CHAPTER 4
Designing of MSA
The design of RMSA, CMSA and nonlinear MSA is critical at higher frequencies due to
number of factors. It becomes difficult for designer to optimize the parameters for
extraction of best performance of any particular MSA. The process of designing of such
antenna starts with appropriate selection of specific material suitable for fabrication.
Further the designing process has to consider the patch dimensions along with thickness to
optimize the antenna performance parameters such as percentage bandwidth ,return loss ,
bandwidth, VSWR etc. This chapter briefly elaborates the fundamental concepts of
property of material of substrate, patch platting material and corresponding design
equations with respect to RMSA, CMSA and Nonlinear MSA.
4.1
Properties of Material and Substrate
There are various substrates which can be used for designing and fabrication of MSAs
. The dielectric constant of substrates usually lie in the range of 2.2 to 12. Lower
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Chapter 4. Designing of MSA
the dielectric constant of substrate results better performance of antenna than that of
thicker substrate, because they provide better efficiency and larger bandwidth.
Table 4.1 shows various substrates with important electrical properties. In research
work the substrate materials used such as FR4 Glass Epoxy, Paper Epoxy and ROGERS
RO4350B while platting materials used such as Gold, Hal and Nickel[50].
Table 4.1: Electrical properties of commonly used substrate materials for MSAs
Material
Relative
Relative
Permittivity
Bulk
Loss
Conductivity
tangent
(simens/m)
Permeability
(Dielectric
Constant)
Dielectric
µr
(tanδ )
r
FR4 Glass Epoxy
4.4
1
0.02
0
Paper Epoxy
4.4
1
0.04
0
ROGERS RO4350B
3.66
1
0.004
0
Gold
1
0.99996
0
41 ×106
Hal
3.3
1
0.003
0
Nickel
1
600
0
145 ×105
Duroid
2.20
1
0.0009
0
Alumina96 pct
9.40
1
0.006
0
Arlon AR450
4.5
1
0.0026
0
4.2
Design Consideration of RMSA
Effective dielectric constant
[
ref f
=
r+1
2
]
[
+
2
where
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1
][
1+12h
w
]1
2
(4.1)
Chapter 4. Designing of MSA
ref f
r
= Effective Dielectric Constant,
= Dielectric Constant of the substrate,
h=,Heightofthesubstrateand
w=,Widthofthepatch.
Length of the patch
L≈ 0.49λ
d
= 0√ 49λ
r
(4.2)
where
λ =Wavelengthoffreespaceand
r
= Dielectric Constant of the substrate.
Effective length of patch
c
Lef f = 2f0√
(4.3)
ref f
where
c=Velocityoflight,
f0 =resonating frequency and
L=Actualpatchlength.
In Equation 4.3 the resonating frequency f0 is given by:
f0 =
[
2√
][(
c
L
ref
f
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98
)2
(
)2]
n
+ (4.4)
w
Chapter 4. Designing of MSA
where
m and n = Operating mode parameters and
L=Patchlengthw=Patchwidth
Change in dimension of length due to fringing field
[
][w
]
( ref f + 0.3)
h +0.264
Δ L = 0.412h
w
( ref f − 0.258)
h +0.8
(4.5)
where
w=Patchwidth,
h=Heightofthesubstrateand
ref f
= Effective Dielectric Constant.
Width of patch
The Mathematical equations for length and width are as follows:
Lg = 6h + L
(4.6)
Wg = 6h + w
(4.7)
where
w=Patchwidth,
h=Heightofthesubstrateand
L=Actualpatchlength.
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Chapter 4. Designing of MSA
4.3
Design Consideration of CMSA
General View of Circular MSA is as shown in Figure 4.1. The design of CMSA
is critical at higher frequencies due to number of factors. For example conventional
CMSA at lower frequencies uses thin substrate and generally has narrow bandwidth
performance.
Figure 4.1: General View of Circular Microstrip Antenna
The resonance frequency of a CMSA is obtained using the formula:
f0 = 2π ae√
e
where
Kmn = mth root of the derivative of the Bessel function of order,
C=velocityoflight,
ae = effective radius and
e
= effective dielectric constant.
Actual radius of the circular patch is given by:
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(4.8)
Chapter 4. Designing of MSA
a= √
1+
2hFπ
r
F
[ (π F)
ln 2h + 1.7726
]
(4.9)
where
h=heightofsubstrate,
r
= dielectric constant.
The value of F is calculated as:
F = 8.7√ 1×109
er fr
(4.10)
Effective radius of the circular patch is given by equation
ae = a
{
1+
[ ( π a)
]} 2
2h ln
+ 1.7726
πa r
2h
(4.11)
One method of improving the bandwidth is to use thicker substrate. Therefore, as
these substrates would be electrically thick at higher frequencies, one would expect a
higher bandwidth, but at the same time the losses would increase and hence must be
compensated. In addition as substrate thickness increased, higher order surface wave
mode may propagate.[54]
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Chapter 4. Designing of MSA
4.4
Design Consideration of NLMSA
In research work nonlinear MSA has been design using FR4 Glass epoxy, paper epoxy
and ROGERS RO4350B as a substrate material similarly Gold, Hal and Nickel can
be used as a platting material. These nonlinear MSA’s are simulated by HFSS and
fabricated. It is possible to design and fabricated various shapes and sizes of MSA
(Nonlinear MSA) such as diamond, leaves of flower or tree. In research work RMSA is
modified into nonlinear MSA by making residual change at one corner of RMSA. This
change has been made at any one corner of RMSA. In this work Nonlinear equations,
HFSS will generate automatically equations for designing NLMSA in the process of
simulation[55, 56].
4.5
Design Methodology
General View of Design Methodology is as shown in Figure 4.2.
Figure 4.2: General View of Design Methodhodology
The design of MSA is critical at higher frequencies due to number of factors. One
cannot start fabricating MSA because if the design gets failed the entire cost of
fabrication cost and time is going to be waste. Therefore, simulation and testing prototype
MSA is essential to reduce the cost of overall design and manufacturing.
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Chapter 4. Designing of MSA
The design process has three basic phases:
1. Select type of MSA : RMSA, CMSA or NLMSA.
2. Select type of variations: Substrate Thickness, Substrate Material or Patch
platting Material.
3. Select Testing Method in Sequence: HFSS Simulation, VNA testing of
fabricated MSA and AMS testing for real time practical validation of MSA.
The output as shown in Figure 4.2 will be either MSA simulation results of HFSS or
MSA fabricate measured results of VNA or MSA radiation profile results of AMS.
4.5.1
Design with Substrate Thickness Variation
In research work simulation and fabrication design of MSA can be carried out for
Rectangular, Circular and Nonlinear MSA. For these design the substrate material
used is FR4 Glass epoxy with substrate thickness 0.2 mm, 0.8 mm and 1.6 mm[57].
Table 4.2 shows Substrate Thickness Variation with 0.2 mm, 0.8 mm, 1.6 mm, Glass
Epoxy.
Table 4.2: Substrate Thickness Variation
MSA Shape
Substrate
Substrate
Substrate
Thickness(mm)
Thickness(mm)
Thickness(mm)
Rectangular
0.2
0.8
1.6
Circular
0.2
0.8
1.6
Non-Linear
0.2
0.8
1.6
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Chapter 4. Designing of MSA
4.5.2
Design with Substrate Material Variation
In research work simulation and fabrication design of MSA can be carried out for
Rectangular, Circular and Nonlinear MSA. For these design the substrate material are
used as is FR4 Glass epoxy, Paper Epoxy and ROGERS RO4350B with substrate
thickness 1.6 mm[58]. Table 4.3 shows Substrate Material Variation with Glass Epoxy,
Paper Epoxy, ROGERS substrate of 1.6 mm
Table 4.3: Substrate Material Variation
MSA Shape
Substrate Material
Substrate Material
Substrate Material
Rectangular
Glass Epoxy
Paper Epoxy
ROGERS
Circular
Glass Epoxy
Paper Epoxy
ROGERS
Non-Linear
Glass Epoxy
Paper Epoxy
ROGERS
4.5.3
Design with Platting Variation
In research work simulation and fabrication design of MSA can be carried out for
Rectangular, Circular and Nonlinear MSA. For these design the platting materials are
used as Gold, Hal and Nickel with substrate thickness 1.6 mm. basically, these platting
materials are coated on copper patch FR4 Glass Epoxy.
Table 4.4 shows Patch platting Material Variation with Gold, Hal, Nickel as platting
material. This platting material is coated on patch of conducting material where the
patch was on substrate material.
4.6
Design Analysis Methodology
Simulation, fabrication and analysis of radiation pattern of MSAs have been elaborated
in Chapter 5, Chapter 6 and Chapter 7 respectively. All these subsequent chapter
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Chapter 4. Designing of MSA
Table 4.4: Substrate Platting Variation
MSA Shape
Platting Material
Platting Material
Platting Material
Rectangular
Gold
Hal
Nickel
Circular
Gold
Hal
Nickel
Non-Linear
Gold
Hal
Nickel
comparison of substrate thickness variations, substrate material variations and patch
platting variations are consolidated to give the truthfulness of design with respect to
substrate antenna parameters and antenna profile patterns. Graphical presentation of
analysis of various MSA parameters explained in Chapter 5, Chapter 6 and Chapter
7 gives pictorial view of overall design process and therefore it becomes easier for the
designer to identify the best MSA performance. Apparently designer has to select the
MSA substrate material, its thickness and patch platting material depending upon
application and constraint of cost while fabricating them. However, designer may have look
on various options available during the simulation analysis and make a decision before
he or she goes for actual manufacturing the specific MSA.
The main focus of the work carried out and presented in this thesis emphasizes designing
of substrate thickness variation, material and patch platting variations particularly for
rectangular (RMSA), circular (CMSA) and nonlinear (NLMSA) microstrip antennas has
been briefed in this chapter. Next subsequent chapters (5, 6 and 7) are dealing with
simulation, fabrication and implementation respectively.
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