Microstrip Antenna Resonating at Ku-band frequency Report

MICROSTRIP PATCH ANTENNA RESONATING AT Ku-BAND
DEPARTMENT OF ELECTRONIC SCIENCE, BUB 1
ABSTRACT
Microstrip antenna is an electrical antenna which consists of a metallic patch on a grounded
substrate. Microstrip antennas were primarily used for space borne applications which uses
frequencies of the microwave range. The main objective of this project is to design and characterize
Rectangular Microstrip antenna to operate at Ku-band frequency of 15GHz. In this project,
aRectangular Microstrip antenna resonating at 15GHz frequency has been designed and
characterized using HFSS(High Frequency Structural Simulator) software. The parameters of the
antenna like the bandwidth, radiation pattern, and return loss have been found out using the HFSS
software[1].
The specific frequency chosen here is used for space communications, radar applications, amateur
radio, other terrestrial communications and networking. Microstrip antenna at this frequency ranges
are of great importance nowadays wherein the dimensions of the patch, transmission line and the
feed becomes very small. Considerable effort has beentaken to optimize the width and length of the
conducting patch and the feed. It has taken quite a lot of time in designing to get 50Ω impedance at
the port-feed contact in order to get the power transferred to the conducting patch which is an
essential requirement for proper radiation of the antenna[1].

CHAPTER-1
INTRODUCTION TO ANTENNAS
Antennas

1.1 History of antenna
James Clerk Maxwell formulates the mathematical model of electromagnetism (classical
electro-dynamics), “A Treatise on Electricity and Magnetism”, 1873.He shows that light is an
electromagnetic (EM) wave, and that all EM waves propagate through space with the same
speed, the speed of light.
Heinrich Rudolph Hertz demonstrates in 1886 the first wireless EM wave system: a /2λ-dipole is
excited with a spark; it radiates predominantly at λ≈8 m; a spark appears in the gap of a receiving
loop some 20 m away. In 1890, he publishes his memoirs on electrodynamics, replacing all
potentials by field strengths.
May 7, 1895, a telegraph communication link is demonstrated by the Russian scientist, Alexander
Popov. A message is sent from a Russian Navy ship 30 miles out in sea, all the way to his lab in St.
Petersburg, Russia. This accomplishment is little known today.
In 1892, Tesla delivers a presentation at the IRE of London about “transmitting intelligence
without wires,” and, in 1895, he transmits signals detected 80 km away. His patent on wireless
links precedes that of Marconi.
Guglielmo Marconi sends signals over large distances and successfully commercializes wireless
Communication systems. In 1901, he performs the first transatlantic transmission from Poldhu in
Cornwall, England, to Newfoundland, Canada. He receives the Nobel Prize for his work in 1909.
The beginning of 20th century (until WW2) marks the boom in wire-antenna technology (dipoles
and loops) and in wireless technology as a whole, which is largely due to the invention of the
DeForest triode tube, used as radio-frequency (RF) generator. Radio links are realized up to UHF
(about 500 MHz) and over thousands of kilometers.
WW2 marks a new era in wireless communications and antenna technology. The invention of
new microwave generators (magnetron and klystron) leads to the development of the
microwave antennas such as waveguide apertures, horns, reflectors, etc.
1.2 Introduction
An antenna or aerial is defined as “A means for radiating or receiving radio waves”. In other words
the antenna is the transitional structure between free space and a guiding device, the guiding device

or transmission line may take the form of a coaxial line or a hollow pipe (waveguide) and it is used to
transfer electromagnetic energy from the transmitting source to antenna or from the antenna to
receiver.
Antennas are basic components of any electric system and are connecting links between the
transmitted and free space or free space and the receiver. Thus antennas play very important role in
finding the characteristics of the system in which antennas are employed. Antennas are employed in
different systems in different forms. That is in some system the operational characteristics of the
system are designed around the directional properties of the antennas or in some others systems,
the antennas are used simply to radiate electromagnetic energy in an omnidirectional or finally in
some systems for point –to- point communication purpose in which increased gain and reduced
wave interference are required.
Transmission and Reception of Antenna
A guided wave traveling along a transmission line, which opens out as in figure 1.2, will radiate as
free space wave. The guided wave is a plane wave while the free space wave is a spherically
expanding wave. Along the uniform part of the line, energy is guided, as a plane wave with little loss,
provided the spacing between the wires is a small fraction of a wavelength. At the right, as the
transmission line separation approaches a wavelength or more, the wave tends to be radiated so
that the opened-out line acts like an antenna, which launched the free space wave. The currents on
the transmission line flow out on the transmission line and end there, but the fields associated with
them keep on going. To be more explicit, the region of transition between the guided wave and the
free space wave may be defined as an antenna.

Figure1.2 Antenna as Transmission device
In this vast and dynamic field, the antenna technology has been an indispensable partner of the
communication revolution. Many major advances that took place over the years are now in common
use. Despite numerous challenges, the antenna technology has grown with a fast pace to harass the
electromagnetic spectrum, which is one of the greatest gifts of nature.
1.3 Types of antennas
Various forms of antennas have been developed in last few decades. There has been a vigorous and
dynamic change in the field of antennas, which has been an indispensable partner of the
communications revolution. The various forms of antennas are.
a) Wire Antennas
b) Aperture Antennas
c) Microstrip Antenna
d) Array Antennas
e) Reflector Antennas
f) Lens Antennas

Though there are different types of antennas available, we have selected the microstrip
antenna..Since Microstrip antennas became very popular in the 1970s primarily for space borne
applications. Today they are used for government and commercial applications. These antennas
consist of a metallic patch on a grounded substrate. The metallic patch can take many different
configurations. However, the rectangular and circular patches, shown in Figure 1.3, are the most
popular because of ease of analysis and fabrication, and their attractive radiation characteristics,
especially low cross-polarization radiation.
Rectangular Patch
Circular Patch
Figure1.3 Typical Microstrip Antenna

1.4 Radiation mechanism of Antennas
Radiation mechanism of antennas clearly explains “how the Radiation accomplished?” In other
words, how are the electromagnetic fields generated by the source, contained and guided within the
transmission line and antenna, and finally “detached” from the antenna to form a free-space wave?
These can be illustrated by examining some basic sources of radiation.
1.4.1 Radiation Mechanism in Single Wire
The fundamental relation of electromagnetic radiation simply states that to create radiations, there
must be a time-varying current or an acceleration (or deceleration) of charge.
Where, l – Length of the wire (mm)
az– Acceleration (m/ss)
ql- Charge per unit length (c)
We usually refer to currents in time-harmonic applications while charge is most often mentioned in
transients. To create charge acceleration (or deceleration) the wire must be curved, bent,
discontinuous, or terminated. Periodic charge acceleration (or deceleration) or time-varying current
is also created when charge is oscillating in a time-harmonic motion. Therefore:
1. If a charge is not moving, current is not created and there is no radiation.
2. If charge is moving with a uniform velocity:
a. There is no radiation if the wire is straight and infinite in extent.
b. There is radiation if the wire is curved, bent, discontinuous, terminated, or truncated.
3. If charge is oscillating in a time-motion, it radiates even if the wire is straight.
1.4.2 Radiation Mechanism in Two Wires
Let us consider a voltage source connected to a two-conductor transmission line which is connected
to an antenna. This is shown in Figure 1.4.2(a). Applying a voltage across the two-conductor
transmission line creates an electric field between the conductors. The electric field has associated
with it electric lines of force which are tangent to the electric field at each point and their strength is
proportional to the electric field intensity. The electric lines of force have a tendency to act on the
free electrons (easily detachable from the atoms) associated with each conductor and force them to
be displaced. The movement of the charges creates a current that in turn creates magnetic field
intensity. Associated with the magnetic field intensity are magnetic lines of force which are tangent
to the magnetic field.
Magnetic field lines always form closed loops encircling current-carrying conductors because

physically there are no magnetic charges. The electric field lines drawn between the two conductors
help to exhibit the distribution of charge.
Figure 1.4.2
Source,
transmission
line, antenna, and
detachment of
electric field
lines.
W e remove part
o f the antenna
structure, as
shown in
F i g u r e
1 . 4 . 2 ( b ) ,
f r e e - s p a c e
waves can be
formed by
“connecting”
t h e open ends of
t h e electric lines
( s h o w n
dashed).The
f r e e - s p a c e
waves are also
periodic but a
c o n s t a n t
phase point
P 0 m o v e s
o u t w a r d l y
with the speed of light and travels a distance of λ/2 (to P1) in the time of one-half of a period. If the
initial electric disturbance by the source is of a short duration, the created electromagnetic waves
travel inside the transmission line, then into the antenna, and finally are radiated as free-space
waves, even if the electric source has ceased to exist (as was with the water waves and their
generating disturbance).

Figure 1.4.2 Electric field lines of free-space wave for bi-conical antenna.
If the electric disturbance is of a continuous nature, electromagnetic waves exist continuously and
follow in their travel behind the others. This is shown in Figure 1.4.2 (c) for a bi-conical antenna.
When the electromagnetic waves are within the transmission line and antenna, their existence is
associated with the presence of the charges inside the conductors. However, when the waves are
radiated, they form closed loops and there are no charges to sustain their existence. This leads us to
conclude that electric charges are required to excite the fields but are not needed to sustain them
and may exist in their absence.
1.5 Microstrip Antenna
Microstrip patch antennas are the most common form of printed antennas. They are popular for
their low profile, geometry and low cost. A microstrip device in its simplest form is a layered
structure with two parallel conductors separated by a thin dielectric substrate. The lower conductor
acts as a ground plane. The device becomes a radiating microstrip antenna when the upper
conductor is a patch with a length that is an appreciable fraction of a wavelength (λ), approximately
half a wavelength (λ / 2). In other words, a microstrip patch antenna consists of a radiating patch on
one side of a dielectric substrate which has a ground plane on the other side as shown in Fig. 1.5(a).

Figure 1.5(a)– Typical microstrip patch antenna
Microstrip patch antennas radiate primarily because of the fringing fields between the patch edge
and the ground plane. Microstrip patch antennas have many advantages when compared to
conventional antennas. As such, they have found usage in a wide variety of applications ranging
from embedded antennas such as in a cellular phone, pagers etc. to telemetry and communication
antennas on missiles and in satellite communications.
Patch
The patch is generally made of conducting material such as copper or gold and can take any
possible shape.
Some of the typical patch shapes are shown in Fig. 1.5(b).
The radiating patch and the feed lines are usually photo etched on the dielectric substrate.

Figure 1.5(b)– Different shapes and sizes of patch
Substrate Material
The dielectric substrate material of a microstrip patch antenna can be of any type like RT Duriod ,
Quartz, FR4 Epoxy, Silicon etc..,
The Dielectric Substrate Material we are using in our Design is FR4 Epoxy
Where “FR” means Flame Retardant and type 4 indicates Woven Glass reinforced Epoxy
resin.
The Range of the dielectric constant of FR4 Epoxy typically depends on glass resin.
This material is popular and cost effective Compared to other PCB material.
FR4 is most Commonly Used as an electrical insulator possessing considerable mechanical
Strength.
FR4 is also used in the construction of relays, switches, standoffs, busbars, washers,
transformer and screw terminal strips.
Ground Plane
The ground plane is part of the antenna. Ideally, the ground plane should be infinite as for a
microstrip patch antenna. But, in reality, a small ground plane is desirable. The radiation of a
microstrip antenna is generated by the fringing field between the patch and the ground plane, the
minimum size of the ground plane is therefore related to the thickness of the dielectric substrate.
Generally speaking, a λ/4 extension from the edge of the patch is required for the ground plane,
whereas the radius of a monopole ground plane should be at least one wavelength.

Feed Techniques for Patch Antennas
Microstrip antennas are fed by a variety of methods that are broadly classified into two main
categories, namely, contacting and non-contacting. In the contacting method, the RF power is fed
directly to the radiating patch using a connecting element such as a microstrip line. In the
non-contacting method, electromagnetic field coupling is done to transfer power between the
microstrip line and the radiating patch.
The four most popular feed techniques used are the microstrip line, coaxial probe (both contacting
schemes), aperture coupling and proximity coupling (both non-contacting schemes).
a) Microstrip Line Feed
This type of feed technique excitation of the antenna would be by the Microstrip line of the same
substrate as the patch that is here can be considered as an extension to the Microstrip line, and
these both can be fabricated simultaneously. This conducting strip is directly connected to the edge
of the Micro strip patch. , As known the conducting strip is smaller than that of the patch in width.
This type of structure has actually an advantage of feeding the directly done to the same substrate
to yield a planar structure as said above. The coupling between the Microstrip line and the patch is
in the form of the edge or butt-in coupling as shown in the figure. Or it is through a gap between
them.
A Type of Microstrip feed and the corresponding equivalent circuits, Microstrip feed at a radiating
edge
b) Coaxial Feed
The coaxial feed or probe feed is a very common contacting scheme of feeding patch antennas. The
configuration of a coaxial feed is shown in Fig. below. As seen from Fig. 3.8, the inner conductor of

the coaxial connector extends through the dielectric and is soldered to the radiating patch, while the
outer conductor is connected to the ground plane.
Coaxial Feed
The main advantage of this type of feeding scheme is that the feed can be placed at any desired
location inside the patch in order to match with its input impedance. This feed method is easy to
fabricate and has low spurious radiation.
As we are using only probe feed and linefeed techniques in our design, we do not discuss further
about other remaining methods of feeding here.
1.6 RADIATION MECHANISM IN A MICROSTRIP ANTENNA
In microstrip antennas, the radiation is from the periphery of the patch, where the fringing field is
maximum. Portions of the patch act like slots, with respect to the ground plane. The exciting dipole
launches guided modes in the parallel plate region under the patch. The surface current distributions
can be computed on the conducting and dielectric surfaces of the antenna to understand their
behavior. The radiation from microstrip antennas occurs from the fringing fields between the edge
of the microstrip antenna conductor and the ground plane. For a rectangular microstrip antenna
fabricated on thin dielectric substrate and operating in the fundamental mode, there is no field
variation along the width and thickness. The fields vary along the length, with a period of half a
wavelength. The radiation from a microstrip patch is shown in figure 1.6.

Figure 1.6 Radiation on microstrip patch
The radiation mechanism can be explained by resolving the fringing fields at the open
circuited edges into the normal and tangential components with respect to the ground plane. The
normal components are out of phase (as the patch is half wavelength long) and hence the far fields
produced by them cancel each other. The tangential components are in phase and the resulting
fields are combined to give maximum radiation in the broadside direction.

CHAPTER-2
FUNDAMENTAL
PARAMETERS OF
ANTENNAS
parameters of Antennas
2.0 Introduction
The History of a basic antenna, its working, radiation mechanism and its types, microstrip antenna
were outlined in the previous chapter. Here we are discussing about the essential parameters of an
antenna in brief with its formulae.
2.1 Gain

The gain of the antenna is closely related to the directivity. In addition to the directional capabilities
it accounts for the efficiency of the antenna.
Gain does not account for losses arising from impedance mismatches (reflection losses) and
polarization mismatches (losses).Gain is the ratio of the intensity, in a given direction, to the
radiation intensity that would be obtained if the power accepted by the antenna were radiated
isotropically.
Gain = 4π = 4π (dimensionless).
2.2 Efficiency
The total antenna efficiency e0 is used to take into account losses at the
input terminals and within the structure of the antenna.e0 is due to the combination of number of
efficiencies:
е0= er ec ed
Where, е0 = total efficiency,
er = reflection efficiency
ec= conduction efficiency,
ed= dielectric efficiency,
2.3Directivity
Directivity of an antenna is defined as “The ratio of the radiation intensity in a given direction from
the antenna to the radiation intensity averaged over all directions. The average radiation in intensity
is equal to the total power radiated by the antenna divided by 4 . If the direction is not specified,
the direction of maximum radiation intensity is implied.”
The directivity of a non-isotropic source is equal to the ratio of its radiation intensity in a given
direction over that of an isotropic source.
Directivity is defined as
D
If the direction is not specified, It implies the direction of maximum radiation intensity (maximum

directivity) expressed as
Dmax=Do
Where, D=directivity (dimensionless)
Do=maximum directivity (dimensionless)
U=radiation intensity (w/unit solid angle)
Umax=maximum radiation intensity of isotropic source (W/unit solid angle)
Uo=radiation intensity of isotropic source (W/unit solid angle)
Prad=total radiated power (w)
2.4 Bandwidth
Another important parameter of any antenna is the bandwidth it covers. Only impedance bandwidth
is specified most of the time. However, it is important to realize that several definitions of
bandwidth exist impedance bandwidth, directivity bandwidth, polarization bandwidth, and efficiency
bandwidth. Directivity and efficiency are often combined as gain bandwidth.
This is the frequency range wherein the structure has a usable bandwidth compared to a certain
impedance, usually 50Ω.The impedance bandwidth depends on a large number of parameters
related to the patch antenna element itself (e.g., quality factor) and the type of feed used. The plot
below shows the return loss of a patch antenna and indicates the return loss bandwidth at the
desired S11/VSWR (S11 wanted/VSWR wanted). The bandwidth is typically limited to a few percent.
This is the major disadvantage of basic patch antennas.
BW = X 100 %
Where, fH = upper cut-off frequency (GHz)
fL = lower cut-off frequency (GHz) and
fc = centre frequency(GHz)

2.5 Radiation Pattern
An antenna radiation pattern or antenna pattern is defined as “a mathematical function or a
graphical representation of the radiation properties of the antenna as a function of space
coordinates. In most cases, the radiation pattern is determined in the far field region and is
represented as a function of the directional coordinates. Radiation properties include power flux
density, radiation intensity, field strength, directivity, phase or polarization.”
Various parts of a radiation pattern are referred to as lobes, which may be sub classified into major
or main, minor, side, and back lobes.
A radiation lobe is a “portion of the radiation pattern bounded by regions of
relatively weak radiation intensity.” Figure 2.5(a) demonstrates a symmetrical three dimensional
polar pattern with a number of radiation lobes. Some are of greater radiation intensity than others,
but all are classified as lobes. Figure 2.5(b) illustrates

Figure2.5(a) Radiation lobes and beamwidth of an antenna pattern.
Figure2.5(b) Linear plot of power pattern and its associated lobes and beamwidth.
i) Major Lobe: A major lobe (also called main beam) is defined as “the radiation lobe containing the
direction of maximum radiation.” In Figure 2.5(b) the major lobe is pointing in the θ= 0 direction. In
some antennas, such as split-beam antennas, there may exist more than one major lobe.
ii) Minor Lobe: A minor lobe is any lobe except a major lobe. In Figures 2.5(a) and (b) all the lobes
with the exception of the major can be classified as minor lobes.
iii) Side Lobe: A side lobe is “a radiation lobe in any direction other than the intended lobe.” (Usually
side lobe is adjacent to the main lobe and occupies the hemisphere in the direction of the main
beam.)
iv) Back Lobe: A back lobe is “a radiation lobe whose axis makes an angle of approximately 180◦ with
respect to the beam of an antenna.” Usually it refers to a minor lobe that occupies the hemisphere
in a direction opposite to that of the major lobe.

2.6 Beamwidth
• The beamwidth of an antenna is a very important figure of merit and often is used as a trade-off
between it and the side lobe level; that is, as the beamwidth decreases, the side lobe increases and
vice versa.
• The beamwidth of the antenna is also used to describe the resolution capabilities of the antenna
to distinguish between two adjacent radiating sources or radar targets.
Half-Power Beamwidth (HPBW)-In a plane containing the direction of the maximum of a beam, the
angle between the two directions in which the radiation intensity is one-half value of the beam.
First-Null Beamwidth (FNBW)- Angular separation between the first nulls of the pattern.
Beamwidth of an Antenna
Resolution
• The most common resolution criterion states that the resolution capability of an antenna to
distinguish between two sources is equal to half the first-null beamwidth (FNBW/2), which is usually
used to approximate the HPBW.
• That is, two sources separated by angular distances equal or greater than FNBW/2 ¼ HPBW of an
antenna with a uniform distribution can be resolved.
• If the separation is smaller, then the antenna will tend to smooth the angular separation distance.

2.7 Polarization
The polarization of an antenna is the polarization of the wave radiated from the antenna. A receiving
antenna has to be in the same polarization as the transmitting antenna otherwise it will not
resonate. Polarization is a property of the electromagnetic wave. It describes the magnitude and
direction of the electric field vector as a function of time, with other words “the orientation of the
electric field for a given position in space”. A simple strait wire has one polarization when mounted
vertically, and different polarization when mounted horizontally figure2.7. Polarization can be
classified as linear, circular, and elliptical.
In linear polarization the antenna radiates power in the plane of propagation, only one plane, the
antenna is vertically linear polarized when the electric field is perpendicular to the earth’s surface,
and horizontally linear polarized when the electric field is parallel to the earth’s surface. Circular
polarization antenna radiates power in all planes in the direction of propagation (vertical, horizontal,
and between them). The plane of propagation rotates in circle making one complete cycle in one
period of wave.
Figure 2.7 - Polarization of electromagnetic wave
2.8 VSWR (Voltage Standing Wave Ratio)
The VSWR (also known as the standing wave ratio, SWR) is defined as the ratio of the magnitude of
the maximum voltage on the line to the magnitude of the minimum voltage on the line, as shown in
Figure Below. Mathematically, it can be expressed as
VSWR ( )
The VSWR is just another measure of how well a transmission line is matched with its load. Unlike
the reflection coefficient, the VSWR is a scalar and has no phase information. For a non perfect

transmission line, the VSWR is a function of the length of the line ( ) as well as the load impedance
and the characteristic impedance of the line. But for a lossless transmission line, the VSWR is the
same at any reference point of the line.
Return loss as a function of the line length
2.9 Return loss
The bandwidth of an antenna over which the return loss is acceptable is directly proportional to the
volume the antenna occupies, so very small antennas can produce inadequate bandwidth, especially
in the 850 MHz band where the effective volume is smallest relative to the frequency of operation.
The efficiency of a typical embedded antenna can range from about 40 to 75%. Greater than 75%
efficiency is challenging to obtain from a fully embedded antenna and lower than 40% efficiency will
typically cause certification failures. In most cases, the efficiency goal should be 60%, with 40% as an
absolute minimum. It is important to understand that good return-loss performance can be
inadvertently achieved at the expense of efficiency. An extreme example of this concept is a 50 ohm
resistor: the resistor has an excellent return loss but has virtually 0% efficiency, and is obviously not
an antenna. Therefore, an understanding of the return loss and efficiency concepts is critical to good
antenna design.
RL (dB) = 10 log(Pi/Pr)
Where, RL (dB) - Return Loss in dB
Pi – Incident Power (w)
Pr – Reflected Power (w)
Return Loss is related to both standing wave ratio (SWR) and reflection coefficient (Г). Increasing

return loss corresponds to low SWR. Return loss is measure of how well devices or lines are
matched. A match is good if the return loss is high. A high return loss is desirable and results in a
lower insertion loss.
12.10 Input Impedance
The input impedance of an antenna is defined as “the impedance presented by an antenna at its
terminals or the ratio of the voltage to the current at the pair of terminals or the ratio of the
appropriate components of the electric to magnetic fields at a point”. Hence the impedance of the
antenna can be written as given below.
Zin = Rin + jXin (Ω)
Where, Zin is the antenna impedance at the terminals
Rin is the antenna resistance at the terminals
Xin is the antenna reactance at the terminals
The imaginary part, Xin of the input impedance represents the power stored in the near field of the
antenna. The resistive part, Rin of the input impedance consists of two components, the radiation
resistance Rr and the loss resistance RL. The power associated with the radiation resistance is the
power actually radiated by the antenna, while the power dissipated in the loss resistance is lost as
heat in the antenna itself due to dielectric or conducting losses.
If we assume that the antenna is attached to a generator with internal impedance
Zg = Rg + jXg (Ω)
Where, Rg is the resistance of generator impedance.
Xg is the reactance of generator impedance.
2.11 Effective Aperture
The effective aperture Aw is a parameter that is defined especially for receiving antennas. It is a
measure of the maximum received power Pr which the antenna can obtain from a plane wave of
power density S:
Prmax = S . Aw (w)
Although the effective aperture can definitely be thought of as a real aperture that is perpendicular
to the direction of propagation of the incident wave, it is not necessarily identical to the geometric
aperture Ag of the antenna. The relationship between the two apertures is described by the

aperture efficiency
q = Aw / Ag (c)
The effective aperture and the gain can be converted from one to the other with the aid of the
equation:
Aw

CHAPTETR - 3
DESIGN OF MICROSTRIP
ANTENNA
Designing of Microstrip Antenna
3.0 Introduction
The discussion on basic antenna, Its types, Radiation mechanism, Study of microstrip antenna,
Fundamental parameters of antennas were outlined in the previous chapters. In this chapter we are
discussing about the design specifications, Software tool required to design a microstrip patch
antenna.
3.1 Design Specifications
The three essential parameters for the design of a rectangular Microstrip Patch Antenna are:

Frequency of operation (fr): The resonant frequency of the antenna must be selected
according to our applications. We use the resonating frequency as 22 GHz for our design.
Dielectric constant of the substrate (εr): Glass Epoxy is used in our design with dielectric
constant of 4.4.
Height of dielectric substrate (h): Height of dielectric substrate controls the bandwidth. The
value of h used in our design is 1.6mm.
Step 1: Width of Patch
The width of the patch element (W) is given by
W (mm)
Where, C is the speed of light(c= 3 x m/s)
is the resonant frequency
is the dielectric constant of the substrate
Step 2: Effective Dielectric Constant
The effective dielectric constant (εeff) is an important parameter which arises because part of the
fields from the microstrip conductor, exist in air. It is calculated as
Ԑreff

Step 3: Effective Length
The effective length (Leff) is given
Leff (mm)
Step 4: Length Extension
Because of the fringing effects, electrically the patch of the antenna looks larger than its physical
dimensions. Thus length extension (∆L) is given by
∆L (mm)
Step 5: Length of Patch
The actual length (L) of patch is obtained by
L=Leff - 2∆L (mm)
Step 6 : Length, Width of Ground Plane
Calculation of the ground plane Lg and Wg: Usually the size of the ground plane is greater than the
patch dimension by approximately six times the substrate thickness all around the periphery
Lg= 6h + L (mm)
And,
Wg = 6h + W (mm)
Step 7 : Length of the feed
The Length of the feed
Lf (mm)

Where λg = c / fr (m)
Step 8 : Width of the feed
The width of the feed (Wf) is given by
for < 2 (mm)
Where,
A (mm2)
For example :
If fr = 22GHz,εr=4.4, h=1.6mm
C=
The width of the patch element
W
W
W
W = 4.14mm
Effective Dielectric Constant
Ԑreff
Ԑreff
Ԑreff

Ԑreff 2.805
Effective Length
Leff
Leff
Length Extension
∆L
∆L
∆L
Length of Patch
L = – (2 x
L =
Length of Ground Plane
Lg = 6 x 1.6 +
Lg = 12.33mm
Wg = 6 x 1.6 +
Wg = 9.6 +

Wg = 13.74mm
Lf
Lf
Lf
λg = 3 x 108 / 22 x 109
λg = 0.3 x 109 / 22 x 109
λg = 0.0136 (m)
Wf x
Wf
A
A
A = 0.834 x 1.7624
A = 1.4697 (mm2)
3.2 Software Tool Used: HFSS
In order to design a microstrip rectangular patch antenna to operate in a Ku band frequency range,
Although there are various simulation software available for example FEKO, IE3D, HFSS, CST…, etc.
We are using HFSS (High Frequency Structural Simulator) to design a MSA. It is more commonly used
software because of its friendly user interface and better accuracy for complicated geometries.
Therefore, in the present work, we have used HFSS Version 13.0

HFSS software is considered the industry standard for 3D electromagnetic structure simulator. It is
considered as an essential tool for high speed and high frequency component designs. HFSS offers
solver technologies based on either integral equation method or finite element method.
HFSS solver is equipped with automated solution methods so all we need to do is to specify the
geometry, the properties of material and output. From here onwards HFSS will take charge and will
generate a mesh for solving the problem.
Ansoft HFSS can be used to calculate parameters such as S-Parameters, Resonant Frequency, and
Fields. Typical uses include:
Package Modeling – BGA, QFP, Flip-Chip
PCB Board Modeling – Power/ Ground planes, Mesh Grid Grounds, Backplanes
Silicon/GaAs-Spiral Inductors, Transformers EMC/EMI – Mobile Communications –
Patches, Dipoles, Horns, Conformal Cell Phone Antennas, Quadrafilar Helix, Specific
Absorption Rate ( SAR), Infinite Arrays, Radar Section (RCS), Frequency Selective Surface
(FSS) Connectors – Coax, SFP/XFP, Backplane, Transitions
Waveguide – Filters, Resonators, Transitions, Couplers
Filters – Cavity Filters, Microstrip, Dielectric
Features of HFSS Software
High speed, High Frequency component modeling.
Solver Technologies are based on several methods.
Can select the appropriate method amongst integral equation method or finite element method.
Equipped with automated solution methods.
Automatic Adaptive Meshing
Advanced Finite Array Simulation Technology
Mesh Element Technologies
Advanced Broadband SPICE Model Generation
Optimization and Statistical Analysis
EDA Design Flow Integration
High-Performance Computing
Powerful Post-Processing Capabilities

CHAPTER-4

RESULTS AND
DISCUSSIONS
RESULTS AND DISCUSSIONS
4.0 Introduction
The Microstrip patch antenna is designed to resonate at ku-band (12-18 GHz) using HFSS Software
tool and fabricated on FR4 Epoxy Substrate Material, The design and fabricated results obtained are
discussed in this chapter.
4.1 Simulation of 15 GHZ Patch Antenna
The project is based on designing a microstrip antenna using edge feed technique which resonates
at 15GHz and then vary the parameters of the antenna such that the working of the patch is
optimized. Simulations are divided into three basic groups:
1) To start with, the length of the transmission line is varied. The gain of the antenna varies greatly
as we vary the feed point. We get best gain when the transmission line is located at the 50Ω
impedance line. In this case the return loss curve dips the maximum.
2) The dimensions of the wave port are varied in order to match the impedance to 50Ω.

3) The dielectric substrates are changed and its effects on the performance of the patch are
observed.
All the dimensions of patches are calculated with help of equations given previously. The simulation
results for the patches are given in the following sections.
4.2 Design of MSA with FR4 Epoxy Substrate Material
Height of substrate = 1.6 mm
Dielectric constant = 4.4
Length of ground plane = 30 mm
Width of ground plane = 30 mm
Length of the patch = 3.7 mm
Width of the patch = 5.8 mm
Length of Feed =13.15 mm
Width of Feed =1.5 mm
Frequency = 15.00 GHz
FR4 Epoxy Model (as designed using HFSS)

Figure 4.1: Structural design of MSA
The structural design of Microstrip rectangular patch antenna is as shown in Figure 4.1 and
simulated to resonate at 15GHz of frequency. It can be seen from figure 4.2 that the gain of the MSA
is found to be 5.289dB. The impedance bandwidth over return loss less than -10dB is measured from
12 to 18 GHz of frequency. The variation of return loss versus frequency is shown in figure 4.3.
From figure 4.3 it is seen that the antenna resonates at 15.240 GHz of frequency, with minimum
return loss of -18.193 dB. It can be seen from figure that lower cut-off frequency (fL) is 14.730 GHz,
upper cut-off frequency (fH) is 15.840 GHz and CENTRE frequency (fC) is 15.240 GHz. As given in
sectio n 2.4 the impedance bandwidth (BW) of MSA is found to be BW=7.283%. Though it was
designed to resonate at 15 GHz, but from the frequency response it is resonating at 15.240 GHz
which is very close to the expected value.
Gain Plot

Figure 4.2: Gain Plot of MSA
Return Loss Curve
Figure 4.3: Variation of Return loss versus Frequency

Radiation Pattern
Figure 4.4: Radiation Pattern of MSA
3D Polar Plot

Figure 4.5: 3D Polar Plot of MSA
4.3 MEASUREMENT RESULTS
Fabricated Design of MSA
Figure 4.3(a): Fabricated Microstrip Patch Antenna (Ku - Band)
The Fabricated design of Microstrip rectangular patch antenna is as shown in Figure 4.3(a) and
simulated to resonate at 15GHz of frequency. The impedance bandwidth over return loss less than
-10dB is measured from 12 to 18 GHz of frequency. The variation of return loss versus frequency and
VSWR versus frequency as shown in figure below.
Radiation Plot

VSWR Plot
Far Field Amplitude of MSA

Figure 4.3(b):
Far Field
Amplitude Radiation
Pattern
The Far Field Amplitude Radiation Pattern of an Microstrip Patch Antenna is as shown in the figure
4.3(b).This graph shows the narrow bandwidth and Theta is taken as 90o
Far-field Cut Analysis:
Avg value: -14.035 dB
-3. dB beam width: 38.934 deg, Peak from 3dB pts: -44.1744 deg
4.4 DISCUSSIONS ON SIMULATION RESULTS
Based on the simulation results the effect of changing h and εr on antenna dimensions and
performance is observed. The results are presented in table below assuming a fixed frequency of
operation (15 GHz).
Parameter
variation
Length of the
ground
plane(Lg)
Width of the
ground
plane(Wg)
Length of the
patch(Lp)
Width of the
patch(Wp)
h increased Increases Increases Increases Remains

constant
h decreased Decreases Decreases Decreases Remains
constant
εr increased Decreases Decreases Decreases Decreases
εr decreased Increases Increases Increases Increases
Table 4: Effect of variation of h and εr on patch dimensions
cHAPTER – 5
ADVANTAGES,

DISADVANTAGES AND
APPLICATION OF MSA
ADVANTAGES, DISADVANTAGES AND APPLICATION OF MSA
5.1 Advantages and Disadvantages of Microstrip Patch Antenna
Microstrip Patch Antenna has number of advantages compared to other antennas. Some of their
major advantages are given below
Low Weight
Low Profile
Low Fabrication cost. Hence can be manufactured in large quantities.
Required no cavity backing.
Supports both linear and circular polarization.
Capable of dual and triple frequency operation range.

Feed lines and matching networks can be fabricated simultaneously.
A Single patch antenna provides a maximum directive gain of around 6-9dBi.
Some of their disadvantages are given below
Low Efficiency
Low Gain
Large ohmic Loss in feed structure
Low Power Handling Capacity.
Excitation of surface waves.
Polarization Purity is difficult to achieve.
Complex feed structures require high performance arrays.
5.2 Applications
Microstrip patch antenna has wide range of application some of major applications are given below
Mobile and satellite communication System
Global Positioning System(GPS)
Direct Broad Cast Television(DBS)
Radio Frequency Identification (RFID)
Worldwide Interoperability for Microwave Access (WiMax)
Wireless Local Area Network’s

cHAPTER - 6
CONCLUSIONS
AND FUTURE
SUGGESTIONS

6.1 CONCLUSIONS
The rectangular microstrip antennas (RMSA) were successfully designed, simulated and
characterized using HFSS software for X-band frequency of 15GHz for substrates of varying height (h)
and permittivity (εr).
Substrate
Material
Relative
Permittivity
(εr)
Height In
mm
(h)
Resonating
Frequency
(GHz)
Bandwidth
(GHz)
Gain
(dB)
Return
Loss(dB)
FR4 Glass
Epoxy
4.4 1.6 15.240 0.7283 5.289 -18.193
The above table gives resonating frequency (fr), bandwidth, gain and return loss of the designed
RMSA for different substrates.
In earlier literatures this antenna was designed using inset feed techniques whereas in this project
we have used the edge feed technique which comprises of a quarter wave transformer to match the
impedance. Very few literatures show the use of edge feed most of which operates at C-band
frequencies (4-8GHz) of microwaves.
In this project we have improved the gain of the RMSA. It is found that the obtained frequency (fr) is
≈15GHz. High return loss indicating a good matching.
6.2 FUTURE SUGGESTIONS
It is very important to choose the appropriate substrate for your microstrip antenna design. As said
in this project different substrates affect the performance of the antenna. Proper position to
terminate the Feed line also affects the performance of the antenna. The performance of the
microstrip antenna with substrate- FR4 (glass epoxy) is shown in this project work, Further this
antenna can be designed with other substrate materials like RT-Duroid, Quartz, Silicon etc..,
In this project only transmission line feed technique is used. In future other different type of feed
techniques can be used to calculate the overall performance of the antenna. Further, work can be
done by focusing on the area of different design methods especially in enhancing the impedance,
bandwidth, and the efficiency.

APPENDIX

APPENDIX I
Substrate Material Used:
FR4 Epoxy
FR-4 (or FR4) is a grade designation assigned to glass-reinforced epoxy laminate sheets, tubes, rods
and printed circuit boards (PCB). FR-4 is a composite material composed of woven fiber glass cloth
with an epoxy resin binder that is flame resistant (self-extinguishing).
FR-4 glass epoxy is a popular and versatile high-pressure thermoset plastic laminate grade with good
strength to weight ratios. With near zero water absorption, FR-4 is most commonly used as an
electrical insulator possessing considerable mechanical strength. The material is known to retain its
high mechanical values and electrical insulating qualities in both dry and humid conditions. These
attributes, along with good fabrication characteristics, lend utility to this grade for a wide variety of
electrical and mechanical applications.
Applications
Printed circuit boards
FR-4 is the primary insulating backbone upon which the vast majority of rigid printed circuit
boards (PCBs) are produced. A thin layer of copper foil is laminated to one, or both sides of an FR-4
glass epoxy panel. These are commonly referred to as "copper clad laminates."
FR-4 copper-clad sheets are fabricated with circuitry etched into copper layers to produce printed
circuit boards. More sophisticated and complex FR-4 printed circuit boards are produced in multiple
layers, also known as "multilayer circuitry".
FR-4 is also used in the construction of relays, switches, standoffs, busbars, washers, arc shields,
transformers and screw terminal strips.
Properties
Typical physical and electrical properties of FR-4 are as follows. LW (length wise, warp yarn direction)
and CW (cross wise, fill yarn direction) refer to the fiber orientations in the plane of the board
(in-plane) that are perpendicular to one another. The through-plane direction is also referred to as
the z-axis.

Parameter Value
Speciﬁc gravity/density 1,850 kg/m3 (3,120 lb/cu yd)
Water absorption −0.125 in < 0.10%
Temperature index 140 °C (284 °F)
Thermal conductivity, through-plane 0.29 W/m·K, 0.343 W/m·K
Thermal conductivity, in-plane 0.81 W/m·K, 1.059 W/m·K
Rockwell hardness 110 M scale
Bond strength > 1,000 kg (2,200 lb)
Flexural strength (A; 0.125 in) – LW > 440 MPa (64,000 psi)
Flexural strength (A; 0.125 in) – CW > 345 MPa (50,000 psi)
Tensile strength (0.125 in) LW > 310 MPa (45,000 psi)
Izod impact strength – LW > 54 J/m (10 ft·lb/in)
Izod impact strength – CW > 44 J/m (8 ft·lb/in)
Compressive strength – flat wise > 415 MPa (60,200 psi)
Dielectric breakdown (A) > 50 kV
Dielectric breakdown (D48/50) > 50 kV
Dielectric strength 20 MV/m
Relative permittivity (A) 4.8
Relative permittivity (D24/23) 4.8
Dissipation factor (A) 0.017
Dissipation factor (D24/23) 0.018
Dielectric constant permittivity 4.70 max., 4.35 @ 500 MHz, 4.34
@ 1 GHz
Glass transition temperature Can vary, but is over 120 °C
Young's modulus – LW 3.5×106 psi (24 GPa)
Young's modulus – CW 3.0×106 psi (21 GPa)
Coefficient of thermal expansion -
x-axis
1.4×10−5 K−1
y-axis
1.2×10−5 K−1
z-axis
7.0×10−5 K−1
Poisson's ratio – LW 0.136
Poisson's ratio – CW 0.118
LW sound speed 3602m/s
SW sound speed 3369m/s
LW Acoustic impedance 6.64 MRayl
APPENDIX II

HFSS
HFSS (High Frequency Structural Simulator) software is considered the industry standard for 3D
electromagnetic structure simulation. It is considered as an essential tool for high speed and
high frequency component designs. HFSS offers solver technologies based on either integral
equation method or finite element method. It’s up to you which method to select for the
simulation to be performed.
HFSS solvers are equipped with automated solution methods so all you need to do is to specify
the geometry, the properties of material and output. From here on wards HFSS will take charge
and will generate a mesh for solving the problem.
Features of HFSS Software
High speed, high frequency component modeling.
Solver technologies are based on several methods.
Can select the appropriate method amongst integral equation method or finite element
method.
Equipped with automated solution methods.
One can achieve high-frequency, high-speed component design with state-of-the-art tools from
ANSYS. ANSYS HFSS delivers the most accurate EM simulation results, every time.
Since performance of electronic devices depends on electromagnetic (EM) behavior, you need a fast,
accurate account of how your design will behave in real-world implementations —long before any
prototype is built. ANSYS HFSS™ simulation results give you the confidence you need: The
technology delivers the most accurate answer possible with the least amount of user involvement.
As the reference-standard simulation tool for 3-D full-wave electromagnetic-field simulation, HFSS is
essential for designing high-frequency and/or high-speed components used in modern electronics
devices.
Understanding the EM environment is critical to accurately predicting how a component —or
subsystem, system or end product—performs in the field, or how it influences performance of other
nearby components. HFSS addresses the entire range of EM problems, including losses due to
reflection, attenuation, radiation and coupling.
The power behind HFSS lies in the mathematics of the finite element method (FEM) and the integral,
proven automatic adaptive meshing technique. This provides a mesh that is conformal to the 3-D
structure and appropriate for the electromagnetic problem you are solving. With HFSS, the physics
defines the mesh; the mesh does not define the physics. As a result, you can focus on design issues
rather than spend significant time determining and creating the best mesh.
HFSS benefits from multiple state-of-the-art solver technologies, allowing users to match the
appropriate solver to any simulation need. Each solver is a powerful, automated solution process in
which the user specifies geometry, material properties and the desired range of solution
frequencies. Based on this input, HFSS automatically generates the most appropriate, efficient and
accurate mesh for the simulation, thereby leading to the highest-fidelity solution possible.

HFSS results yield information critical to your engineering designs. Typical results include scattering
parameters (S, Y, Z), visualization of 3-D electromagnetic fields (transient or steady-state),
transmission-path losses, reflection losses due to impedance mismatches, parasitic coupling, and
near- and far-field antenna patterns
Car in an echoic chamber with
Test antenna and antenna fields
HFSS, part of the ANSYS high-frequency electromagnetic design port folio, is integrated with ANSYS
Work bench for coupling EM effects into multi physics analyses, such as temperature and
deformation.

TDR time domain response plot of connector vs. various angles
Engineers can use HFSS with confidence, knowing that they have achieved an accurate solution set
regardless of the type of EM simulation performed.
To solve the most demanding high-frequency simulations, all HFSS solvers are equipped with high
performance computing (HPC) options including domain decomposition and distributed processing.
HPC decreases computation time and leverages existing computer resources to more rapidly solve
very large simulations.
References
1. “Antenna Theory, Third Edition, Analysis and design” By Constantine A. Balanis, 2005, John Wiley
and Sons Inc.
2. “Design and Analysis of Microstrip Patch Antenna Arrays” – Ahmed FatthiAlsager.
3. “Bandwidth enhancement of dual patch microstrip antenna array using dummy EBG patterns on
feedline” by MANIK GUJRAL B.Eng. (Hons.), NUS in 2007.
4. “Design and Simulation of Multiband Microstrip Patch Antenna for Mobile Communications” by
Daniel Mammo.
5. “Design of linearly polarized rectangular microstrip patch antenna using ie3d/pso” - C. Vishnu
vardhanareddy and Rahul rana.

6. Pattern Analysis of “The Rectangular Microstrip Patch Antenna” - Vivekananda Lanka
Subrahmanya.
7. “Development of a Self-Affine Fractal Multiband Antenna for Wireless Applications” - Jagadeesha
S., Vani R. M. & P. V. Hunagund.
8. “A Self-Similar Fractal Antenna with Square EBG Structure” - Jagadeesha.S, Vani R.M, P.V.
Hunagund.
9. “A Self-Affine Fractal Multiband Antenna” - Sachendra N. Sinha, Senior Member, IEEE, and
Manish Jain.
10. “A Self-Similar Fractal Cantor Antenna for MICS Band Wireless Applications” by Gopalakrishnan
Srivatsun, Sundaresan Subha Rani, Gangadaran Saisundara Krishnan.

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