittivity increases the radiation efficiency. Thus, for antennas operating at
frequencies less than 10 GHz, thin substrates with less relative permittivity should be used [7].
The feeding technique used also affects the performance of microstrip patch antenna. For a thick dielectric substrate,
the microstrip line feed and the coaxial feed has numerous disadvantages i.e. for thicker substrates, more probe length
is required which makes the
input impedance
more
inductive and cause matching
problems [3].
Fig.1microstrip patch antenna structure
The probe feed method has much more positioning errors ascompared to aperture-coupled feed. The aperture-coupled
feed technique when used even with traditional patch design, it substantially increases the bandwidth beyond few
percent. By using off-center coupling apertures or apertures with crossed slots, circular polarization can be obtained
with good axial bandwidth [5].
For the transmission line method of analysis, the design equations (1-5) [1] for designing the microstrip patch antenna
of patch length L, width W , height of substrate h and relative dielectric constant are as follows:
(1)
where, is velocity of light in freespace.
The patch dimensions are finite along the length and width of the patch due to which the fields undergo fringing at the
edges of the patch as shown in Fig.2 .The fringing effect thus makes electrical dimensions of the microstrip patch to
appear wider as compared to physical dimensions and this is accounted in the resonant frequency in the form of
effective dielectric constant
[1].
The effective dielectric constant is obtained using “(2)”.
(2)
Fig.2 Fringing in microstrip patch antenna
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102
ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
(3)
(4)
(5)
There has been various attempts in enhancement characteristics of single microstrip patch antenna and numerous
methodologies have been used for it. In one of the proposed antenna, fractal geometry in the microstrip patch antenna
was used which is the potential candidate for multiband applications like that for Wi-Fi. This type of antennas provide
an increase in directivity with reduction in physical size of the patch. [13].
The microstrip patch antenna also has some of the disadvantages such as very narrow frequency bandwidth, low
efficiency, low power operation, poor polarization polarity and high quality factor. Because of these reasons, microstrip
patch array is used.
III.
MICROSTRIP PATCH ANTENNA ARRAY
Microstrip patch antenna arrays are used to achieve the required radiation pattern which cannot be achieved with a
single element. The array structure enhances the directivity, used to scan the beam of an antenna system and performs
various functions which are possible only using array structure [1]. Fig. 3 shows the microstrip patch antenna array,
which is an array of rectangular microstrip patches on a common substrate and ground layer.
The microstrip patch antenna array elements can be fed by a single feed line or multiple feed line, known as series feed
method or corporate feed method respectively [1].The series feed method is a compact and simple feeding method but
has more return loss and poor directive gain. The corporate feed method provides higher radiation efficiency than series
feed antennas and provides better directivity and comparative low return loss but requires a larger area. The corporateseries feed array is a combination of series feed array and corporate feed array and provides more directivity with
moderate return losses with an advantage to have less area requirement for feeding [7].
The array can be defined by the number of array elements, distance between elements d (Fig. 3), array geometry and
phase of excitation. The number of array elements increases the overall gain of the antenna. The increase in inter-element
spacing makes the beam widths of all major lobes narrow and increases the number of minor lobes, also the direction of
all major lobes for each element are not fixed while varying the distance between elements by introducing aphase shift
between elements, the position of the main beam can be steered [4].
Fig. 3 Microstrip patch antenna array
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103
ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
The linear arrays provides increase in directivity as well as gain but it does not allow to scan the beam in more than one
dimension.Planar arrays provides high directivity, symmetrical patterns with low side lobes and directional beams and
the main beam can be pointed to any direction with the planar geometry. But the gain and directivity of the planar array
antenna is lower than that in the linear array for the same number of elements. For a rectangular patch and circular
sector shaped patch microstrip antenna, the gain increases in both cases on increasing the number of elements but the
gain of circular sector antenna array is more than that of rectangular patch antenna array for same number of elements
[4].
In the proposed 2×2 microstrip patch antenna array, at 2.4 GHz, 12dB gain was achieved with 40 beam width in Eplane and 26 beam width in H-plane. The obtained gain is improved as compared to single microstrip patch antenna.
This work gives an insight that microstrip patch antenna array is advantageous as compared to single microstrip patch
antenna. [12].
The microstrip patch antenna array of 16-elements with microstrip line feed can also be designed with the feeding
structure on the same plane as that of the patch (case-1) or on different plane with an air gap distance below the plane
of patch (case-2). On analyzing the two cases for the antennas with same features and same number of elements, the
performance of antenna in case-2 would be comparatively higher gain, low return loss and reduction in side lobe to
main lobe ratio. Also, the two dimensional size of the array antenna decreases in case-2 as compared to case-1 due to
decrease in two dimensional planar area requirement [6].The technological enhancement of the microstrip patch
antenna array can be further done by reconfiguration and many researches are undertaken in this field.
IV.
RECONFIGURABLE MICROSTRIP PATCH ANTENNA ARRAY
Frequency, radiation pattern, directivity and polarization are the various properties of the antenna. Conventional
microstrip patch antennas have all these properties static, i.e. these are already fixed while designing antenna.
According to the requirement for communication, the microstrip patch antenna can be designed such that these
parameters of the antenna can be reconfigured, i.e. changed, giving rise to new antenna configuration.
In one of the proposed antenna structure, five circular patch elements are used, with one main center radiator and four
parasitic radiators, A, B, C and D equally spaced around center radiator, in four directions. The parasitic elements can
be activated or deactivated via shorting pin to the ground, which is referred to its ON state or OFF state respectively.
The parasitic element in the ON state functions as reflector and in the OFF state functions as director that will push and
pull the radiation pattern. This structure resembles the Yagi-Uda antenna structure. When the center radiator is in ON
state, with all four pins, pin A, pin B, pin C and pin D in ON state, the beam switching angle (𝟇) obtained is 0. In this
way, by turning pin A, pin B, pin C and pin D in OFF state consecutively, the beam switching angle 45, 135, 225
and 315 is obtained respectively. This also leads to variation in other antenna properties like center frequency,
operating band, gain, efficiency and beam switching angle (𝞱) [8].
Reconfigurable microstrip antenna array had been also designed at UMTS band for adaptive base station using SPST
switches. The proposed antenna consists of circular patches fed by tree shaped microstrip line having four branches.
Each branch consists of two circular patches which functions as radiators and three circular patches coupled by
radiators to function as directors, similar to Yagi-Uda antenna. SPST (Single Pole Single Throw) switches are used in
order to have reconfigurability which are placed in each branch of the distribution network. According to the state of
the switch, either all four subnet branches are fed or three, two or one subnet branches are fed accordingly and in this
way either four active branches, three, two or one active branch is obtained. The increase in number of active branches
leads to increase in gain, directivity and decrease in beam angle and hence change in radiation pattern is obtained [9].
There had also been considerable attempts to have frequency, radiation pattern and polarization reconfiguration in the
microstrip patch antenna array. The proposed antenna structure consists of a pixelized array of 6×6 pixelized array fed
by driven patch, both fabricated on Rogers RO4003 substrate. The patch was designed to operate at 2.5 GHz. PIN
diodes are used between pixels to have reconfigurability. The experimental result proves that pixel size below λ/10
provides good reconfigurability. The compound reconfiguration of the antenna had been obtained by six resonant
Copyright @ IJIRCCE
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104
ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
frequencies 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 GHz,with five direction-of-arrival(DOA) angles -30, 0 and 30 for 𝞱 and 0,
90 for 𝟇 and four polarizations, horizontal, vertical, LHCP and RHCP with different gain [10].
The Antennas can make the communication system much more robust. The MIMO (Multiple Input Multiple Output)
communication system is now preferred for communication and so for that MIMO antenna technology has been
developed. In the proposed antenna, a unified technology for both the metallic pixel patches and the MEMS (MicroElectro-Mechanical Systems) switches was used. The MEMS switches has an advantage to be constructed along with
the microstrip patch antenna, thus reducing the design cost as the MEMS and the pixel-patches shares a common
substrate layer. The silicon-crystal substrate was used for MEMS which were made similar to the structure of
microstrip patch. The MEMS switches were placed between the pixels. The feeding was provided diagonally by
coplanar waveguide (CPW) stub [11].
In this configuration, on exciting the patches in only horizontal direction with one line of patches left unexcited
generates horizontal polarization and similarly vertical polarization can be obtained by exciting patches only in vertical
direction. Also, another feature it had was that when two border single-patch rows, one horizontal and one vertical
where deactivated, the frequency tuning of the reconfigurable MEMS antenna varies linearly with a small constant step
change in excitation of pixel rows and columns. This antenna provides an increase in spectral efficiency, SINR (Signal
to Interference and Noise Ratio), system capacity and lowers the requirement of power. For the MIMO systems, the
throughput of wireless networks can be improved using beamforming, beam-steering spatial multiplexing and transmit
and receive diversity. Antennas can be designed to exhibit these mechanisms which contribute to improve the
communication system [11].
V.
CONCLUSION
The microstrip patch antenna technology has been considerably improved and still many researches are undertaken to
improve this technology. From the basic microstrip patch structure to the microstrip patch array was enhanced
structurally along with functionality.
This comparative study of various trends in the microstrip antenna technology gives an insight for microstrip patch
antenna development. The antenna property depends on the physical structure and interconnections through the feed.
Hence, from this analysis, it is concluded that the microstrip patch antenna functions can be further enhanced by use of
switches, which can change the antenna characteristics by changing physical interconnections. The project undertaken
by us resembles closely with recent development in antenna technology. There has been an attempt to design a
microstrip patch antenna array with improved structure and functionality in terms of radiation pattern, gain, directivity
and frequency.
ACKNOWLEDGMENT
We are thankful to God for being bestowed to undertake project in the field of antenna development. The never ending
support of our parents and their blessings led us to this stage of knowledge and we are greatly thankful to them. We are
greatly thankful to our guide, Professor R. Vivek for his guidance and thrust provided to lift us to accomplish the
project and Professor S. Kashyap, Professor Shivakrishna Dasi and Professor Vishal Sorathiya for helping us whenever
required.
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ISSN(Online): 2320-9801
ISSN (Print): 2320-9798
International Journal of Innovative Research in Computer and Communication Engineering
An ISO 3297: 2007 Certified Organization
Vol.3, Special Issue 3, April 2015
2nd National Conference On Emerging Trends In Electronics And Communication Engineering (NCETECE’15)
Organized by
Dept. of ECE, New Prince Shri Bhavani College Of Engineering & Technology, Chennai-600073, India during 6th & 7th April 2015
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