83
CHAPTER 4
EFFECT OF DIELECTRIC COVERS ON THE PERFORMANCES OF
MICROSTRIP ANTENNAS
4.1. INTRODUCTION
In the previous chapter we have described effect of dielectric thickness on antenna
performances. As mentioned the main objective of this chapter is to find the environmental
impacts on the various patch antennas such as square and pentagonal patch with various
dielectric covers which is linearly polarized having the resonant frequency of 2.45 GHz
(with 10% bandwidth), using FR4 (epoxy), as the dielectric substrate material of 0.8 mm
thickness. The relative permittivity of the dielectric material is 4.4. The main reason behind
selecting this frequency range is that the antenna is used in WLAN (wireless-LAN)
systems. As there are many environmental factors which affect the normal working of the
microstrip patch antennas.
Hence it is important to study the performance variation of the microstrip patch antenna
due to various climatic conditions such as snow, dust- particles and Plexiglas, NelTec,
Glass PTFE and Rogers. As we know that in rainy conditions the water layer is formed due
to adhesion and surface tension and its actual instantaneous thickness depends upon
number of factors such as, exact orientation of patch surface (if patch surface is slightly
inclined, the gravitational force will play its part accordingly), rate of precipitation, wind
condition, humidity etc.
4.2. DESIGNING OF DIELECTRICS LOADED PATCH ANTENNAS
In order to study the effect of dielectric loading of different dielectric constant on the
performance behavior of square patch antenna, the optimum design parameters are selected
to achieve the compact dimensions as well as the best possible characteristics such as high
radiation efficiency, high gain, directivity and bandwidth. The proposed antenna structure
is fed with 50 ohms coaxial cable for impedance matching and HFSS simulation tool has
been used for the analysis, which offers multiple state-of the-art solver technologies, each
84
based on the finite element method. The obtained results reveal that dielectric loading do
not change only the resonance frequency but also affects the other parameters; gain,
directivity and bandwidth. In particular, the resonance frequency lowers and shift in
resonant frequency increases with the dielectric constant of covers. In addition, it has also
been observed that return loss and VSWR increases, however bandwidth and directivity
decreases with the dielectric constant of dielectrics.
4.2.1. Design of Square Patch Antenna
The patch antenna that introduces here has made of the conduction material copper (Figure
4.1).
Figure 4.1 Structure of square patch antenna
The geometry of square patch antenna having a dielectric cover is shown in Figure 4.2.
Figure 4.2 Structure of antenna with dielectric cover
85
4.2.2. Design Specifications
The proposed square patch antenna was designed using following specifications:
Relative permittivity of the substrate εr = 2.33
Design frequency f0 = 2.4 GHz
Loss tangent of substrate tanδ = 0.001
Height of the substrate h =1.575 mm
Length of patch antenna L= 55.75 mm
Height of the dielectric h =1.575 mm
Relative permittivity of the dielectrics εr = 2.2, 2.5 and 3.02
Dielectric cover materials NelTec, Glass PTFE, Rogers
In reality, the microstrip antenna attached to an electronic device will be protected by a
dielectric cover (dielectric) that acts as a shield against hazardous environmental effects.
These shielding materials normally plastics (lossy dielectric) will decrease the overall
performances of the antenna operating characteristics such as resonant frequency,
impedance bandwidth and radiating efficiency. A transmission line has the line capacitance
C. Suppose all the dielectric layers are removed from this structure. The remaining
conductor system has the line capacitance C0, which is smaller than C. The theory of a
distributed parameter transmission line gives a relation between the wavelength of an
unloaded line λ0 and the guide wavelength of a capacitance-loaded line λ
Similarly, it gives a relation between the characteristic impedance of the unloaded line Z0
and the characteristic impedance of the capacitance-loaded line Z
As is well known in the TEM transmission theory, is identical to the free-space
wavelength, and Z0 is given by
86
Where c is the velocity of light.
Characteristic Impedance and Phase Velocity
The characteristic impedance Z0 and the phase velocity vp of a TEM transmission line can
be written as [1]
Where C and C0 are the capacitances of the transmission line structure with and without
dielectric, respectively, εe is the effective dielectric constant which takes into account the
effect of the fringing fields in the substrate, the sheet material, and the free space, and c is
the velocity of light in free space. The mode considered here is a quasi-TEM mode. The
expression for the capacitance is obtained using the variational method.
For a matched antenna, the change in the fractional resonant frequency relative to the
unloaded case can be calculated using the following expression [2]
The first-order change in the resonant frequency may be expressed as
87
Where εe0 is the effective dielectric constant without cover.
The reason behind alteration of performance of the antenna is that, due to dielectric loading
the characteristic impedance and phase-velocity are modified as mentioned earlier.
4.2.3. Result of Square Patch Antenna with Various Dielectric Covers
In order to observe the effects of dielectric covers on the antenna characteristics, the
proposed antenna has been analyzed using dielectric cover of dielectric constant 2.2, 2.5
and 3.02. The obtained characteristics are shown in Figures 4.3-4.9; however the
corresponding data are tabulated in Table 4.1[3-4].
Figure 4.3 S-parameter of square patch antenna with various dielectric covers
-40
-35
-30
-25
-20
-15
-10
-5
0
1.8 2 2.2 2.4 2.6
Retu
rn
Loss
(d
B)
Frequency (GHz)
Neltec
Glass PTFE
Rogers
88
Figure 4.4 VSWR with various dielectric covers
Figure 4.5 Gain with various dielectric covers
(εr = 2.2) (εr = 2.5) (εr = 3.02)
Figure 4.6 Directivity with various dielectric covers
1
1.5
2
2.5
3
1.8 2.1 2.4
VS
WR
Frequency(GHz)
Neltec
Glass PTFE
Rogers
-10-9-8-7-6-5-4-3-2-10123
-200 -150 -100 -50 0 50 100 150 200
Ga
in(d
B)
Angle,Degree
Neltec
Glass PTFE
Rogers
0
0.2
0.4
0.6
0.8
1
1.2
-200 0 200
Dir
ecti
vit
y
Angle,Degree
0
0.5
1
1.5
2
2.5
-200 0 200
Dir
ecti
vit
y
Angle,Degree
0
0.5
1
1.5
2
-200 0 200
Dir
ecti
vit
y
Angle,Degree
89
(εr = 2.2) (εr = 2.5) (εr = 3.02)
Figure 4.7 Radiation patterns with various dielectric covers
(εr = 2.2) (εr = 2.5) (εr = 3.02)
Figure 4.8 Smith chart with various dielectric cover
(εr = 2.2) (εr = 2.5) (εr = 3.02)
Figure 4.9 Impedance with various dielectric cover
-20
-10
0
10
20
30
40
50
60
1 2 3
Imp
ed
an
ce(O
hm
)
Frequency(GHz) -20
-10
0
10
20
30
40
50
1 2 3Imp
ed
an
ce(O
hm
)
Frequency(GHz)
-10
0
10
20
30
40
50
60
1 2 3
Imp
ed
an
ce(O
hm
)
Frequency(GHz)
90
Table 4.1 Antenna parameters with dielectric loadings
Dielectric
material
Dielectric
constant
(ɛr)
Frequency
(GHz)
Return
loss (dB)
Impedance
(Ω)
Gain
(dB) VSWR
BW
(%)
Directivity
(dB)
NelTec 2.2 2.26 -33.62 51.92 2.0225 1.042 3.62 2.0833
Glass
PTFE 2.5 2.24 -24.12 47.1331 2.52 1.132 3.91 1.8411
Rogers 3.02 2.14 -14.78 37.83 1.0553 1.445 3.49 1.0808
4.3. SQUARE MICROSTRIP PATCH ANTENNA: DESIGN ANALYSIS AND RESULTS
4.3.1. Design Specifications
Feeding technique : Coaxial feed
Substrate material : FR-4
Relative permittivity of the substrate ( ) : 4.4
Design frequency : 2.4-2.4835GHz (ISM band)
Thickness of dielectric substrate : 0.8 mm
Elemental side : 28.6139 mm
Feed location : 8.30158 mm
Coaxial cable dimensions
Inner radius a : 0.635 mm
Outer radius b : 2.0445 mm
4.3.2. Simulated Results
In order to present the design procedure of achieving impedance matching for this case,
dimension of sides of square patch is selected initially be 29.187 mm. After optimization
we met the design challenges such as return losses should be less than -10 dB, VSWR< 2
and low spurious feed radiation.
91
Snow as Dielectric Cover
Apart from rain, many other environmental factors also affect the working of the microstrip
patch antenna installed at any working location. The accumulation of these environmental
factors may degrade the performance of the antenna. The other factors may include snow
accumulation, dust particles accumulation etc. Now we use the snow as the dielectric cover
the antenna patch surface with εr = 1.35 and tanδ = 0.0009. We also observed
that at higher substrate thickness, resonance frequency does not shift significantly.
Return Loss
As shown in the Figure 4.10, with the accumulation of the snow over the patch, the
resonance frequency shifts towards lower value and the return loss increases.
Figure 4.10 Return loss variations with accumulation of snow on square patch antenna
Impedance
As shown in the Figure 4.11, with the accumulation of the snow over the patch, the input
impedance of the antenna will shifts towards lower values. Thus the antenna performance
will get disturbed.
-35
-30
-25
-20
-15
-10
-5
0
1.8 2 2.2 2.4 2.6 2.8
Retu
rn
loss
[d
B]
Frequency [GHz]
dB(S11) at t='0.0mm'
dB(S11) at t='0.1mm'
92
Figure 4.11 Input impedance variations with accumulation of snow on square patch antenna
VSWR
As shown in the Figure 4.12, with the accumulation of the snow over the patch, the VSWR
of the antenna will increases. Thus the antenna performance may get disturbed.
Figure 4.12 VSWR variations with accumulation of snow on square patch antenna
Dust Particles as Dielectric Cover
0
10
20
30
40
50
60
1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9
Imp
ed
an
ce [
Ω]
Frequency [GHz]
impedance at t='0.0mm'
impedance at t='0.1mm'
0
2
4
6
8
10
1.9 2.1 2.3 2.5 2.7 2.9
VS
WR
Frequency [GHz]
VSWR at t='0.0mm'
VSWR at t='0.1mm'
93
Now we use the dust as the dielectric cover over the antenna patch surface with r = 3.0
and tanδ = 0.0062 and found that, it affects antenna performances.
Return Loss
As shown in the Figure 4.13, with the accumulation of the dust particles over the patch, the
resonance frequency shifts towards lower value and the return loss increases.
Figure 4.13 Return loss variations with accumulation of dust on square patch antenna
Impedance
As shown in the Figure 4.14, with the accumulation of the dust particles over the patch, the
input impedance of the antenna will shifts towards lower values. Thus the antenna
performance will get disturbed.
-35
-30
-25
-20
-15
-10
-5
0
2.2 2.3 2.4 2.5 2.6 2.7 2.8
Retu
rn
loss
[d
B]
Frequency [GHz]
(S11) at t='0.0mm'
(S11) at t='0.1mm'
94
Figure 4.14 Input impedance variations with accumulation of dust on square patch antenna
VSWR
As shown in the Figure 4.15, with the accumulation of the dust particles over the patch, the
VSWR of the antenna will increases. Thus the antenna performance will get disturbed.
Figure 4.15 VSWR variations with accumulation of dust on square patch antenna
Plexiglas as Dielectric Cover
Now we use the Plexiglas as the dielectric cover over the antenna patch surface with εr
= 3.40 and tanδ = 0.001.
0
10
20
30
40
50
60
2.2 2.3 2.4 2.5 2.6 2.7
Imp
ed
an
ce [
Ω]
Frequency [GHz]
impedance at t='0.0mm'
impedance at t='0.1mm'
0
2
4
6
8
10
2.2 2.3 2.4 2.5 2.6 2.7
VS
WR
Frequency [GHz]
VSWR at t='0.0mm'
VSWR at t='0.1mm'
95
Return Loss
As shown in the Figure 4.16, with the accumulation of the Plexiglas over the patch, the
resonance frequency shifts towards lower value and the return loss increases.
Figure 4.16 Return loss variations with accumulation of Plexiglas on square patch antenna
Figure 4.17 Input impedance variations with accumulation of Plexiglas on square patch
antenna
Impedance
As shown in the Figure 4.19, with the accumulation of the Plexiglas over the patch, the
input impedance of the antenna will shifts towards lower values. Thus the antenna
performance will get disturbed.
-35
-30
-25
-20
-15
-10
-5
0
2.2 2.3 2.4 2.5 2.6 2.7 2.8
Retu
rn
loss
[d
B]
Frequency [GHz]
(S11) at t='0.0mm'
(S11) at t='0.1mm'
0
10
20
30
40
50
60
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
Imp
ed
an
ce [
Ω]
Frequency [GHz]
impedance at
t='0.0mm'
impedance at
t='0.1mm'
96
VSWR
As shown in the Figure 4.18, with the accumulation of the Plexiglas over the patch, the
VSWR of the antenna will increases. Thus the antenna performance will get disturbed.
Figure 4.18 VSWR variations with accumulation of Plexiglas on square patch antenna
The simulated and measured results have also been tabulated in Table 4.2 and Table 4.3
respectively.
Table 4.2 Antenna performance variation due to accumulation of different materials over
square patch surface
Materials Thickness
(mm)
Resonant
Frequency
(GHz)
% Change
in Resonant
Frequency
Return
Loss
(dB)
Bandwidth (MHz)
VSWR Impedance
(Ω)
Rain Water
0 2.45 0 -31.3528 62.1 0.4702 50.11
0.1 2.175 11.22 -21.1258 49 1.5299 44.42
Snow
0 2.45 0 -31.3528 62.1 0.4702 50.11
0.1 2.3875 2.55 -21.844 58.8 1.408 46.34
Dust Particles
0 2.45 0 -31.3528 62.1 0.4702 50.11
0.1 2.425 1.02 -23.8647 58.8 1.1148 49.5
Plexiglas
0 2.45 0 -31.3528 62.1 0.4702 50.11
0.1 2.4375 0.51 -22.9988 58.7 1.5389 49.33
0
2
4
6
8
10
2.2 2.3 2.4 2.5 2.6 2.7
VS
WR
Frequency [GHz]
VSWR at t='0.0mm'
VSWR at t='0.0mm'
97
4.3.3. Measured Result
Return Loss
Figure 4.19 Return loss variations due to accumulation of water and dust on square patch
antenna
As shown in the Figure 4.19 measured result is in agreement with the simulated results. We
also observed that with accumulation of water and dust particles over the patch the
resonance frequency shifts towards lower value and the return loss increases.
Table 4.3 Measured parameters of the square patch antenna
Materials Resonant
Frequency
(GHz)
% Change in Resonant
Frequency
Return
Loss (dB)
Bandwidth
(MHz)
Normal antenna 2.39 0 -19.28 45
With dust particle 2.18 8.7 -15.19 35
With water level 2.34 2 -28.45 50
Increased water
level 2.21 7.5 -13.71 35
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
1.9E+09 2.2E+09 2.5E+09 2.8E+09
Retu
rn
Loss
(dB
)
Frequency (Hz)
S11(dB)
S11_Dust Particle
S11_water
S11_Increased Water Level
98
4.4. PENTAGONAL MICROSTRIP PATCH ANTENNA: DESIGN ANALYSIS AND
RESULTS
4.4.1. Design Specifications
Feeding technique : Coaxial feed
Substrate material : FR-4
Relative permittivity of the substrate : 4.4
Design frequency : 2.4-2.4835GHz (ISM band)
Thickness of dielectric substrate : 0.8 mm
Elemental side : 19.21 mm
Feed location : 8.21 mm
Coaxial cable dimensions:
Inner radius a : 0.635 mm
Outer radius b : 2.0445 mm
4.4.2. Simulated Results
Initially each side of the pentagonal patch antenna was selected to be equal to 20.23 mm,
which was calculated corresponding to 2.45 GHz (ISM band) but the design challenges
were not met. After optimization and selecting the each side of the pentagon equal to 19.21
mm we met the design challenges such as return loss less than -10 dB, VSWR< 2 and low
spurious feed radiation.
Snow as Dielectric Cover
Now we use the snow as the dielectric cover over the antenna patch surface with εr=
1.35 and tanδ = 0.0009. We observed that at higher substrate thickness, resonance
frequency does not shift significantly.
Return Loss
As shown in the Figure 4.20, with the accumulation of the snow over the patch, the
resonance frequency shifts towards lower value and the return loss increases.
99
Figure 4.20 Return loss variations with accumulation of snow on pentagonal patch antenna
Impedance
As shown in the Figure 4.21, with the accumulation of the snow over the patch the input
impedance of the antenna will shifts towards lower values. Thus the antenna performance
will get disturbed.
Figure 4.21 Input impedance variations with accumulation of snow on pentagonal patch
antenna
-35
-30
-25
-20
-15
-10
-5
0
2.3 2.35 2.4 2.45 2.5 2.55 2.6
Retu
rn
loss
[d
B]
Frequency [GHz]
(S11) at t='0.0mm'
(S11) at t='0.1mm'
0
10
20
30
40
50
60
2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
Imp
ed
an
ce [
Ω]
Frequency [GHz]
impedance at t='0.0mm'
impedance at t='0.1mm'
100
VSWR
As shown in the Figure 4.22, with the accumulation of the snow over the patch, the VSWR
of the antenna will increases. Thus the antenna performance will get disturbed.
Figure 4.22 VSWR variations with accumulation of snow on pentagonal patch antenna
Dust Particles as dielectric cover
Now we use the dust as the dielectric cover over the antenna patch surface with εr
= 3.00 and tanδ = 0.0062.
Return Loss
As shown in the Figure 4.23, with the accumulation of the dust particles over the patch, the
resonance frequency shifts towards lower value and the return loss increases.
Figure 4.23 Return Loss variations with accumulation of dust on pentagonal patch antenna
0
2
4
6
8
10
2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
VS
WR
Frequency [GHz]
(VSWR at t='0.0mm'
(VSWR at t='0.1mm'
-35
-30
-25
-20
-15
-10
-5
0
1.8 2 2.2 2.4 2.6 2.8
Retu
rn
loss
[d
B]
Frequency [GHz]
(S11) at t='0.0mm'
(S11) at t='0.1mm'
101
Impedance
As shown in the Figure 4.24, with the accumulation of the dust particles over the patch, the
input impedance of the antenna will shifts towards lower values. Thus the antenna
performance will get disturbed.
Figure 4.24 Input Impedance variations with accumulation of dust on pentagonal patch
antenna
VSWR
As shown in the Figure 4.25, with the accumulation of the dust particles over the patch, the
VSWR of the antenna will increases. Thus the antenna performance will get disturbed.
Figure 4.25 VSWR variations with accumulation of dust on pentagonal patch antenna
0
10
20
30
40
50
60
2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
Imp
ed
an
ce [
Ω]
Frequency [GHz]
impedance at t='0.0mm'
impedance at t='0.1mm'
0
2
4
6
8
10
2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
VS
WR
Frequency [GHz]
VSWR at t='0.0mm'
VSWR at t='0.1mm'
102
Plexiglas as Dielectric Cover
Now we use the Plexiglas as the dielectric cover over the antenna patch surface with εr
= 3.40 and loss tanδ = 0.001.
Return Loss
As shown in the Figure 4.26, with the accumulation of the Plexiglas over the patch, the
resonance frequency shifts towards lower value and the return loss increases.
Figure 4.26 Return loss variations with accumulation of Plexiglas on pentagonal patch
antenna
Impedance
As shown in the Figure 4.27, with the accumulation of the Plexiglas over the patch, the
input impedance of the antenna will shifts towards lower values. Thus the antenna
performance will get disturbed.
-35
-30
-25
-20
-15
-10
-5
0
2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
Retu
rn
loss
[d
B]
Frequency [GHz]
(S11) at t='0.0mm'
(S11) at t='0.1mm'
103
Figure 4.27 Input impedance variations with accumulation of Plexiglas on pentagonal patch
antenna
VSWR
As shown in the Figure 4.28, with the accumulation of the Plexiglas over the patch, the
VSWR of the antenna will increases. Thus the antenna performance will get disturbed.
Figure 4.28 VSWR variations with accumulation of Plexiglas on pentagonal patch antenna
0
10
20
30
40
50
60
2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
Imp
ed
an
ce [Ω
]
Frequency [GHz]
impedance at t='0.0mm'
impedance at t='0.1mm'
0
2
4
6
8
10
2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6
VS
WR
Frequency [GHz]
VSWR at t='0.0mm'
VSWR at t='0.1mm'
104
The simulated and measured results are tabulated in Tables 4.4 and 4.5 respectively.
Table 4.4 Antenna performance variation due to accumulation of different materials over
pentagonal patch surface
Materials Thickness
(mm)
Resonant Frequency
(GHz)
% Change
in
Resonant Frequency
Return Loss
(dB)
Bandwidth
(MHz) VSWR
Impedance
(Ω)
Rain
Water
0 2.438 0 -28.99 64.1 0.6172 51.95
0.1 2.25 7.69 -23.34 52.2 1.1846 47.42
Snow
0 2.438 0 -28.99 64.1 0.6172 51.95
0.1 2.438 0 -26.3 64.1 0.8418 51.67
Dust Particles
0 2.438 0 -28.99 64.1 0.6172 51.95
0.1 2.413 1.02 -24.84 62 0.9957 51.82
Plexiglas
0 2.438 0 -28.99 64.1 0.6172 51.95
0.1 2.413 1.02 -23.6 58.8 1.1488 51.68
4.4.3. Measured Result
Return loss
Figure 4.29 Return loss variations with accumulation of dust and water on pentagonal patch
antenna
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
2E+09 2.2E+09 2.4E+09 2.6E+09
S11(d
B)
Frequency
S11(dB)
S11(dB)_with Dust
S11(dB)_Water
S11(dB)_Increased
Water Level
105
As shown in the Figure 4.29 measured result is in agreement with the simulated results. We
also observed that with accumulation of water and dust particles over the patch the
resonance frequency shifts towards lower value.
Table 4.5 Measured parameters of the pentagonal patch antenna
Materials
Resonant
Frequency
(GHz)
% Change in
Resonant
Frequency
Return
Loss
(dB)
Bandwidth
(MHz)
Normal antenna 2.34 0 -22.13 40
With dust
particle 2.32 1 -28.34 45
With water level 2.33 0.4 -27.98 40
Increased water
level 2.3 1.7 -29.17 55
4.5. CONCLUSIONS
Therefore, the effect of dielectric loading of different constant on the behavior of square
and pentagonal patch antenna reveals that dielectric loading do not change only the
resonance frequency but also affects its other parameters; VSWR, return loss, gain,
directivity and bandwidth. In particular, the resonance frequency lowers to; 2.26 GHz, 2.24
GHz, and 2.14 GHz for dielectrics of εr= 2.2, 2.5 and 3.02 respectively and corresponding
shift in frequency are found to be 0.24 GHz, 0.26 GHz and 0.36 GHz respectively [5]. That
is dielectric with lowest dielectric constant (εr = 2.2) provide better impedance matching,
hence has nominal effects and do not disturb much the performance characteristics of the
antennas. The obtained results also indicate that return loss and VSWR increases, however
10-dB return loss, BW and directivity decreases with the dielectric constant of dielectrics.
The value of impedance, return loss and VSWR are minimum, whereas BW and directivity
are maximum for dielectric having dielectric constant (εr = 2.2) and vice-versa for εr = 3.02.
The obtained results are found true that low εr material induced less capacitance during
loading on the patch antenna, hence could be preferred to use as protective layers for
106
antenna systems. The antenna performance has also been studied under the different
conditions, accumulating snow, dust, particle and Plexiglas on the antenna and found that:
Accumulation of snow on square microstrip patch antenna reduces the resonant frequency
from 2.45 GHz to 2.3875 GHz. For snow, accumulation is confined to height of 0.1 mm.
This results in 2.55% change in the resonant frequency. Similarly in case of dust particles
and Plexiglas, whereas in dust particle slight change in resonant frequency is observed, it
deviates from 2.45 GHz to 2.425 GHz, with a percentage change of just 1.02%. Plexiglas
affects resonant frequency the most, i.e., from 2.45 GHz to 2.1375 GHz. This leads to a
12.75% change in the resonant frequency. Also, accumulation of snow on pentagonal
microstrip patch antenna doesn‘t affect the resonant frequency. For snow, accumulation is
confined to height of 0.1 mm. Similarly it is considered in case of dust particles and
Plexiglas, where as in dust particle slight change in resonant frequency is observed, it
deviates from 2.4375 GHz to 2.4125 GHz, with a percentage change of just 1.02%.
Plexiglas affects resonant frequency the most, i.e., from 2.4375 GHz to 2.4125 GHz. This
leads to a 1.02 % change in the resonant frequency. The measured results are in agreement
with the simulated results. In order to study the performances of the microstrip antenna
under various temperature variations, the chapter FIVE focuses to describe the effects of
temperature changes on the patch antennas.
107
REFERENCES
1. I. J. Bahl and S. S. Stuchly, ―Analysis of a microstrip covered with a lossy dielectric‖,
IEEE Trans. Microwave Theory Tech. Vol. MTT-28. No.2, pp. 104-109, Feb. 1980.
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