Performance analysis of Rectangular Microstrip Patch
Antenna on different dielectric Substrates
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 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.
Figure: Structure of a Rectangular Microstrip Patch Antenna.
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
Ground Plane
Figure:Microstrip Antenna
The Patch Width (W) for efficient radiation is given as;
W=Vo/2fr under root (2/dielectric constant+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 = dielectric constant +1/2 +die electric constant-1/2[1=12*h/2]
power -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 under root effect dielectric constant
The Length Extension ( delta L) is given as:
Delta L = 0.412h (effective dielectric constant +0.3)(w/h+0.264)/(effective dielectric constant 0.258 )(w/h+0.8)
The Patch Length (L).
The actual patch length now becomes;
Leff -2 delta L
The Bandwidth (BW)BW=3.77((dielectric constant-1/square of dielectric constant))(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 under root effective dielectric constant
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 (9)
Wg = 6h + W (10)
Where, Lg and Wg are the plane ground dimensions along the patch length and width
respectively.
PARAMETERS
FREQUENCY
HEIGHT(H)
DIELECTRIC
CONSTANT(εr)
WIDTH(W)
LENGTH
Duroid 5880
2
1.57
2.2
SUBSTRATES
FR4
2
1.6
4.35
Alumina
2
1.5
9.8
59.25
49.27
47.40
36.73
32.25
23.55
FOR DIELECTRIC CONSTANT-2.2
Width(mm)
10
20
30
40
50
60
70
Frequency(GHZ)
11.8
5.92
3.95
2.96
2.37
1.97
1.69
Dielectric substrate(Er)
2.2
2.2
2.2
2.2
2.2
2.2
2.2
80
1.88
2.2
FOR DIELECTRIC CONSTANT-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
FOR DIELECTRIC CONSTANT-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
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
Dielectric Dielectric
Substrates constant
Duroid
5880
FR4
alumina
2.2
Gain(DBI) Peak
Minimum Reflection
Band
impedance(ohm) VSWR
coefficient(dB) width(dB)
value
7.50
49.9
1.08
-27.8
21.5
4.0
9.8
6.15
5.14
48.7
45.1
1.11
1.18
-25.4
-21.5
17.3
8.7
Conclusion:- 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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