1

CHAPTER 1

INTRODUCTION

Microstrip patch antennas are widely used in wireless communications

due to their inherent advantages of low profile, less weight, low cost, and ease

of integration with microstrip circuits. However, the main disadvantage of

microstrip antennas is the small bandwidth. Improvement of broader bandwidth

becomes an important need for many applications such as for high speed

networks. Many methods have been proposed to improve the bandwidth. One of

the methods is introducing slots. To improve bandwidth in our project we

introduced 2 slots in microstrip patch and formed E-shaped antenna. Recently,

high-speed wireless computer networks have attracted the attention of

researchers, especially in the 5-6 GHz band .It finds applications in WiMax and

Indoor and Outdoor WLAN. WiMax frequency band ranging from 2 to 11 GHz

and the standard is IEEE802.16. Current 5 GHz wireless computer network

systems operate in the 5.15-5.35 GHz band, future systems may make use of the

5.72-5.85 GHz band in addition to the 5.15-5.35 GHz band, for even faster data

rates. Our resonant frequency is 5.8GHz. So we are choosing IEEE802.11a/g

network standard. Such networks have the ability to provide high- speed

connectivity (>50 Mb/s) between notebook computers, PCs, personal organizers

and other wireless digital appliances. Many novel antenna designs have been

proposed to suit the standard for high-speed wireless computer networks. The

Ansoft’s HFSS which is the industry standard simulation tool for 3D full-wave

electromagnetic field simulation based on Finite Element Method (FEM) has

been used for simulation. To improve the gain we made (1*2) array and it gives

better gain and better directivity.

2

CHAPTER 2

LITERATURE REVIEW

[1].Microstrip Antenna Array for WiMAX & WLAN Applications

This paper presents the design of microstrip rectangular patch antenna

with center frequency at 2.4 GHz for WiMAX and WLAN application. The

array of four by one (4x1) patch array with microstrip line feeding technique

was designed and simulated.The antenna array designed on Roger5880 substrate

with overall size of 200 x 100 x 1.59 mm3 and dielectric substrate with 𝜀𝑟 = 2.2.

Quarter-wave transformer is used to match the feeding line to the antennas. The

simulation return loss is equal to -32 dB & -30 dB at the freq. of 1.8 GHz & 2.4

GHz respectively. The dimension of the microstrip antenna also has an impact

on the antenna performance because the current is mainly distributed along the

edge on the radiator. The ground plane of the antenna design perform operation

as an impedance matching circuit, and it tunes the input impedance and hence

changes the operating bandwidth with variation of antenna feed size. The

performance was measured and it shows that the array antenna outperform the

single antenna in terms of directivity, bandwidth and gain.

[2].Coax-Fed E-Shaped Microstrip Patch Antenna with Triple Bands

This paper presents a method of designing the millimeter-wave E-Shaped

microstrip antenna which is very suitable for integration with wireless local area

network (WLAN) applications, widely used in the areas of mobile radio and

wireless communication applications, also found very useful in the field of

global navigation satellite systems(GNSS), global positioning system (GPS).

High Frequency Structure Simulator (HFSS) is a high- frequency simulation

software which is based on a finite element method and its accuracy and

powerful features makes it a common tool for antenna designers. The patch was

designed as rectangular shaped resonating on FR4_epoxy substrate with relative

permittivity dielectric constant of 4.4 and height (H) of 1.6mm. The length (L)

of the patch is 27.99mm and width (W) is 37.2 mm. The area of the ground

3

plane sets 74.4 × 55.98 mm2 . To obtain the desired optimum performance in

terms of VSWR and radiation pattern, two rectangular slots with dimension of

19.1mm x 8mm were cut out from both the upper and lower side of the

rectangular patch thus forming the E-shaped patch shape which in turn yields a

significant improvement in terms of the VSWR that became less than two

(VSWR <2) for all the three frequency bands. The two slots were separated by a

distance of 8mm.The designed antenna can achieve triple band performance to

simultaneously cover the 1.18GHz, 2.42GHz and 4.05GHz frequency with

return loss of -12.50dB, -12.60dB and -15.50dB respectively. Good return loss

and radiation pattern characteristics were all obtained in the frequency band of

interest.

[3].Microstrip Patch Antenna for WiMax/WLAN Applications

This paper contains microstrip patch antenna designed with Inset feed

technique. The antenna is mainly intended to be used for WiMAX (2.2-3.4

GHz) & WLAN (2.40–2.48 GHz) wireless applications. The ground plane

dimensions have given as 100×100 mm and patch dimension 35.4×45.6 mm.

The di-electric material of the substrate (εr) selected for this design is glass

epoxy which has a dielectric constant of 4.4 and loss tangent equal to 0.001. The

proposed antenna resonates at 1.65 GHz frequency and has frequency range

from 1.01 to 2.62 GHz giving a wide band width of 88.57%, and maximum

radiating efficiency of about 99%.

[4].Slotted Rectangular Microstrip Antenna for Bandwidth Enhancement

In this paper the bandwidth enhancement of microstrip antennas is

demonstrated by the loading of a pair of right-angle slots and a modified U-

shaped slot in a rectangular microstrip patch. The rectangular patch has

dimensions of 37.3 mm 24.87 mm and is printed on a grounded FR4 substrate of

thickness 1.6 mm, relative permittivity ) 4.4, and size 60 mm 50 mm. In the

proposed antenna, the longer arm of the right-angle slots is in parallel to the

nonradiating edges and its arm length needs to be about 90% of the patch

4

length; the shorter arm is perpendicular to the nonradiating edges and its arm

length should be greater than 40% of the patch width. t the fundamental

resonant frequency of the unslotted rectangular patch antenna is at about 1.9

GHz, with an operating bandwidth of 1.9%. Since the obtained antenna

bandwidths are as large as 4.3–4.6%, the proposed antennas show a much

greater operating bandwidth, more than 2.2 times that of an unslotted

rectangular patch antenna.

5

CHAPTER 3

ANTENNA PARAMETERS

An antenna is an electrical conductor or system of conductors Transmitter

- Radiates electromagnetic energy into space Receiver - Collects

electromagnetic energy from spaceThe IEEE definition of an antenna as given

by Stutzman and Thiele is, “That part of a transmitting or receiving system that

is designed to radiate or receive electromagnetic waves”. The major parameters

associated with an antenna are defined in the following sections.

3.1.ANTENNA GAIN

Gain is a measure of the ability of the antenna to direct the input power

into radiation in a particular direction and is measured at the peak radiation

intensity. Consider the power density radiated by an isotropic antenna with input

power P0

at a distance R which is given by S = P0/4πR

2. An isotropic antenna

radiates equally in all directions, and it’s radiated power density S is found by

dividing the radiated power by the area of the sphere 4πR2.An isotropic radiator

is considered to be 100% efficient. The gain of an actual antenna increases the

power density in the direction of the peak radiation:

Equation 3.1

Gain is achieved by directing the radiation away from other parts of the

radiation sphere. In general, gain is defined as the gain-biased pattern of the

antenna.

6

Equation 3.2

3.2.ANTENNA EFFICIENCY

The surface integral of the radiation intensity over the radiation sphere

divided by the input power P0

is a measure of the relative power radiated by the

antenna, or the antenna efficiency.

Equation 3.3

Where Pr is the radiated power. Material losses in the antenna or reflected

power due to poor impedance match reduce the radiated power.

3.3.EFFECTIVE AREA

Antennas capture power from passing waves and deliver some of it to the

terminals. Given the power density of the incident wave and the effective area

of the antenna, the power delivered to the terminals is the product.

Equation 3.4

For an aperture antenna such as a horn, parabolic reflector, or flat-plate

array, effective area is physical area multiplied by aperture efficiency. In

general, losses due to material, distribution, and mismatch reduce the ratio of

the effective area to the physical area. Typical estimated aperture efficiency for

a parabolic reflector is 55%. Even antennas with infinitesimal physical areas,

such as dipoles, have effective areas because they remove power from passing

waves.

7

3.4.DIRECTIVITY

Directivity is a measure of the concentration of radiation in the direction

of the maximum.

Equation 3.5

Directivity and gain differ only by the efficiency, but directivity is easily

estimated from patterns. Gain—directivity times efficiency—must be measured.

The average radiation intensity can be found from a surface integral over the

radiation sphere of the radiation intensity divided by 4π, the area of the sphere

in steradians:

Equation 3.6

This is the radiated power divided by the area of a unit sphere. The

radiation intensity U(θ,φ) separates into a sum of co- and cross-polarization

components:

Equation 3.7

Both co- and cross-polarization directivities can be defined:

8

Equation 3.8

Directivity can also be defined for an arbitrary direction D(θ,φ) as

radiation intensity divided by the average radiation intensity, but when the

coordinate angles are not specified, we calculate directivity at Umax

3.5.PATH LOSS

We combine the gain of the transmitting antenna with the effective area of

the receiving antenna to determine delivered power and path loss. The power

density at the receiving antenna is given by equation 3.2 and the received power

is given by equation 3.4. By combining the two, we obtain the path loss as given

below.

Equation3.9

Antenna 1 transmits, and antenna 2 receives. If the materials in the

antennas are linear and isotropic, the transmitting and receiving patterns are

identical . When we consider antenna 2 as the transmitting antenna and antenna

1 as the receiving antenna, the path loss is

Equation 3.10

We make quick evaluations of path loss for various units of distance R

and for frequency f in megahertz using the formula

Equation 3.11

where KU

depends on the length units as shown below

9

3.6.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.

Equation 3.12

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 Rrand 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.

10

3.7.ANTENNA FACTOR

The engineering community uses an antenna connected to a receiver such

as a spectrum analyzer, a network analyzer, or an RF voltmeter to measure field

strength E. Most of the time these devices have a load resistor ZL that matches

the antenna impedance. The incident field strength Ei equals antenna factor AF

times the received voltage Vrec

.

We relate this to the antenna effective height:

Equation 3.13

AF has units meter−1

but is often given as dB(m−1

). Sometimes, antenna

factor is referred to the open-circuit voltage and it would be one-half the value

given by equation 3.13. We assume that the antenna is aligned with the electric

field; in other words, the antenna polarization is the electric field component

measured:

Equation 3.14

This measurement may be corrupted by a poor impedance match to the

receiver and any cable loss between the antenna and receiver that reduces the

voltage and reduces the calculated field strength.

3.8.RETURN LOSS

It is a parameter which indicates the amount of power that is “lost” to the

load and does not return as a reflection. Hence the RL is a parameter to indicate

how well the matching between the transmitter and antenna has taken place.

Simply put it is the S11 of an antenna. A graph of s11 of an antenna vs

11

frequency is called its return loss curve. For optimum working such a graph

must show a dip at the operating frequency and have a minimum dB value at

this frequency. This parameter was found to be of crucial importance to our

project as we sought to adjust the antenna dimensions for a fixed operating

frequency. A simple RL curve is shown in figure 3.1.

Figure 3.1: RL curve of an antenna

3.9.RADIATION PATTERN

The radiation pattern of an antenna is a plot of the far-field radiation

properties of an antenna as a function of the spatial co-ordinates which are

specified by the elevation angle (θ) and the azimuth angle (φ). More specifically

it is a plot of the power radiated from an antenna per unit solid angle which is

nothing but the radiation intensity. It can be plotted as a 3D graph or as a 3D

polar or Cartesian slice of this 3D graph. It is an extremely parameter as it

shows the antenna’s directivity as well as gain at various points in space. It

serves as the signature of an antenna and one look at it is often enough to realize

the antenna that produced it. Because this parameter was so important to our

software simulations we needed to understand it completely.

12

3.10.BEAMWIDTH

Beamwidth of an antenna is easily determined from its 2D radiation

pattern and is also a very important parameter. Beamwidth is the angular

separation of the half-power points of the radiated pattern. The way in which

beamwidth is determined is shown in figure 3.2.

Figure 3.2: Determination of HPBW from radiation pattern

3.11.VSWR

The parameter VSWR is a measure that numerically describes how well

the antenna is impedance matched to the transmission line it is connected to.

VSWR stands for Voltage Standing Wave Ratio and is also referred to Standing

Wave Ratio. VSWR is a function of reflection coefficient which describes the

power reflected from the antenna . If the reflection coefficient is given by ,then

VSWR is defined by

VSWR=1+|| / 1+|| Equation 3.15

13

VSWR is always a real number. Smaller VSWR better the antenna is

matched to transmission line and more power is delivered to antenna. The

minimum VSWR is 1. In this case no power is reflected from the antenna which

is ideal. The voltage would have a constant magnitude along the transmission

line. Practically VSWR under 2 is accepted. VSWR measures the potential to

radiate VSWR alone is not sufficient to determine an antenna is functioning

properly

3.12.BANDWIDTH

The bandwidth of the patch is defined as the frequency range over which

it is matched with that of the feed line within specified limits . In other words,

the frequency range over which the antenna will perform satisfactorily. This

means the channels have larger usable frequency range and thus results in

increased transmission. The bandwidth of an antenna is usually defined by the

acceptable standing wave ratio (SWR) value over the concerned frequency

range.

14

CHAPTER 4

TYPES OF ANTENNAS

Antennas can be classified in several ways. One way is the frequency

band of operation. Others include physical structure and

electrical/electromagnetic design. Most simple, non-directional antennas are

basic dipoles or monopoles. More complex, directional antennas consist of

arrays of elements, such as dipoles, or use one active and several passive

elements, as in the Yagi antenna. New antenna technologies are being

developed that allow an antenna to rapidly change its pattern in response to

changes in direction of arrival of the received signal. These antennas and the

supporting technology are called adaptive or “smart” antennas and may be used

for the higher frequency bands in the future. A few commonly used antennas are

described in the following sections.

4.1.YAGI-UDA ANTENNA

Yagi-uda or simply Yagi antennas are the most high gain antennas and

are known after the names of professor S.Uda and Yagi. This antenna consists

of a driven element, a reflector and one or more directors. The driven element is

a resonant half wave dipole usually of metallic rod at the frequency of

operation. The parasitic elements of continuous metallic rods are arranged

parallel to the driven element and at the same line of sight level. The parasitic

elements receive their excitation from the voltages induced by the current flow

in the driver element. The phase and currents flowing due to induced voltage

depend on the spacing between the elements and the reactance of the element.

Fig 4.1:Yagi-UdaAntenna

15

4.2.FOLDED DIPOLE ANTENNA

A dipole antenna consists of two conductors extending in opposite

directions, with a total length that is often, but not always, a half of a

wavelength long. Dipoles are typically oriented horizontally in which case they

are weakly directional: signals are reasonably well radiated toward or received

from all directions with the exception of the direction along the conductor itself;

this region is called the antenna blind cone or null.

Figure 4.2: Dipole antenna

4.3. HELICAL ANTENNA

Helical antenna is the another type of radiator and perhaps it is the

simplest antenna to provide the circularly polarized waves or nearly so which

are used in extra terrestrial communications in which satellite relays are

involved. Helical antenna is broad band VHF and UHF antenna to provide

circular polarization characteristics. It consists of a helix of thicker copper wire

or tubing wound in the shape of a screw thread and used as an antenna with a

flat metal plate called a ground plate.

4.4. Corner Reflector An antenna comprised of one or more dipole elements in front of a

corner reflector, called the corner-reflector antenna, is illustrated in figure 4.3

16

Figure 4.3: Corner-reflector antennas

This antenna has moderately high gain, but its most important pattern

feature is that the forward (main beam) gain is much higher than the gain in the

opposite direction. This is called the front-to-back ratio.

4.5.Microstrip( Patch ) Antennas In spacecraft or aircraft applications, where size, weight, cost,

performance, ease of installation and aerodynamic profile are constraints, low

profile antennas are required. In order to meet these specifications Microstrip or

patch antennas are used. Microstrip patch antennas are popular for low profile

applications at frequencies above 100 MHz. They usually consists of a very thin

metallic strip or patch on a dielectric –coated ground plane (circuit board).

17

CHAPTER 5

MICROSTRIP PATCH ANTENNA In its basic form, 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 Figure.5.1.

Figure 5.1:Microstrip patch antenna

The patch is normally made of conducting material such as copper or gold

and can take any possible shape. The radiating patch and the feed lines are

usually photo etched on the dielectric substrate.

In order to simplify analysis and performance estimation, generally

square, rectangular, circular, triangular, and elliptical or some other common

shape patches are used for designing a microstrip antenna.

For a rectangular patch, the length L of the patch is usually 0.3333λo<L <

0.5 λo, where λo is the free-space wavelength. The patch is selected to be very

thin such that t<<λo (where t is the patch thickness). The height h of the

dielectric substrate is usually 0.003λo≤h≤0.05 λo. The dielectric constant of the

substrate (εr) is typically in the range 2.2 ≤ εr≤12.

Microstrip patch antennas radiate primarily because of the fringing fields

between the patch edge and the ground plane. For good performance of antenna,

a thick dielectric substrate having a low dielectric constant is necessary since it

18

provides larger bandwidth, better radiation and better efficiency. However, such

a typical configuration leads to a larger antenna size. In order to reduce the size

of the Microstrip patch antenna, substrates with higher dielectric constants must

be used which are less efficient and result in narrow bandwidth. Hence a trade-

off must be realized between the antenna performance antenna and dimensions.

Figure 5.2: Typical patch shapes

5.1. PROPERTIES OF A BASIC MICROSTRIP PATCH A microstrip or patch antenna is a low profile antenna that has a number

of advantages over other antennas it is lightweight, low cost, and easy to

integrate with accompanying electronics. While the antenna can be 3D in

structure (wrapped around an object, for example), the elements are usually flat;

Hence their other name, planar antennas. The figure 5.3 shows a patch antenna

in its basic form: a flat plate on a ground plane. The center conductor of a coax

serves as the feed probe to couple electromagnetic energy in and/or out of the

patch. The electric field distribution of a rectangular patch in its fundamental

mode is also shown.

Figure 5.3: Basic microstrip patch antenna with probe feeding

19

The electric field is zero at the center of the patch, maximum (positive) at

one side, and minimum (negative) on the opposite side. It should be mentioned

that the minimum and maximum continuously change side according to the

instantaneous phase of the applied signal. The electric field does not stop

abruptly at the patch's periphery as in a cavity rather the fields extend the outer

periphery to some degree. These field extensions are known as fringing fields

and cause the patch to radiate. Some popular analytic modeling techniques for

patch antennas are based on this leaky cavity concept. Therefore, the

fundamental mode of a rectangular patch is often denoted using cavity theory as

the TM10 mode.

Since this notation frequently causes confusion, we will briefly explain it.

TM stands for transversal magnetic field distribution. This means that only three

field components are considered instead of six. The field components of interest

are: the electric field in the z direction, and the magnetic field components in x

and y direction using a Cartesian coordinate system, where the x and y axes are

parallel with the ground plane and the z axis is perpendicular.

In general, the modes are designated as TMnmz. The z value is mostly

omitted since the electric field variation is considered negligible in the z axis.

Hence TMnm remains with n and m the field variations in x and y direction.

The field variation in the y direction (impedance width direction) is negligible;

thus m is 0. And the field has one minimum to maximum variation in the x

direction (resonance length direction); thus n is1 in the case of the fundamental.

5.2.DIMENSIONS

The resonant length determines the resonant frequency and is about l/2

for a rectangular patch excited in its fundamental mode. The patch is, in fact,

electrically a bit larger than its physical dimensions due to the fringing fields.

The deviation between electrical and physical size is mainly dependent on the

PC board thickness and dielectric constant.

20

A better approximation for the resonant length is:

Equation 5.1 This formula includes a first order correction for the edge extension due to the

fringing fields, with:

L = resonant length

λd = wavelength in PC board

λo = wavelength in free space

εr = dielectric constant of the PC board material

Other parameters that will influence the resonant frequency:

Ground plane size

Metal (copper) thickness

Patch (impedance) width

5.3.METHODS TO ENHANCE GAIN IN MICROSTRIP PATCH

ANTENNA

Most compact microstrip antenna designs show decreased antenna gain

owing to the antenna size reduction. To overcome this disadvantage and obtain

an enhanced antenna gain, several designs for gain-enhanced compact

microstrip antennas with the loading of a high permittivity dielectric superstrate

or the inclusion of an amplifier-type active circuitry have been demonstrated.

Use of a high-permittivity superstrate loading technique gives an increase in

antenna gain of about 10dBi with a smaller radiating patch. An amplifier-type

active microstrip antenna as a transmitting antenna with enhanced gain and

bandwidth has also been implemented.

5.4.APPLICATIONS OF MICROSTRIP PATCH ANTENNAS

Microstrip patch antennas are increasing in popularity for use in wireless

applications due to their low-profile structure. Therefore they are extremely

21

compatible for embedded antennas in handheld wireless devices such as cellular

phones, pagers etc. The telemetry and communication antennas on missiles need

to be thin and conformal and are often microstrip patch antennas. Another area

where they have been used successfully is in satellite communication.

5.5.ADVANTAGES AND DISADVANTAGES OF PATCH ANTENNAS

Some of their principal advantages of microstrip patch antennas are given

below:

• Light weight and low volume.

• Low profile planar configuration which can be easily made conformal to

host surface

• Low fabrication cost, hence can be manufactured in large quantities.

• Supports both, linear as well as circular polarization.

• Can be easily integrated with microwave integrated circuits (MICs).

• Capable of dual and triple frequency operations.

• Mechanically robust when mounted on rigid surfaces.

Microstrip patch antennas suffer from a number of disadvantages as

compared to conventional antennas. Some of their major disadvantages are

given below:

• Narrow bandwidth

• Low efficiency

• Low Gain

• Extraneous radiation from feeds and junctions

• Poor end fire radiator except tapered slot antennas

• Low power handling capacity.

• Surface wave excitation

Microstrip patch antennas have a very high antenna quality factor (Q). Q

represents the losses associated with the antenna and a large Q leads to narrow

bandwidth and low efficiency. Q can be reduced by increasing the thickness of

the dielectric substrate. But as the thickness increases, an increasing fraction of

the total power delivered by the source goes into a surface wave. This surface

22

wave contribution can be counted as an unwanted power loss since it is

ultimately scattered at the dielectric bends and causes degradation of the antenna

characteristics. However, surface waves can be minimized by use of photonic

bandgap structure. Other problems such as low gain and low power handling

capacity can be overcome by using an array configuration for the elements.

23

CHAPTER 6

FEED TECHNIQUES

Microstrip patch antennas can be fed by a variety of methods. These

methods can be classified into two categories- 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 scheme,

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).

6.1.MICROSTRIP LINE FEED

In this type of feed technique, a conducting strip is connected directly to

the edge of the microstrip patch as shown in Figure 3.4. The conducting strip is

smaller in width as compared to the patch and this kind of feed arrangement has

the advantage that the feed can be etched on the same substrate to provide a

planar structure.

Figure 5.1: Microstrip Line Feed

24

The purpose of the inset cut in the patch is to match the impedance of the

feed line to the patch without the need for any additional matching element.

This is achieved by properly controlling the inset position. Hence this is an easy

feeding scheme, since it provides ease of fabrication and simplicity in modeling

as well as impedance matching. However as the thickness of the dielectric

substrate being used, increases, surface waves and spurious feed radiation also

increases, which hampers the bandwidth of the antenna. The feed radiation also

leads to undesired cross polarized radiation. The performance analysis of

different feeding techniques are given below. Since microstrip feed has better

performance characteristics we have chosen microstrip feeding technique.

Table6.1:Performance characteristics of feeding techniques

25

CHAPTER 7

SUBSTRATE

The dielectric constant plays a major role in the overall performance of

the antenna. It affects both the width, in turn the characteristic impedance and

the length resulting in an altered resonant frequency and reduced transmission

efficiency. we are using the FR4 substrate with the permittivity 4.4.

7.1.FR4 SUBSTRATE

"FR" stands for flame retardant.FR-4 (or FR4) is a grade designation

assigned to glass-reinforced epoxy laminate sheets, tubes, rods and printed

circuit boards (PCB).

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.

26

CHAPTER 8

HFSS SOFTWARE

8.1. INTRODUCTION

HFSS is antenna simulation software. Besides that it can be used in the

design of an integrated circuit, a high speed interconnect or any other type of

electronic component, HFSS often is used during the design stage, and is an

integral part of the design process.

8.2.THE MATHEMATICAL METHOD USED BY HFSS HFSS™ uses a numerical technique called the Finite Element Method

(FEM). This is a procedure where a structure is subdivided into many smaller

subsections called finite elements. The finite elements used by HFSS are

tetrahedral, and the entire collection of tetrahedral is called a mesh. A solution is

found for the fields within the finite elements, and these fields are interrelated so

that Maxwell’s equations are satisfied across inter-element boundaries. Yielding

a field solution for the entire, original, structure. Once the field solution has

been found, the generalized S-matrix solution is determined.

27

Figure 8.1: Mathematical method used by HFSS

Mathematically, HFSS solves for the electric field E using equation 8.1 subject

to excitations and boundary conditions.

Equation 8.1 Where HFSS calculates the magnetic field H using equation:

Equation 8.2 The remaining electromagnetic quantities are derived using the

constitutive relations. In practice, to calculate the fields and S-matrix associated

with a structure with ports, HFSS derives a finite element matrix using the

above field equations. The following shows, in principle, the procedure that

HFSS follows:

1. Divide the structure into a finite element mesh using tetrahedral elements.

2. Define testing functions Wn, for each tetrahedron, resulting in thousands

of basis functions.

3. Multiply field equation 8.1 by a Wn and integrate over the solution

volume.

Equation 8.3 This procedure yields thousands of equations for n=1,2,…,N

28

Manipulating the N equations, using Green’s theorem and the divergence

theorem yields:

Equation 8.3a For n=1,2,…,N ,

Equation 8.4 rewrites (8.3a) as

Equation 8.5 For n=1,2,…,N Equation (6.5) then has the form

Equation 8.6 Or

Equation 8.7 In the matrix equation, A is a known NxN matrix that includes any

applied boundary condition terms, while b contains the port excitations, voltage

and current sources and incident waves. Once you have solved for x, from equation 8.4, you know E. The above

process is performed automatically by HFSS and is fully independent of user

interaction. HFSS uses the above process repeatedly, changing the mesh in a

very deliberate manner, until the correct field solution is found. This repetitive

process is known as the adaptive iterative solution process and is a key to the

highly accurate results that HFSS provides.

8.3. THE ADAPTIVE SOLUTION PROCESS IMPORTANCE TO HFSS

The adaptive solution process is the method by which HFSS

guarantees that a final answer to a given EM problem is the correct answer.

It is a necessary part of the overall solution process and is the key reason

why a user can have extreme confidence in HFSS’s accuracy.

29

Figure 8.2.Adaptive solution process

8.4.THE SIX GENERAL STEPS IN AN HFSS SIMULATION There are six main steps to creating and solving a proper

HFSS simulation. They are:

1.Create model/geometry

2.Assign boundaries

3.Assign excitations

4. Set up the solution

5.Solve 6.Post-process the results

30

Fig 8.3: General steps in HFSS simulation

Every HFSS simulation will involve, to some degree, all six of the

above steps. While it is not necessary to follow these steps in exact order, it is

good modeling practice to follow them in a consistent model-to-model manner. Step one: The initial task in creating an HFSS model consists of the creation of

the physical model that a user wishes to analyze. This model creation can be

done within HFSS using the3D modeler. The 3D modeler is fully parametric

and will allow a user to create a structure that is variable with regard to

geometric dimensions and material properties. A parametric structure, therefore,

is very useful when final dimensions are not known or design is to be “tuned.”

Alternatively, a user can import 3D structures from mechanical drawing

packages, such as SolidWorks®, Pro/E® or AutoCAD®. Geometry, once

imported into HFSS, can be modified within the 3D modeling environment.

This will then create geometry that can be parameterized. Step two: The assignment of “boundaries” generally is done next. Boundaries

are applied to specifically created 2D (sheet) objects or specific surfaces of 3D

objects. Boundaries have a direct impact on the solutions that HFSS provides;

therefore, users are encouraged to closely review the section on Boundaries in

this document. Step Three: After the boundaries have been assigned, the excitations (or

ports)should be applied. As with boundaries, the excitations have a direct

impact on the quality of the results that HFSS will yield for a given model.

31

Because of this, users are again encouraged to closely review the section on

excitations in this document. While the proper creation and use of excitations is

important to obtaining the most accurate HFSS results, there are several

convenient rules of thumb that a user can follow. These rules are described in

the excitations section.

Step Four: Once boundaries and excitations have been created, the next step is

to create a solution setup. During this step, a user will select a solution

frequency, the desired convergence criteria, the maximum number of adaptive

steps to perform, a frequency band over which solutions are desired, and what

particular solution and frequency sweep methodology to use. Step Five: When the initial four steps have been completed by an HFSS user,

the model is now ready to be analyzed. The time required for an analysis is

highly dependent upon the model geometry, the solution frequency, and

available computer resources. A solution can take from a few seconds, to the

time needed to get a coffee, to an overnight run. It is often beneficial to use the

remote solve capability of HFSS to send a particular simulation run to another

computer that is local to the user’s site. This will free up the user’s PC so it can

be used to perform other work. Step six: Once the solution has finished, a user can post-process the results.

Post processing of results can be as simple as examining the S-parameters of the

device modeled or plotting the fields in and around the structure. Users can also

examine the far fields created by an antenna. In essence, any field quantity or

S,Y,Z parameter can be plotted in the post-processor. Additionally, if a

parameterized model has been analyzed, families of curves can be created.

8.5.SOLUTION TYPES

HFSS has three solution types. The Driven Modal solution type is used

for most HFSS simulations, especially those that include passive, high-

frequency structures such as microstrips, waveguides, and transmission lines.

For simulations that deal with Signal Integrity issues, the Driven

Terminal Mode, is used. These simulations generally include models that have

32

multi-conductor transmission lines.

The Eigen mode solver will provide results in terms of Eigenmodes or

resonances of a given structure. This solver will provide the frequency of the

resonances as well as the fields at a particular resonance

8.6. BOUNDARIES IN HFSS

Within the context of HFSS, boundaries exist for two main purposes:

a. To either create an open or a closed electromagnetic model or,

b. To simplify the electromagnetic or geometric complexity of the

electromagnetic model.

While the concept of boundaries can be confusing to an HFSS user, they

can be simply thought of serving two main purposes. The first of these is to

create either an open or a closed model.

A closed model simply represents a structure, or a solution volume,

where no energy can escape except through an applied port. For an Eigen mode

simulation, this could be a cavity resonator. For a driven modal or terminal

solution, this could be a waveguide or some other fully enclosed structure.

An open model represents an electromagnetic model that allows

electromagnetic energy to emanate or radiate away. Common examples would

be an antenna, a PCB, or any structure that is not enclosed within a closed

cavity. While most HFSS simulations deal with models that are open, by

default, HFSS initially assumes that any given model is closed. HFSS assumes

all outer surfaces of the solution space are covered, or coated, by a perfect

electric conductor boundary. In order to create an open model, a user will need

to specify a boundary on the outer surfaces that will overwrite the default

perfect electric conductor boundary.

The second reason why boundaries are used within HFSS is to decrease

the geometric/electromagnetic complexity of a given structure or model. These

boundaries should only be used internally to a model or possibly on a symmetry

plane. They should be applied to specifically created 2D sheet objects or to

specific surfaces of3D objects. While boundaries can be very useful, a user

should exercise caution when using them as they can create unintended results if

33

applied incorrectly.

Every HFSS model a user creates will use boundaries on the outer

surfaces of the solution space. This is a direct result of the fact that a user must

specify whether a given model is open or closed. As a result, any given HFSS

model will always either have Conducting, Radiation, or Perfectly Matched

Layer Boundary on all outer surfaces.

Conducting boundaries are the perfect electric conductor, finite

conductivity, or impedance boundary. Not every HFSS model, however, will

use simplifying boundaries. When using boundaries to create simpler models,

users should take care to not create a model that has unreasonable or

inappropriate boundaries applied.

There are twelve boundaries within HFSS. Boundaries are applied to

specifically create 2Dsheet objects, or surfaces of 3D objects. The twelve

boundaries are:

1. Perfect Electric Conductor (PEC): default HFSS boundary fully

encloses the solution space and creates a closed model.

2. Radiation: used to create an open model.

3. Perfectly Matched layer (PML): used to create an open model and.

preferred for antenna simulations.

4. Finite Conductivity: allows creation of single layer conductor.

5. Layered Impedance: allows creation of multilayer conductors and thin

dielectrics.

6. Impedance: allows creation of ohm per square material layers.

7. Lumped RLC: allows creation of ideal lumped components.

8. Symmetry: used to enforce a symmetry boundary.

9. Master: used in conjunction with Slave Boundary to model infinitely

large repeating array structures.

10. Slave: used in conjunction with Master Boundary to model large

infinitely repeating array structures.

11. Screening Impedance: allows creation of large screens or grids.

12. Perfect H: allows creation of a symmetry plane.

34

8.6.1. Perfect Electric Conductor

The Perfect Electric Conductor or PEC Boundary is the HFSS default

boundary that is applied to all outer faces of the solution space. It represents a

lossless perfect conductor. This default boundary creates a closed model. This

boundary can also be used to create a symmetry plane if it is placed on an outer

face of the solution space.

Figure 8.4: Cavity resonator showing the default Perfect Electric

Boundary on all outer solution space surfaces

8.6.2. Radiation Boundary

The Radiation Boundary is used to create an open model in HFSS. It

should only be appliedto outer faces of the solution space. If simulating an

antenna, the radiation boundary shouldbe placed a quarter wavelength away

from any radiating surface.

35

Figure 8.5: Radiation boundry

8.7. APPLYING BOUNDARIES

Boundaries are applied either to specifically created 2D sheet objects or

to and individual face or faces of one or more 3D objects. Boundaries are

applied in the HFSS modeling window by selecting a face of a 3Dobject or a 2D

sheet object and selecting the boundaries command. The subsequent menu will

allow a user to select which boundary to apply to the selected face(s) or

surface(s). If additional information is needed, a user will have to specify the

appropriate information in the wizard dialogs that appear.

Figure 8.6 Applying boundary

36

8.8. ASSIGNING EXCITATIONS

There are seven types of excitations in HFSS: Wave Ports, Lumped Ports,

Floquet Ports, Incident Fields, Current Sources, Voltage Sources and Magnetic

Bias Source. All excitation types provide field information, but only the Wave

port, Lumped Port, and Floquet port provide S parameters. The use of the

Magnetic Bias Source allows a user model a magnetic bias acting on a ferrite

material.

Figure 8.7: Excitation in HFSS In HFSS, it is with the various excitations that a user can specify the

sources of fields, voltages, charges or currents for a given simulation. The most

commonly used excitation types, or ports, are the wave port and the lumped

port. These ports provide field information as well as S, Y, Z parameters and, in

the case of the wave port, a port wave impedance and gamma, the propagation

constant. The wave impedance and gamma values are related to the

37

transmission line structure that is represented by the wave port.

For models where a magnetic bias is present, such as a circulator, the

magnetic bias source can be used in conjunction with wave or lumped ports to

create a model.

For simulations of large planar and periodic structures such as infinite

antenna arrays, frequency selective surfaces or photonic band gap structures, the

Floquet port can be used.

If an ideal current or voltage source is desired, the current and voltage

sources can be used. However, these sources will only provide field information

and therefore are of limited use in an RF design environment. Only the wave

port and the lumped port types will be discussed in detail in the following

sections.

Both the Wave Port and Lumped Port are available for use in both the

Driven Modal Solution type and the Driven Terminal Solution Type. There is,

however, a small difference in how the ports are set up.

8.8.1. Lumped Port

Lumped Ports are the other commonly used excitation type in HFSS. This

port type is analogous to a current sheet source and can also be used to excite

commonly used transmission lines. Lumped ports are also useful to excite

voltage gaps or other instances where wave ports are not applicable. They

should only be applied internally to the solution space. Shown below are examples of commonly used wave ports with proper size

dimensions.

Fig 8.8: Microstrip model showing a Lumped Port applied between the

signal trace and ground plane

38

Lumped ports are ports that can be used in simulations where energy

needs to be sourced internally to a model. Lumped ports are simpler to create

than wave ports but do not yield as much information as a wave port. Lumped

ports yield S,Y,Z parameters and fields, but they do not yield any gamma or

wave impedance information. The results of a lumped port cannot be de-

embedded but can be renormalized.

Unlike wave ports, lumped ports can support only a single mode. A

lumped port can be defined on any 2D object that has edges which contact two

conducting objects. The boundary that is applied to all edges that do not touch a

conductor is a perfect H, which ensures that the normal electric field is equal to

zero on those edges.

When creating a lumped port, it is necessary that a user draw an

integration line for each port. This integration line should be drawn between the

center points of the edges that contact metal objects. For an example of this, see

the graphic at the end of this section.

The complex impedance Zs, defined when the port was created, serves as

the reference impedance of the S-matrix of the lumped port. The impedance Zs,

has the characteristics of a wave impedance; it is used to determine the strength

of a source, such as the modal voltage V and modal current I, through complex

power normalization.

Figure 8.9: Microstrip lumped port showing integration line (in red). Line

is drawn between along the centre line of the port between the edges that

contact metal objects.

39

It should also be noted that when the reference impedance is a complex

value, the magnitude of the S-matrix is not always less than or equal to 1, even

for a passive device.

Table 8.1: The difference between lumped ports and wave ports

8.9. THE SOLUTION FREQUENCY SETTING

The solution frequency is used by HFSS to determine the maximum

initial tetrahedral size and is the frequency at which HFSS explicitly solves the

given model. The solution frequency is the frequency at which HFSS explicitly

solves a given simulation. It is also at this frequency that the adaptive solution

operates, and it is the fields at this frequency that are used to determine whether

a model has converged or not. The solution frequency should be set to the operating frequency of the

device being simulated. If a frequency sweep result is desired in a simulation,

the solution frequency should be set to a frequency that is 50 percent of the

maximum frequency desired. On a practical note, for most antenna simulations, the solution frequency

should be set to the operating frequency of the antenna. For simulations of

filters, the solution frequency should be set to the center of the band pass

frequency.

The solution frequency is also the frequency that should be used for any

calculations the user performs when creating a model that depend on a

40

frequency. Examples of these types of calculations are air region size for

antenna problems, skin depth calculations, PML wizard input, etc.

Figure 8.10: Solution frequency setting

8.10.THE DELTA- S SETTING The Delta-S parameter is the main convergence criterion used HFSS

when determining whether a model has converged or not.

41

Figure 8.11: Delta- S setting

As mentioned, the adaptive process is a key element to ensuring that

HFSS yields the correct answer. Because of the direct relationship between the

electric fields in a simulation and the calculated S- matrix for that simulation,

the convergence of the simulation is presented to a user via the delta-S value.

The value of delta-S is the change in the magnitude of the S-parameters

between two consecutive passes.

Or, in electric field terms, the change in the electric field distribution

between successive solutions. Once the magnitude and phases of all S-

parameters change by less than the user-specified delta-S value, the analysis

stops and is considered converged. Or conversely, again in electric field terms,

once the electric fields are no longer changing in the given model, the field

solution has converged and is correct.

If the desired delta-S parameter is never reached, HFSS will

continue until the requested number of passes is completed. The maximum delta-S is defined as

Equation 8.8 where:

• i and j cover all matrix entries.

• N represents the pass number.

42

The delta-S number should be set between 0.005 and 0.01 for the

majority of HFSS simulations.

8.11.THE MAXIMUM REFINEMENT PER PASS AND MAXIMUM NUMBER OF PASSES AND SETTINGS

The Maximum number of passes is the maximum number of adaptive

iterations HFSS performs in order to reach convergence. The Maximum

refinement per pass is the percentage of tetrahedral elements that are subdivided

with each adaptive pass.

Figure 8.12: Plot showing number of tetrahedral increase versus adaptive

pass. (Maximum refinement per pass set to 30 %.) Refinement percentage and number of adaptive passes are both used in

the adaptive solution process. The refinement percentage specifies the largest

number of tetrahedral that can be subdivided per adaptive pass. The maximum

number of adaptive passes is the maximum number of times HFSS will refine

the mesh in order to try and converge.

The adaptive solution process uses the delta-S, maximum refinement per

pass, and maximum number of passes to converge to the correct answer. The

delta-S and maximum number of passes determine when HFSS will stop the

adaptive solution process. If convergence is reached before the maximum

number of passes has been performed, the solution process will stop. HFSS will

43

stop if convergence is not reached, but the maximum number of passes has been

reached. In such cases, it is recommended to increase the number of passes so

that HFSS can reach convergence.

8.12.THE DIFFERENT FREQUENCY SWEEPS

HFSS has three distinct sweep types: the discrete sweep, the fast sweep,

and the interpolating sweep. Depending on the needs of a user, a particular

sweep type may be preferred. Generally, the solution times required for a

frequency sweep type increase in the following order: fast, interpolating, and

discrete. But, for solutions that require field information at only a few (less than

five)discrete frequency points, the discrete sweep can be faster than either of the

other two. The fast sweep is useful when many frequency points are desired

over a limited frequency range. The interpolating sweep is most useful when

solving problems from DC to a high frequency.

For both the interpolating and fast sweeps, the number of desired

frequency points is not related to the time it takes to generate the frequency

sweep results. Both of these sweeps, in essence, generate a pole-zero transfer

function, and it is the generation of this function that requires the majority of the

solution time. Once the “transfer” function has been generated, S-parameter data

is rapidly.

Figure 8.13: Applying frequency sweep

44

HFSS has three sweep types available: discrete, fast, and interpolating.

The fast sweep generates a full-field solution within the specified frequency

range. The fast sweep is best suited for simulations that have a number of sharp

resonances. A fast sweep is highly accurate in determining the behavior of a

structure near a resonance. The fast sweep works by using the center frequency

of the sweep to create an Eigen value problem that will be used in an Adaptive

Lanczos-Padé Sweep (ALPS) procedure to determine all the field solutions in

the requested frequency range.

Because the fast sweep uses the results of the adaptive process to

generate the Eigen value problem, it is efficient to set the solution frequency to

be equal to the center sweep frequency when using the fast sweep. A key

benefit of the fast sweep is that it allows a user to post-process and display

fields at any frequency and at any location within the frequency sweep. The

interpolating sweep estimates a solution for the S-matrix over an entire

frequency range. HFSS does this by choosing appropriate frequency points at

which to solve for the field solution. HFSS continues to choose frequency

points until the full sweep solution lies within a given error tolerance. The

interpolating sweep is best suited for very broadband frequency sweeps. The

interpolating sweep uses less RAM than a fast sweep. A key benefit of the

interpolating sweep is that it can easily determine the frequency sweep response

from DC to any desired high frequency.

The interpolating sweep, however, only has the solution frequency field

data available for post-processing. Field data for other frequencies within the

interpolating sweep range are therefore not available. The discrete sweep

generates explicit field solutions at specific frequency points in the desired

frequency sweep. The discrete sweep solution time is directly dependent on the

number of frequency points desired. The more frequency steps a user requests,

the longer HFSS will need to complete the frequency sweep. The explicit field

solution is obtained by substituting the desired frequencies into the matrix

45

equation that was created during the adaptive solution process. Each frequency

solution is therefore explicitly based on the adaptive solution, and not

interpolated via a numerical method like the fast and interpolating sweeps.

Arguably, therefore, the discrete sweep is the most accurate sweep

available. It, however, is also the sweep that requires the most time to generate

frequency sweep results when many frequency steps are desired.

8.13.PLOTTING ANTENNA RESULTS

Far field antenna patterns are easily generated by HFSS by again using

the Reports Editor. The procedure is similar to plotting the standard circuit

parameters. But the model should have included either Radiation or PML

boundaries, and a Far Field Setup must be defined before Far Field quantities

can be plotted.

Figure 8.14: Insertion of Far Field Setup

46

Figure 8.15: Plotting antenna results While the plotting of far fields is straight forward, there are some key items a user

should know regarding how HFSS generates far field data. When HFSS generates far field

data, the field values on the radiation surface(s)are used to compute the fields in the space

surrounding

The modeled structure, outside of the solution volume. This space is broken down

into the near field and far field regions, where the near field is the region close to the solution

volume. In general, the electric field in this external region can be written as Equation 8.9 Where S represents the radiation boundary surfaces. J is the imaginary unit. ω is the angular frequency, 2πf. μ0 is the relative permeability of free space.

47

Htan is the component of the magnetic field that is tangential to surface.

Enormal is the component of the electric field that is normal to the surface.

Etanis the component of the electric field that is tangential to the surface. G is the free space Green’s function, given by

Equation 8.10

where k0 is the free space wave number, r, r’ represent the field and source points, respectively, ε0 is the permittivity of free space,

μr and εr are the relative permeability and permittivity of a dielectric, respectively. The r dependence seen above is a key far fields characteristic of a spherical wave.

The far field is a spherical TEM wave, which can be described by the following

equation:

Equation8.11 where η is the intrinsic impedance of free space. When calculating the far fields, the previously discussed far-field approximations

are used, and the result is valid only for field points in the far-field region.

48

CHAPTER 9

ANTENNA DESIGN

The top view of the proposed antenna structure has been shown in Fig.9.1. A simple

rectangular microstrip patch antenna has been taken. Size of the antenna is calculated from

the basic patch antenna equations (C. A. Balanis, 2007) and appropriate changes have been

done to make an E shape patch antenna. With a distance of /2 between the patch 1*2 array

antenna is designed to improve the gain. Microstrip feeding is chosen for the excitation of the

proposed antenna. Power is divided equally using the lossless T-junction power divider with

three transmission lines connected at a single junction. Each transmission line is at a distance

of /4 from the patch.

Figure 9.1:Top view of the proposed antenna

In the first step, a ground of (58.222*25.47)mm is constructed. FR4 substrate is

created above the ground with a thickness of 1.6mm.E-shaped patch is created above the

substrate with the specifications given in the table 1. Another patch is created with a distance

of /2 from the previously created patch to form a 1*2 array. Microstrip feeding is chosen for

the excitation of the proposed antenna. Power is divided equally using the lossless T-junction

power divider with three transmission lines connected at a single junction. Each transmission

line is at a distance of /4 from the patch.

49

Figure 9.2:Structure of single E-patch antenna

9.1: PARAMETERS OF E-SHAPED PATCH ANTENNA

PARAMETER DIMENSION(mm)

L 11.5

W 15.5

L1 2.2

W1 1.94

W2 2.5

W3 6.62

GROUND 58.822*25.47

HEIGHT OF SUBSTRATE 1.6

Table 9.1: Parameters of E-shaped patch antenna

50

9.2.DESIGN EQUATIONS

PATCH WIDTH:

𝑊=(co / 2𝑓r )√(2 /𝜖r + 1)

𝑐o𝑖𝑠 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑙𝑖𝑔ℎt.

PARAMETERS:

𝜖𝑟𝑒𝑓𝑓 = (𝜖𝑟 + 1)/ 2 + ((𝜖𝑟 − 1)/ 2) (1 + 12 (ℎ/ W ))−1 /2 , 𝑊/ ℎ> 1

∆𝐿 /ℎ = (0.412(𝜖𝑟𝑒𝑓𝑓 + 0.3)( 𝑊/ ℎ + 0.264))/ ((𝜖𝑟𝑒𝑓𝑓− 0.258 )(𝑊 /ℎ + 0.8))

PATCH LENGTH:

𝐿=(𝑐𝑜/ 2𝑓𝑟 √𝜖𝑟𝑒𝑓𝑓 )− 2∆𝐿

DISTANCE BETWEEN PATCH & SUBSTRATE IS

3*substrate thickness

51

SIMULATED ANTENNAS IMAGES IN HFSS

Figure 9.3:Base antenna

Figure 9.4: Proposed antenna array

52

CHAPTER 10

RESULTS

The return loss, gain and VSWR of the single and proposed antenna array are plotted

using HFSS. It is observed that the reflection coefficient (S11) is -20.22dB for the desired

frequency band(5.7 to 5.835GHz) with center frequency of 5.8GHz. For the single antenna

the bandwidth obtained is 237.8MHz(-10 dB Bandwidth).The bandwidth is increased to

310.7MHz for the two element array. The obtained return loss, gain and VSWR graph are

shown in figure10.2,figure10.4,figure10.6 respectively. Gain is increased after implementing

array. For the single antenna, gain of 5dB is obtained whereas for the antenna array the gain

is increased to 6.2 dB. The return loss is -16.36dB for single antenna and -20.22dB for array

antenna. The VSWR is obtained as 1.3 for single antenna and 1.13 for array antenna at the

operating frequency 5.8 GHz. Bandwidth and gain are increased by implementing array.

53

SIMULATED RESULTS

Figure 10.1:Return loss of single antenna

Figure 10.2:Return loss of proposed antenna array

54

Figure 10.3: Gain plot of single antenna

Figure 10.4: Gain plot of proposed antenna array

55

3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00Freq [GHz]

0.00

5.00

10.00

15.00

20.00

25.00

VS

WR

(1)

HFSSDesign1XY Plot 3 ANSOFT

m1

Curve Info

VSWR(1)Setup1 : Sw eep

Name X Y

m1 5.8000 1.3120

Figure 10.5: VSWR plot of single antenna

Figure 10.6:VSWR plot of proposed antenna array

56

COMPARISON OF BASE ANTENNA AND PROPOSED ANTENNA ARRAY

Table 10.1: comparison of base antenna and proposed antenna array

57

CHAPTER 11

FABRICATION AND TESTING

Our proposed antenna is fabricated and tested at KARUNYA UNIVERSITY,

COIMBATORE.The front view and back view of the fabricated antenna is shown in figure

11.1 and figure 11.2 respectively. The antenna is tested and return loss is measured. The

testing equipment used are shown in figure 11.3 and figure 11.4.

58

Figure11.1:Front view

Figure11.2:Back view

59

Figure11.3:Testing setup

Figure 11.4:MIC holder with antenna

60

RESULT COMPARISION

PARAMETER SIMULATED VALUE MEASURED VALUE

S11 plot -20.2dB -22dB

Table 11.1:Result comparision

61

Testing certificate

62

CHAPTER 12

CONCLUSION

The proposed antenna in this paper is a good solution for wireless application

specially for Wireless Local Area Network (WLAN)&Worldwide Interoperability for

Microwave Access(WiMax) with a special property of smaller in size. This antenna is simple

and compact and having Microstrip feed. This is printed antenna geometry so it is very easy

to integrate with the radio frequency circuit. The proposed antenna has bandwidth of

approximately 302.7MHz and resonance frequency at 5.8GHz. Thus we can conclude that

the proposed antenna suitable for wireless applications in WLAN & Wimax bands being

smaller in size.

63

REFERENCES

1. Modani Uma Shankar and Jagrawal Gajanand(May-June 2013),A slotted E-shaped

Stacked Layers Patch Antenna for 5.15-5.85GHz Frequency Band Applications,

International Journal of Electronics and Communication Engineering

&Technology(IJECT).

2. M D Sharma,A. Kattaiya and R.S Meena (2012),E-shaped Patch Microstrip Antenna

for WLAN Applications using Probe Feed and Aperture Feed,IEEE conference on

communication system and network technology.

3. Islam M.T.,M.N.Shakib and N.Misran , “Multi Slotted Microstrip Patch Antenna for

Wireless Communication “Progress In Electromagnetics Research Letters,Vol.10,11-

18,2009.

4. Ansoft’s High Frequency Structural Simulator(HFSS): (online)

http://www.ansoft.com.

5. Ghatak R.;Mishra R.K.;Poddar D.R.;, “Perturbed Sierpinski Carpet Antenna With

CPW Feed for frequency agile/broadband operation”, Progress In Electromagnetics

Research B, Vol.1, 29-42,2008.

6. Warren L.Stutsman, Gary A. Thiele, “Antenna Theory and Design”, second edition,

John Whiley & Sons, New York, 1998.

7. Ansari, J. A. and R. B. Ram, “E-shaped patch symmetrically loaded with tunnel diodes

for frequency agile/ broadband operation”, Progress In Electromagnetics Research B,

Vol.1, 29-42,2008.

8. Jean-Francois Zurcher and Fred E.Gardiol, “Broadband Patch Antenna”, 5th edition,

Artechhouse, London, 1995.

9. Pozar, D. M. and D. H. Schaubert, “The Analysis and Design of microstrip antennas

and arrays”, 4th edition, Wiley Interscience, NewYork 2001.

10. J.Gutrman, A. A. Moreira and C. Peixeiro, “Microstrip Fractal antennas for

multistandard terminals”, IEEE Antennas Wireless Propag.Lett.vol.3,pp.351-2004.

11. B. K. Ang and B. K. Chung, “A Wideband E-shaped Microstrip patch antenna for 5-

64

6GHz wireless communications”, Progress In Electromagnetic Research, Pier 75, 397-

407,2007.

12. Liton Chandra Paul, Nahid Sultan, “Design, simulation and performance analysis of a

line feed rectangular microstrip patch antenna” IJESET, Feb 2013.

13. Ali, Zakir; Singh, Vinod kumar;Singh, Ashutosh Kumar, Ayun Shahanaz, “E-Shaped

microstrip antenna on Rogers substrate for WLAN applications”, proc.IEEE, pp342-

345, oct2011.

14. M.1.1.Ammann, M., “Some techniques to improve small ground plane printed

monopole performance”, in Antennas and Propagation Society International

Symposium.2007 IEEE, vol.9.

15. S. L Latif, L. Shafai and S.K.Sharma, Bandwidth Enhancement and Size Reduction of

Microstrip Slot Antennas, IEEE Transactions on Antennas and Propagation, USA,

Vol.53, No.3, pp.994-1003, March-2005.