PERFORMANCE ANALYSIS OF RECTANGULAR MICROSTRIP PATCH ANTENNA ON
DIFFERENT DIELECTRIC SUBSTRATS
ANKITA TOMAR ,SWETA SHARMA & AMIT RATHI
Department of Electronics, Banasthali University, Tonk, Rajasthan, India
ABSTRACT
This study presents the theoretical and experimental investigation on the effect of width on resonance frequency, MSA
bandwidth is greatly affected by the dielectric substrates.A Microstrip antenna (MSA) is well suited for wireless
communication due to its light weight, low volume and low profile planar configuration which can be easily conformed to
the host surface. Larger bandwidth can be achieved by using a thicker substrate with a lower dielectric constant value. In
this paper, the effect of various dielectric constants on rectangular microstrip patch antenna performance is investigated.
The simulated and measured result is obtained then the width remains same and frequency changes .In this paper we take
three dielectric substrates as Duroid 5880, FR4, Alumina and the value of these substrates are same for a particular
frequency. The resonant frequency and the bandwidth are gradually decreases with the increase lengths. The resonant
frequency gradually decreases as we increase the length because of lengthening the current path due to the slot which
means the half wave length along the radiating edge increases gradually.
KEYWORDS - Microstrip Antenna (MSA), Resonance frequency, Width, height
INTRODUCTION
This paper analyses the effect of various dielectric constants in the design of rectangular MPA. The requirement,
microstrip patch antennas (MPAs) have been proposed.
Microstrip patch antennas are commonly used in aircraft, spacecraft, satellite, and mobile communication and
missile applications due to their many attractive features such as simple structure, low production cost, light weight and
robustness. Due to the advancement of technology microstrip patch antennas are used in modern printed circuit technology,
MMIC design, GPS communication system, Wireless Local Area Network (WLAN), Synthetic Aperture Radar (SAR).
There are numerous substrates that can be used for the design of MPAs and their dielectric constants are usually in
the range of 2.2 ≤ εr ≤ 12. MPAs radiate primarily because of the fringing fields between the patch edge and the ground
plane. The radiation increases with frequency increase and using thicker substrates with lower permittivity, and originates
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mostly at discontinuities. The dielectric constant is the ratio between the stored amount of electrical energy in a material
and to that stored by a vacuum.
A thick dielectric substrate having a low dielectric constant is more desirable as it provides better efficiency,
larger bandwidth, and better radiation. The lower the dielectric constant is, the better the material works as an insulator.
we use these parameters are length, width, height, dielectric constant and resonating frequency in which length
and width taking constant The range of dielectric constant lies in between 2.2 to 12. Lower the dielectric constant, we get
better performance of MPA. when we increase the values of dielectric constant then frequency will decrease gradually. So
we can say that in other words dielectric constant is inversely proportional to the frequency.
RECTANGULAR MICROSTRIP PATCH ANTENNA DESIGN
In its most basic form, a microstrip patch antenna consists of a radiating patch on one side of a dielectric substrate
and a ground plane on the other side as shown in Figure 1. The bottom surface of a thin dielectric substrate is completely
covered with metallization that serves as a ground plane.
The rectangular MSA is made of a rectangular patch with dimensions width (W) and length (L) over a ground
plane with a substrate thickness (h) and dielectric constant (Er ) as shown in Figure 1. There are numerous substrates that
can be used for the design of MSAs, and their dielectric constants are usually in the range of 2.2 < εr < 12
Figure 1: Structure of a Rectangular Microstrip Patch Antenna
The Patch Width (W) for efficient radiation is given as;
W=Vo/2fr √( 2/εr + 1)
Where, W is the patch width, vo is the speed of light, fr is the resonant frequency, and is the dielectric constant of
the substrate.
The Effective Dielectric Constant ( ) - Due to the fringing and the wave propagation in the field line, an
Effective dielectric constant (εreff) must be obtained.
Effective dielectric constant = εreff = εr +1/2 + εr -1/2[1=12*h/2] p-1/2
Where, εreff is the effective dielectric constant, h is the height of the dielectric substrate.
The Effective Length ( ) for a given resonance frequency fr is given as;
Effective length= c/2fr √ εr
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The Length Extension (delta L) is given as:
Delta L = 0.412h (εreff +0.3) (w/h+0.264)/(εreff -0.258 )(w/h+0.8)
The Patch Length (L).
The actual patch length now becomes;
Leff -2 Δ L
The Bandwidth (BW)Bw=3.77((
-1/
))(W/L)(H/ wave length of free space)*100%
The Feed Co-ordinates.
Using coaxial probe-fed technique, the feed points are calculated as;
Yf = W/2
Xf=L/2√εreff
Where, yf and xf are the feed co-ordinates along the patch width and length respectively.
The Plane Ground Dimensions:- It has been shown that MSAs produces good results if the size of the ground
plane
is greater than the patch dimensions by approximately six times the substrate thickness all around the periphery
Lg = 6h + L
Wg = 6h + W
Where, Lg and Wg are the plane ground dimensions along the patch length and width respectively.
Table 1: Different Substrates
PARAMETERS
SUBSTRATES
Duroid 5880
FR4
Alumina
FREQUENCY
2
2
2
HEIGHT(H)
1.57
1.6
1.5
DIELECTRIC
CONSTANT(εr)
2.2
4.35
9.8
WIDTH(W)
59.25
47.40
32.25
LENGTH
49.27
36.73
23.55
Table 2:For Dielectric Constanr -2.2
Width(mm)
Frequency(GHZ)
Dielectric substrate(Er)
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10
20
30
40
50
60
70
80
11.8
5.92
3.95
2.96
2.37
1.97
1.69
1.88
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
Table 3:For Dielectric Constanr -4.35
Width(mm)
10
20
30
40
50
60
70
80
Frequency(GHZ)
9.15
4.57
3.05
2.28
1.83
1.52
1.30
1.14
Dielectric constant(Er)
4.35
4.35
4.35
4.35
4.35
4.35
4.35
4.35
Table 4:For Dielectric Constanr -9.8
Width(mm)
10
20
30
40
50
60
70
80
Frequency(GHZ)
6.45
3.22
2.15
1.61
1.29
1.07
0.92
0.80
Figure 2: Patch Width vs Resonant Frequency (GHZ)
Width (mm)
Dielectric constant(Er)
9.8
9.8
9.8
9.8
9.8
9.8
9.8
9.8
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Table 5:Final Conclusion for Different Substrate
Dielectric
constant
Gain(DBI)
Peak
impedance(ohm)
Minimum
VSWR
value
Reflection
coefficient(dB)
Band
width(dB)
Duroid
5880
2.2
7.50
49.9
1.08
-27.8
21.5
FR4
4.0
6.15
48.7
1.11
-25.4
17.3
alumina
9.8
5.14
45.1
1.18
-21.5
8.7
Dielectric
Substrates
CONCLUSIONS
From the simulation it was shown in table that frequency gradually decreases by increasing width and dielectric
constant remains same for a particular substrate. The results prove that using a substrate material with a lower dielectric
constant in design of MPA leads to better antenna performance. From this paper, it can be clearly seen that substrate
material and specifically the dielectric constant effectively determines the performance of a rectangular microstrip patch
antenna.
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