IMPROVED EXPERIMENTAL STUDY OF WAVEGUIDE AND CONICAL HORN
X-BAND ARRAYS FOR NEAR-FIELD CANCER THERAPY APPLICATIONS
Feroz Khan
B.Tech, Jawaharlal Nehru Technological University, India, 2006
Shilpa Reddy Maddula
B.Tech, Jawaharlal Nehru Technological University, India, 2008
PROJECT
Submitted in partial satisfaction of
the requirements for the degrees of
MASTER OF SCIENCE
in
ELECTRICAL AND ELECTRONIC ENGINEERING
and
MASTER OF SCIENCE
in
COMPUTER ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
FALL
2010
IMPROVED EXPERIMENTAL STUDY OF WAVEGUIDE AND CONICAL HORN
X-BAND ARRAYS FOR NEAR-FIELD CANCER THERAPY APPLICATIONS
A Project
by
Feroz Khan
Shilpa Reddy Maddula
Approved by:
__________________________________, Committee Chair
Preetham B. Kumar, Ph.D.
__________________________________, Second Reader
Fethi Belkhouche, Ph.D.
___________________________
Date
ii
Students: Feroz Khan
Shilpa Reddy Maddula
I certify that these students have met the requirements for format contained in the
University format manual, and that this project is suitable for shelving in the Library and
credit is to be awarded for the project.
___________________, Department Chair
Suresh Vadhva, Ph.D.
_________________
Date
Department of Electrical and Electronic Engineering
Department of Computer Engineering
iii
Abstract
of
IMPROVED EXPERIMENTAL STUDY OF WAVEGUIDE AND CONICAL HORN
X-BAND ARRAYS FOR NEAR-FIELD CANCER THERAPY APPLICATIONS
by
Feroz Khan
Shilpa Reddy Maddula
This project focuses on the study of 3-element array of open-ended waveguides
and circular horn antenna operating in the X-band frequency range of 8-12GHz. The 3element array consists of a center focusing element and two surrounding directing
elements. The focusing element is adjusted such that it controls the focus of the array.
Experimental studies have been performed in this project by using different array
configurations and the measured results were compared with earlier simulation results
obtained using the 4NEC2 antenna modeler and optimizer. The goal of our project is to
achieve a closer match between simulated and measured near-field results, as compared
to results obtained in prior projects. The eventual application of this study is for
hyperthermia a treatment of cancer by focused microwave radiation on the affected area.
, Committee Chair
Preetham B. Kumar, Ph.D.
_____________________
Date
iv
ACKNOWLEDGEMENT
It’s a pleasure to thank those who made this project possible. We own our deepest
gratitude to our advisor and graduate coordinator Dr. Preetham Kumar. He has made
available his support in a number of ways throughout this project. This project would not
have been possible without his support. His encouragement and willingness have taught
us new technologies and have improved our knowledge of the subject.
We are very indebted to Dr. Fethi Belkhouche our second reader, for patiently
reviewing this work and for his valuable suggestions in improving the same. We take this
opportunity to thank the management and staff of Computer Engineering and Electrical
Engineering Department for creating an interactive atmosphere for learning.
We would also like to take this opportunity to thank the considerate faculty and
staff of Computer Engineering and Electrical and Electronics Engineering Department
who have been encouraging us throughout our curriculum.
Last but not the least, we would like to extend our thanks to our parents for their
constant encouragement and to all those who have played a small but important role in
this project but could not be individually named here
v
TABLE OF CONTENTS
Page
Acknowledgement ...............................................................................................................v
List of Tables ................................................................................................................... viii
List of Figures .................................................................................................................... ix
Chapter
1. INTRODUCTION .........................................................................................................1
2. BACKGROUND ON HYPERTHERMIA ....................................................................3
2.1 Hyperthermia ..............................................................................................................3
2.2 Hyperthermia in the Treatment of Cancer ..................................................................4
2.3 Methods of Hyperthermia ..........................................................................................4
2.4 Care during Hyperthermia Treatment ........................................................................7
2.5 Advantages and Disadvantages of Hyperthermia ......................................................8
2.6 Side Effects ................................................................................................................8
2.7 Future Scope of Hyperthermia ...................................................................................9
3. BACKGROUND OF ELECTROMAGNETIC RADIATION AND NEAR-FIELD
MEASUREMENT TECHNIQUES .............................................................................10
3.1 Electromagnetic Radiation .......................................................................................10
3.2 Antennas ...................................................................................................................10
3.3 Waveguides ..............................................................................................................10
3.4 Boundary Regions of Electromagnetic Radiations ..................................................10
vi
3.5 Configurations of Near Field ....................................................................................12
4. DESIGN OF CONFORMAL CONICAL HORN ANTENNA X-BAND ARRAY ....16
4.1 X-band Conical Horn Antenna Array ......................................................................16
4.2 Conical Horn Antenna Setup and Measurement ......................................................18
4.3 Rectangular Waveguide Linear Array......................................................................23
4.4 Waveguide Array Setup And Measurements ...........................................................25
5. EXPERIMENT RESULTS OF 3-ELEMENT CONICAL HORN AND 3-ELEMENT
WAVEGUIDE ARRAY ..............................................................................................28
5.1 Experimental Results for the Conical Horn Array ...................................................29
5.2 Experimental Results for Waveguide Array ............................................................33
6. CONCLUSION AND SCOPE FOR FUTURE WORK ..............................................46
References ..........................................................................................................................47
vii
LIST OF TABLES
1. Table 4.1: Element Positions of Linear Array Using Conical Horn Antennas ............18
2. Table 4.2: Element Positions of a Linear Array ..........................................................24
3. Table 5.1: Experimental results of output/input power (A/B) with Z=-11cm, Z=6.1cm and Z=0cm for center element for conical horn antenna array .........................29
4. Table 5.2: Experimental results of S21 with Z=-11cm, Z=-6.1cm, z=0cm for center
element in three element conical horn antenna array...................................................31
5. Table 5.3: Experimental results of output/input power (A/B) for rectangular
Waveguide array with Z=-11cm, Z=-6.1cm, Z=0cm...................................................33
6. Table 5.4: Experimental results of S21 for rectangular waveguide array with Z=-11cm,
Z=-6.1cm, Z=0cm ........................................................................................................35
7. Table 5.5: Experimental results of output/input power (A/B) in dB with Z=0cm in
three element waveguide array with attenuation of 20dB, 15dB and 5dB ..................37
8. Table 5.6: Experimental results of S21 in dB with Z=0cm in three element waveguide
array with attenuation of 20dB, 15dB and 5dB ...........................................................39
9. Table 5.7: Experimental results of output/input power (A/B) in dB with Z=6.1cm in
three element waveguide array with attenuation of 20dB, 15dB and 5dB ..................41
10. Table 5.8: Experimental results of S21 in dB with Z=6.1cm in three element
waveguide array with attenuation of 20dB, 15dB and 5dB .........................................43
viii
LIST OF FIGURES
1. Figure 3.1: Field Regions of Antenna ...........................................................................12
2. Figure 3.2: Planar Near-Field Test Setup ......................................................................13
3. Figure 3.3: Cylindrical Near-Field Test Setup ...............................................................13
4. Figure 3.4: Spherical Near-Field Test Setup..................................................................14
5. Figure 4.1: Schematic Setup of Conical Horn Linear Array Arrangement and
Field Pattern ...................................................................................................................17
6. Figure 4.2: Image of the Horn Antenna Measurement Setup ........................................19
7. Figure 4.3: Schematic Diagram of Feed Network Configuration ..................................21
8. Figure 4.4: Schematic Setup for Three Element Waveguide Arrangement and
Field Pattern ...................................................................................................................24
9. Figure 4.5: Photograph of the Three Element Linear Waveguide Measurement
Setup ..............................................................................................................................25
10. Figure 4.6: Schematic Diagram for Feed Line Network..............................................26
11. Figure 5.1: Two Dimensional Graphs for Experiment of Conical Horn Array for Z=11cm, Z=-6.1cm, Z=0cm As Shown in Table 5.1 .......................................................31
12. Figure 5.2: Two Dimensional Graphs for Experiment of Conical Horn Array for Z=11cm, Z=-6.1cm, Z=0cm for S21 As Shown in Table 5.2 ............................................33
13. Figure 5.3: Two Dimensional Graphs for Experiment of Rectangular Array for Z=11cm, Z=-6.1cm, Z=0cm for S21 As Shown in Table 5.3 ............................................35
14. Figure 5.4: Two Dimensional Graphs for Experiment of Rectangular Array for Z=11cm, Z=-6.1cm, Z=0cm for S21 As Shown in Table 5.3 ...........................................37
15. Figure 5.5: Two Dimensional Graphs for Experimental Results of 3 Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S(A/B) with Z=0cm ..............39
16. Figure 5.6: Two Dimensional Graphs for Experimental Results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S21 with Z=0cm .....................41
ix
17. Figure 5.7: Two Dimensional Graphs for Experimental Results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S(A/B) with Z=6cm ..............43
18. Figure 5.8: Two Dimensional Graphs for Experimental Results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S21 with Z=6cm ...................45
x
1
Chapter 1
INTRODUCTION
Cancer is the development of abnormal cells that divide uncontrollably and destroy the
normal body tissues. Hyperthermia is used in the treatment of cancer. In this treatment
the affected area is exposed to heat at 113º F due to which the cancer causing cells in the
tumor are damaged, as cancer cells are more sensitive to heat than normal cells they can
be destroyed easily. Hyperthermia is more effective when it is used in combination with
other traditional methods like radiation and chemotherapy; it makes the cells sensitive, so
that they can respond to other therapies effectively. Care must be taken so that the good
cells are not destroyed, which requires an intense sharp beam focus on the affected area.
Sharp beam focus is obtained by an accurate antenna setup.
The electromagnetic radiations emanated from the antenna have different
behavior at different distances. The boundary regions of the electromagnetic radiations
are near-field and far-field. These defined boundary regions characterize the behavior of
electromagnetic fields as a function of distance from the source. These fields are the
regions around the source.
In this project, we make use of the near-field region, which is primarily of interest
in medical therapy applications like hyperthermia. The focus of this project is to
accurately characterize a 3-element X-band array, which can be used as an applicator in
medical hyperthermia treatment. Such an array is required to generate a focused
electromagnetic beam on the tumor volume, to increase the temperature to ~ 113 degrees
F. Additionally, by adjusting the position of the focusing element of the array, it is
2
possible to control the beam position within a certain region. Two array types have been
studied: a 3-element array of conical horn antennas, and a 3-element array of waveguides.
An important aspect in the development of such a system is to correlate the
simulation results with measured results. In an earlier student project [13], measured
results did not correlate well with simulated results; measured peaks did not coincide well
with the simulated peaks in the pattern. The focus of this project is to carry out an
measurements on the two array types, with improved an improved measurement setup
and also an improved probe for near-field measurement.
The following is a brief outline of the way the report is organized: Chapter 1:
Introduction, Chapter 2: Background on Hyperthermia, Chapter 3: Background on
Electromagnetic Radiation, Chapter 4: Design of linear conical horn antenna using
conformal X-band, Chapter 5: Experimental results of 3-element horn antenna and 3element waveguide array, Chapter 6: Conclusion and finally References.
3
Chapter 2
BACKGROUND ON HYPERTHERMIA
Cancer is the development of abnormal cells that divide uncontrollably and
destroy the normal body tissues. It can affect a particular part of a body or can spread to
the whole body. There are several existing treatments for treatment of cancer such as
radiation, chemotherapy and surgery. Hyperthermia is one of the methods used for the
treatment of cancer. It involves the application of heat on the affected area, the increased
temperature in this area causes a change in the cells due to which they become
susceptible to other form of cancer treatments. Most of the times it is used in combination
with traditional methods to improve efficiency.
2.1 Hyperthermia
The temperature higher than the normal temperature means Hyperthermia [7].
Hyperthermia also means heat treatment, which in turn means careful usage of heat in
medical treatments. Other names of hyperthermia are thermotherapy and thermal therapy.
In hyperthermia treatment the effected body is exposed to temperature up to ~ 113º F.
This high temperature leads to the damage of the affected cells directly, or make the cells
more susceptible to following radiation or chemotherapy. In various parts of the world
hyperthermia is evolving rapidly as a fourth modality in the treatment of cancer, along
with surgery, radiation and chemotherapy [2, 3].
4
2.2 Hyperthermia in the Treatment of Cancer
When hyperthermia is used by itself it gives impressive results but studies have
showed that the therapeutic effects do not last long enough. However, some of the recent
experimental studies have shown that there was an increase in the percentage cure of
cancer when hyperthermia was used in combination with other traditional methods like
chemotherapy and radiation therapy.
The mechanism behind the therapeutic effect of hyperthermia is not well
established; however it is known that a change in temperature causes changes inside a
cell. The application of heat makes the cancer cells sensitive, so that they can react to
other therapies more effectively and also harm the cancerous cells which may not have
been damaged by the therapies.
Hyperthermia is used in the treatment of many types of cancers some of them
include cancer of head and neck, liver, lung, and appendix [2, 3]. It has to be used
carefully because this his temperature may kill the normal cells of a body [7].
2.3 Methods of Hyperthermia
Some of the different methods of hyperthermia which are currently under study are:
1. Local Hyperthermia
2. Regional Hyperthermia
3. Whole Body Hyperthermia
2.3.1 Local Hyperthermia
Local Hyperthermia is a method in which small tumorous areas are destroyed by treating
them with very high temperature. It is also known as thermal ablation. Different forms of
5
energy can be used to heat the affected area and some among them are radio waves,
ultrasound waves and microwaves [7].
Depending on the location of the tumor the heat may be applied using different methods:
o Intraluminal: This method is used to treat the tumors which are located within or
near body cavities. It uses probes to deliver energy and to heat the area. The probe
used is put into the tumor and its tip releases energy which heats up the tumor .It
is also known as endocavitary method [7, 2].
o External: This method is used to treat the tumors which are located near the body
surface. Machines outside the body are used to raise the temperature of the tumor.
o Interstitial: This method is used to treat tumors which are located deep inside the
body. One of the examples of the tumor which can be treated by interstitial
hyperthermia is brain tumor. In this method probes are used which are inserted
into the tumor of the patient who is under anesthesia. Care has to be taken such
that the probe is inserted properly for this purpose we make used of ultrasound
which is an imaging technique [2].
There is another type of interstitial hyperthermia which makes use of radio waves
to kill cancer cells which is known as Radiofrequency ablation. This is the most
commonly used method and most often it is used to treat tumors that cannot be
removed by surgery. The tumors which are treated using this method are the ones
present in lungs, liver and kidney [7].
6
2.3.2 Regional Hyperthermia
Regional Hyperthermia is a method in which large areas such as limb, organ or a
hollow space within the body are heated. Regional Hyperthermia is usually combined
with other radiation therapies. Some of the methods of regional hyperthermia are
o Deep tissue: Cervical or bladder cancers are treated using this approach. Deep
tissue method makes use of external applicators. The temperature of the organ
that has to be treated is raised by focusing microwave energy with the help of
these applicators which are placed around it.
o Continuous hyperthermia peritoneal perfusion: The space in the body that
contains the stomach, intestines and other digestive organs is called peritoneum.
CHPP is a method which is used along with surgery to treat the cancer in
peritoneum. In this method an anticancer drug which is heated using a warming
device is passed through the peritoneum cavity during surgery. The temperature
used here is in the range of 106º F to 108º F [2, 7].
o Regional perfusion: This method is used in the treatment of sarcomas and
melanomas which are cancers in arms and legs. It is also used in the treatment of
cancers in liver and lung. The patient is given anesthesia before the treatment. The
blood supply to the affected part of the body is not normal to the way blood is
supplied to the rest of the body. The blood of the part is taken into a heading
device, heated and then supplies to the part. The temperature used ranges from
part to part of the body. It is 104º F to 113º F. Other name of regional perfusion is
isolation perfusion [2, 7].
7
2.3.3 Whole Body Hyperthermia
A cancer which affects one part of a body and spreads throughout the body is called
metastatic cancer. Whole Body Hyperthermia is a method which is used for the treatment
of metastatic cancer. This method makes use of hot water blankets, inductive coils and
thermal chambers for the generation of heat. It also makes use of a method where the
patient’s body is immersed in hot water. The temperature used in this method is of the
range of 107º F to 108º F [2, 7].
2.4 Care during Hyperthermia Treatment
Care must be taken during Hyperthermia treatment because excess heat may cause
damage to the normal functioning cells. Needles that have tiny thermometers are used to
measure the temperature of the normal cells surrounding the affected area throughout the
treatment so that their temperature does not exceed limits. These needles are used by the
doctor for patients who have been given anesthesia. Probes and needles that are used in
the treatment must be inserted in the correct place. Doctors make use of imaging
techniques such as ultrasonic and computed tomography to satisfy the same.
Certain parameters that must be considered before applying hyperthermia therapy are:
o Tumor location
o Growth rate of tumor
o History of the tumor
o To know if there is presence of metastases
o General health of the patient
8
Careful treatment under the supervision of highly technical professionals result in
satisfying treatment [2, 7].
2.5 Advantages and Disadvantage of Hyperthermia
One of the major advantages of hyperthermia is that they work more effectively in
combination with other therapies. Other forms of cancer treatments take advantage of
hyperthermia. When the cancer cells are heated at higher temperatures they become
sensitive and they react effectively to radiation and cancer drugs. Treatment using
hyperthermia involves no physical or mental stress it improves the immune system and
during the course of the treatment it does not make the patient ill [8]. The applied
temperature must be given in correct measures and carefully applied. Many new
technologies are evolving for measuring the temperature of the surrounding cells, earlier
probes or needles which have a thermometer on the tip where used now a day’s magnetic
resonance imaging is used which does not require any immersion of needles. Last but not
the least, all body parts do not react the same way to heat, different body part have
different heat requirements.
2.6 Side Effects
Side effects depend on the type of methods used and the part of the body they are
used on. Most of the side effects are caused during the whole body hyperthermia when
compared to other methods. Some of the effects that can be seen are vomiting, diarrhea
and nausea other serious effects are cardiac and vascular disorders which are very rare.
The high temperature used can cause burns, discomfort, pain or blisters. The needles or
probes inserted can cause swelling, blood clots or bleeding. There will not be any side
9
effects observed if the temperature is maintained below 111º F and if there are any, they
are only there for a short period of time. Careful treatment under the supervision of
highly technical professionals result in no side effects [2, 7].
2.7 Future Scope of Hyperthermia
Though Hyperthermia improves the treatment of cancer it is not commonly used
because it is just a experimental technique. Improvements are being made on it by
conducting research and several experiments. Studies are being performed by students on
hyperthermia so that it can be used regularly for the treatment of cancer and also cancers
which affect deeper body parts.
10
Chapter 3
BACKGROUND ON ELECTROMAGNETIC RADIATION AND NEAR-FIELD
MEASUREMENT TECHNIQUES
3.1 Electromagnetic Radiation
A disturbance through a medium or space transferring energy and which is a
function of space and time is called a wave. Motion of electrically charged particles
produce electromagnetic waves and as they are radiated from electrically charged
particles they are also called electromagnetic radiations [4].
3.2 Antennas
They are used to transmit or receive electromagnetic waves. Electromagnetic
radiation is converted to current and vice versa by the antenna. Two or more antennas are
combined together to form an antenna array and these arrays produce a specific
directional radiation pattern.
3.3 Waveguides
They are hollow conductive metal pipes which are used to carry microwaves.
Several applications of microwaves have been developed; some of their important
applications are therapeutic applications in tissue heating. The most promising of all their
applications is hyperthermia [6].
3.4 Boundary Regions of Electromagnetic Radiations
To categorize behavioral characteristics of electromagnetic fields, boundary
regions have to be defined. The radiating antennas behavioral characteristics differs by
distance. There are 3 boundary regions defined which are Far-Field, Transition Zone and
11
Near-Field. These defined boundary regions characterize the behavior of electromagnetic
fields as a function of distance from the source. These fields are the regions around the
source.
An antenna can be measured in the near-field or far-field, the choice of the field is
based on many factors such as cost, size and complexity. For higher frequency antenna
near-field ranges are a better choice than far-field and for lower frequency antennas farfiled antennas are better. One of the advantages of near-field measurement techniques is
that testing can be done indoor which eliminates the many problems caused due to
outdoor distractions such as weather, security, other electromagnetic interference.
The choice of near-field measurement configuration for a particular application
depends on a number of choices. The advantages of spherical near-field measurements
are that they are probe-insensitive, easy to build and any antenna can be measured.
Cylindrical near-field testing has advantages for certain instances as this testing requires
single axis rotation of the antenna. Planar near-field testing is advantageous for antenna
of high directivity [5].
3.4.1 Far-Field: It’s the region which is extending farther than 2 wavelengths away from
the source. These regions are not as expensive as near field regions.
3.4.2 Transition Zone: The region that exists between near field and far field is called
transition zone. It has a combination of properties from both the regions [5].
3.4.3 Near-Field: It’s the region which is located less than 1 wavelength from the source
It is divided into reactive and radiative [5].
12
o Reactive: This is the region which is close to the antenna. As we move away from
the antenna the energy in this region decays rapidly [9].
o Radiative: As we move away from the antenna there is no change in the energy it
remains constant at different distances from the antenna [9].
Figure 3.1.Field Regions of Antenna [5]
3.5 Configurations of Near Field
Different types of near field configurations are:
o Planar: In planar near field setup a probe is used to collect a grid of samples. The
probe is made to move in the X and Y directions along a planar surface for the
collection of these samples. The main advantage of planar near field test setup is
that the antenna which is being tested is stationary [9].
13
Figure 3.2: Planar Near-Field Test Setup [9]
o Cylindrical: In cylindrical near field setup a probe is used to collect a grid of field
samples.
Figure 3.3: Cylindrical Near-Field Test Setup [9]
14
The antenna which is being tested is place in the center on a axial rotator .The probe is
made to move in the Y direction around it. The samples are collected along azimuth and
Y [9].
o Spherical: In spherical near field setup a probe is used to collect a grid of samples.
The samples are collected along phi and theta angle directions. The antenna which
has to be measured is placed on a dual axis rotator. In this setup the probe is kept
stationary and the antenna is rotated [9].
Figure 3.4: Spherical Near-Field Test Setup [9]
The choice of configuration for a particular application depends on the limitations and
advantages of the setup. The best of the three setups is spherical near field, it is easy to
build and the cost to do so is less. For base station type of antennas cylindrical set up is
used. For antennas which have high directivity planar set up is used. Planar set up is best
15
suited for antennas which are very large in size and the data processing in this setup is
simpler when compared to others.
16
Chapter 4
DESIGN OF CONFORMAL CONICAL HORN ANTENNA X-BAND ARRAY
In hyperthermia we make use of heating mechanism for the treatment of parts of the body
which are affected by cancer. They are several heating mechanisms available today for
treating cancer affected tissues, however, the main requirement is an antenna which can
focus the electromagnetic energy on the tumor volume, and thereby cause dielectric
heating. In our project, the focus is on developing effective applicators for hyperthermia
applications by using antenna array configurations. The two antenna arrays we consider
in this work are a three-element X-band array of conical horn antenna, and the other is a
three-element X-band array of rectangular waveguide. The X-band is one of the
frequency band of microwave which ranges between 8 GHz to 12 GHz, in our project we
use a central frequency of 10 GHz [10].
4.1 X-band Conical Horn Antenna Array
Antenna is a transducer which transmits and receives information when it is placed in a
free space. When a group of antennas are interconnected together to obtain a directional
radiation pattern, such a setup is defined as array antenna. If we look into the type of
arrays, the most basic type of array which is easier to implement in terms of geometrical
configuration is linear array where all the array elements center would be along a straight
line. In our experiment all the array elements are equally spaced for all the results.
In this part of the project all the three conical horn antennas array have unequal
current distribution but they are equally spaced to each other. In this set up the center
array element is the focusing element, and the two outer elements are the directing
17
elements. By adjusting the axial position of the central element of the array, we can
control the
position of the near-field beam. In this project, we have considered 3 positions of the
central focusing element: 11cm, 6.1cm and 0cm behind the position of the outer directing
elements. The schematic setup of the three element conical horn array antenna used in the
project is shown in figure 4.1 and table 4.1 displays the relative positions of directing and
focusing elements of linear array of conical horn antenna along the X, Y, Z axis.
Figure 4.1: Schematic Set up of Conical Horn Linear Array Arrangement and
Field Pattern[13]
18
Element number
X-POSITION
(CM)
Y-POSITION
(CM)
Z-POSITION (CM)
DIRECTING (1)
0
-13.5
0
FOCUSSING(2)
0
0
VARIABLE
DIRECTING (3)
0
13.5
0
Table 4.1: Element Positions of Linear Array Using Conical Horn Antennas [13]
4.2 Conical Horn Antenna Setup and Measurement
The entire conical horn antenna setup is divided in to three main parts which are
antenna array, feed line network and the last one is measurement setup. In this setup we
put the entire array structure vertically on a wooden base on a floor and using this array
structure we are going to generate a near field pattern which is measured by receiving
antenna waveguide probe, which is also set up in the same vertical plane. The photograph
of the conical horn antenna and receiving rectangular waveguide probe set up in the
microwave laboratory is as shown in the figure 4.2.
19
Figure 4.2: Image of the Horn Antenna Measurement Setup
o Antenna array
Antenna array can be defined as a group of antennas arranged and interconnected
to obtain a greater gain or to achieve a better beam shaping results. In our horn antenna
setup we divide the antenna array in to two parts: the receiving antenna and the
transmitting antenna array. In the transmitting antenna array all the three elements are
interconnected to each other with the help of T-junctions and waveguide bends. In order
to make sure that we get the correct measurements during the experiment we have used
20
the clamps so that the structure will be stable and remain in one position during the
experiment.
As seen in figure 4.2 we have not used a receiving antenna with a waveguide
flange. The reason for not using the flanged waveguide in this project is because in the
previous project, the measured pattern showed enhanced ripples owing to reflections
from the flanged receiving waveguide. Also, we felt it might be because of these flange
that we were not able to get a beam shaping in the results and that was the additional the
reason for not using the flanged waveguide.
All the elements of the antenna array are fixed in one position and cannot be
moved from the particular position. The receiving side of the antenna array is placed on a
movable wooden block and it is vertically in the same plane as that of transmitting horn
array antenna. In order to have accurate measurements of the near field pattern the entire
structure is covered by absorbing sheets to reduce the losses during the experiment.
o Feed Line Network
Feed line network required for the linear array configurations requires quality
setup but at a minimum cost. Feed line network consists of many things such as Coaxial
cable, Magic Tee, T-junctions and many different types of adaptors, as shown in figure
4.3. The transmitting and receiving antennas are connected to the two ports of the
Network Analyzer to determine the transfer gain between the transmitted and received
signals.
Network analyzer is the most important instrument in this whole project as it
measures the network parameters such as the forward gain S21, and additional A/B. The
21
network analyzer used in our laboratory is the HP8720C which goes from 100 MHz to 20
GHz. In this project, we have used a center frequency of 10 GHz in this experiment and
measured the S and A/B parameters. The figure 4.3 shows the schematic diagram for feed
line network.
Figure 4.3: Schematic Diagram of Feed Network Configuration
22
o Measurement setup
As discussed above, figure 4.2 shows the measurement setup for conical horn
antenna with transmitting array and receiving probe antenna. As seen in figure 4.2, the
receiving antenna array can be moved in both vertical and horizontal directions and it is
attached to T shaped wooden pedestal. A measuring scale has been attached to the
wooden pedestal so that we can deduce at what position the receiving antenna is present
and then accordingly we can take the readings of the experiment at a particular point. In
this experiment we have measured the S21 and A/B parameters at different points by
moving the receiving probe antenna axially along the z-axis at an interval of 5 mm while
keeping the transmitting horn antenna at a fixed position for all 3 configurations of the
central focusing element: a 11cm, 6cm and all in line which is 0cm. The receiving
antenna is connected to port 2 of the network analyzer and the feed line network which is
connected to port 1 of the network analyzer. The operating frequency used in the
experiment is 10GHz which is a X-band frequency and power level used here is 10 dBm.
The final S parameters are calculated is decibel format by network analyzer and the
graphs are plotted for the same.
23
4.3 Rectangular Waveguide Linear Array
In this part of the project, we replace the conical horn antenna array with the
rectangular waveguide array in the transmitting side of the setup and the receiving side
will be same waveguide probe antenna which is housed in the T-shaped pedestal
structure. Here the main concentration is going to be on rectangular waveguides by using
three element linear arrays.
Rectangular waveguides are one of the most used waveguides in microwave
engineering and are used in transporting microwave signals in various applications. Some
of the applications where we use these waveguides are high power systems, precision test
application and many such applications. The rectangular waveguides can propagate in TE
and TM modes but cannot propagate in TEM mode.TM mode is define as a mode where
in the direction of propagation there will be no magnetic component will be present and
in the same way TE mode is a mode where there will be no electric component present in
the direction of propagation [11].
The schematic of the three-element rectangular waveguide array, which
we have practically setup in the microwave laboratory, is shown in the figure 4.4. As seen
in the figure it consists of the transmitting three-element rectangular waveguide array, in
such a way that the center element is adjustable, and we can move the center element for
different axial positions with a view to control the focusing position of the array beam,
whereas the two other side elements are fixed and cannot be moved from their position
24
and are called as directing elements. Table 4.2 shows the position of the directing and
focusing element which is alone the Y, X, Z axis.
Figure 4.4: Schematic Setup for Three Element Waveguide Arrangement and Field
Pattern [13]
Element number
X-POSITION
(CM)
Y-POSITION
(CM)
Z-POSITION (CM)
DIRECTING (1)
0
-13.5
0
FOCUSSING(2)
0
0
VARIABLE
DIRECTING (3)
0
13.5
0
Table 4.2: Element Positions of a Linear Array [13]
25
4.4 Waveguide Array Setup And Measurements
As in the earlier conical array case, the entire setup of rectangular waveguide is divided
in three parts: antenna array, feed line network and the measurement setup. Figure 4.5
shows the set up for the rectangular waveguide array measurement in the microwave
laboratory.
Figure 4.5: Photograph of the Three Element Linear Waveguide Measurement
Setup
26
As we discussed earlier in this part of the project, the feed line network requires many
things such as T-junctions, Coaxial cables, Magic Tee and many different types of
adapters to connect the transmitting and receiving antennas to the network analyzer.
Figure 4.6 shows the schematic diagram for the feed line network.
Figure 4.6: Schematic Diagram for Feed Line Network
27
Measurement Setup
Figure 4.5 shows the measurements set up for the rectangular waveguide antenna array
which has two main parts one is a transmitting antenna and other is a receiving antenna.
As can be seen in the figure the receiving waveguide antenna can be moved in both
vertical and horizontal directions and it is attached to the wooden pedestal so that we can
know at what position the receiving antenna is present and then accordingly we can take
the readings of the experiment at one particular point.
In this experiment we have measured S21 and the A/B parameters at different
points by moving the receiving antenna at interval of 5mm by keeping the transmitting
antenna fixed, for focusing element positions of 11cm, 6cm and 0cm behind the plane of
the directing antennas. The receiving antenna is connected to port 2 of the network
analyzer and the feed line network is connected to the port 1 of the network analyzer. The
center frequency used for this part of the experiment is also 10 GHz which is X-band
frequency. The final S parameter valves is calculated in decibel format by network
analyzer which has larger screen display where we measured the Scattering parameters
A/B and S21 in dual mode.
28
Chapter 5
EXPERIMENT RESULTS OF 3-ELEMENT CONICAL HORN ARRAY AND 3ELEMENT WAVEGUIDE ARRAY
The main aim of our project was to obtain the maximum electromagnetic energy
at one particular point, by using antenna arrays conical horns or open-ended waveguides.
To carry out the accurate near-field characterization of these arrays, we have created an
environment in the laboratory which is disturbance free and to achieve this we have used
absorbers which can keep the actuation losses to minimum extent.
The entire measurement setup is mainly divided into two main parts: one is
transmitting antenna and the other is receiving antenna. Transmitting antenna consists of
many things such as magic tees, adapters, coaxial cable, conical horn antennas and
rectangular waveguides in two different cases. In each of these cases we either use
circular horn or rectangular waveguide as array elements, where the outer directing
elements are at fixed position and the center element can be varied at different length
positions such as 11cm, 6.1cm and 0cm behind the directing elements, to control the
position of the beam. The receiving antenna is fixed at one particular position and cannot
be moved.
In the previous project the results obtained had lot of peaks in the near-field
measurement pattern, and the transition was not a gradual one in all the cases and the
reason we felt for these was because of the rectangular waveguides flanges. So this time
in the receiving antenna side instead of using waveguide with flange, we have cut the
waveguide in two pieces by this we were able to eliminate the waveguide flange.
29
The transmitting and receiving antenna are then connected to each port of the
network analyzer, from which we measured the gain S parameter which is S21 and A/B,
which also gives the ratio of transmitted and received power..In the network analyzer first
we set the center frequency at 10 GHz and also input power at 10 dBm and then we make
the S parameter measurement in network analyzer using dual mode display.
5.1 Experimental Results for the Conical Horn Array
The previous sections have outlined the near-field measurement setup in the laboratory.
The following tables list the measured axial field data, along the z-axis of the array, for
the two array configurations (conical horn and waveguide), and for 3 positions of the
central focusing element, for each array configuration.
1. Experimental results of output/input power (A/B) with Z=-11cm, Z=-6.1cm and Z=-0
cm for center element in three element conical horn array.
The table below lists the near-field A/B transfer ratio measurements for the conical horn
array, while the figure shows the graphical plot of the measurements.
Distance(mm)
Electric Field In dB
Z=-11cm
Electric Field In dB
Z=-6.1cm
Electric Field In dB
Z=0cm
0
5
10
15
20
25
30
-6.2
-7.22
-6.8
-6.71
- 7.67
-7.34
-7.49
-5.2
-4.9
-4.26
-4.5
-4.7
-4.563
-4.999
-8.725
-9.108
-7.388
-5.568
-6.6
-8.17
-7.6
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
- 8.41
-8.2
-8.3
-9.22
-8.87
-8.78
-8.83
-9.24
-9.78
-10.74
-9.69
-9.99
-11.00
-10.57
-10.82
-11.42
-11.08
-11.51
-11.71
-11.2
-11.76
-12.38
-11.49
-13.67
-4.835
-4.9
-5.345
-5.119
-5.243
-5.955
-5.445
-5.582
-5.915
-5.422
-5.763
-5.745
-6.152
-6.309
-6.371
-6.434
-6.999
-6.415
-7.000
-7.415
-7.3
-7.2
-7.461
9.247
-7.145
-5.85
-7.38
-6.64
-5.25
-5.42
-5.52
-4.99
-5.067
-4.99
-5.262
-5.385
-4.99
-5.928
-6.000
-5.2
-6.27
-6.68
-5.5
-6.47
-7.5
-5.7
-6.6
-7.1
Table 5.1: Experimental results of output/input power (A/B) with Z=-11cm, Z=6.1cm, and Z =0cm for center element for conical horn antenna array
31
Associated Graph:
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
-2
-4
-6
A/B(-11)
-8
A/B(-6.1)
A/B(0)
-10
-12
-14
-16
Figure 5.1: Two Dimensional Graphs for Experiment of Conical Horn Array for
Z=-11cm, Z=-6.1cm, Z=0cm As Shown in Table 5.1
2. Experimental results of S 21 with Z=-11cm, Z=-6.1cm and Z=0cm for center element in
three element conical horn array.
The table below lists the near-field S21 transfer ratio measurements for the conical horn
array, while the figure shows the graphical plot of the measurements.
Distance in mm
0
5
10
15
20
S21 in dB
Z=-11cm
-14.79
-15.41
-15.48
-15.21
-15.73
S21 in dB
Z=-6.1cm
-16.8
-16.9
-16.717
-16.592
-17.072
S21 in dB
Z=0cm
-20.4
-18.431
-18.053
-16.5
-16.209
32
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
-15.81
-16.14
-16.67
-16.87
-16.9
-17.48
-17.46
-17.55
-18.01
-18.06
-18.19
-18.76
-18.37
-18.4
-19.17
-19.23
-19.9
-19.58
-19.72
-19.73
-19.99
-19.66
-20.12
-20.41
-20.12
-21.58
-16.934
-16.75
-17.00
-17.101
-17.134
-17.242
-17.431
-17.6
-17.801
-17.735
-17.987
-18.013
-17.805
-18.173
-18.722
-18.383
-18.844
-19.016
-19.114
-19.11
-19.51
-19.425
-19.851
-19.735
-19.400
-21.000
-18.85
-18.3
-16.878
-16.715
-17.999
-16.623
-16.000
-16.011
-15.725
-15.42
-15.38
-15.485
-15.628
-15.295
-15.48
-16.18
-16.64
-15.78
-16.37
-16.38
-16.2
-16.48
-16.98
-16.98
-16.75
-17.65
Table 5.2: Experimental results of S21 with Z=-11cm, Z=-6.1cm, Z=0cm for center
element in three element conical horn antenna array
33
Associated Graph:
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
-5
-10
s21(-11)
s21(-6.1)
s21(0)
-15
-20
-25
Figure 5.2: Two Dimensional Graphs for Experiment of Conical Horn Array for
Z=-11cm, Z=-6.1cm, Z=0cm for S21 As Shown in Table 5.2
5.2 Experimental Results for Waveguide Array
1. Experimental results of output/input power (A/B) with Z=-11cm, Z=-6.1cm and Z=-0
cm for center element in three element waveguide array.
The table below lists the near-field A/B transfer ratio measurements for the rectangular
array, while the figure shows the graphical plot of the measurements.
Distance
mm
Electric field S(A/B)
Z=-11cm
Electric field S(A/B)
Z=-6.1cm
Electric field S(A/B)
Z=0cm
0
5
-14.46
-15.04
-7.63
-7.51
3.61
2.05
34
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
-15.5
-16.05
-16.14
-16.12
-16.21
-16.98
-17.09
-17.43
-17.71
-17.93
-18.53
-19.91
-20.09
-19.86
-19.59
-18.64
-18.66
-19.15
-19.37
-19.47
-20.19
-20.16
-20.6
-21.87
-22.32
-23.01
-25.711
-25.313
-25.77
-8.56
-9.25
-9.32
-10.25
-10.64
-10.91
-11.96
-12.17
-12.89
-12.77
-12.77
-12.96
-13.45
-14.27
-14.81
-15.64
-16.13
-15.92
-16.19
-16.42
-16.22
-16.9
-16.42
-15.97
-15.59
-15.82
-16.23
-16.62
-18.29
2.03
2.48
-0.64
-2.55
-2.29
-3.31
-5.17
-5.66
-6.3
-7.57
-7.95
-8.69
-9.71
-10.11
-10.63
-11.12
-11.26
-11.75
-12.44
-14.04
-13.18
-13.85
-14.04
-14.75
-15.42
-15.78
-16.22
-16.97
-16.19
Table 5.3: Experimental results of output/input power (A/B) for rectangular
waveguide array with Z=-11cm, Z=-6.1cm, Z=0cm
35
Associated Graphs:
10
5
0
1
3
5
7
9
11
13 15
17 19
21 23
25 27
29 31
-5
A/B(-11)
-10
A/B(-6.1)
A/B(0)
-15
-20
-25
-30
Figure 5.3: Two Dimensional Graphs for Experiment of Rectangular Array for
Z=-11cm, Z=-6.1cm, Z=0cm for S (A/B) As Shown in Table 5.3
2. Experiment results of S21 with Z=-11cm, Z=-6.1cm and Z=0cm for center element in
three element waveguide array.
The table below lists the near-field S21 transfer ratio measurements for the rectangular
array, while the figure shows the graphical plot of the measurements.
Distance
mm
S21 in dB
Z= -11cm
S21 in dB
Z=-6.1cm
S21 in dB
Z=0cm
0
5
-24.55
-24.98
-17.21
-17.66
-5.31
-6.11
10
-25.66
-18.114
-6.96
36
15
20
25
30
-25.27
-26.16
-26.119
-26.49
-18.62
-19.38
-19.76
-20.22
-8.49
-9.82
-11.1
-12.25
35
40
45
50
-26.89
-27.09
-27.53
-22.94
-20.85
-21.36
-21.68
-21.78
-13.04
-14.01
-15.24
-16.05
55
-27.93
-22.14
-16.66
60
-28.53
-22.23
-17.44
65
70
75
80
85
90
-29.97
-30.14
-29.78
-29.62
-28.95
-28.61
-22.49
-23.15
-23.79
-24.42
-25.14
-25.69
-18.24
-18.89
-19.71
-20.13
-20.43
-20.82
95
-29.17
-25.74
-21.32
100
105
110
115
120
-29.63
-29.62
-30.44
-30.02
-30.63
-25.85
-26.31
-25.86
-25.71
-25.94
-21.72
-22.24
-22.93
-23.12
-23.78
125
130
135
140
-31.75
-32.22
-33.72
-35.79
-25.53
-25.28
-25.59
-25.73
-24.49
-24.67
-25.22
-25.76
145
150
-36.49
-35.22
-25.00
-27.61
-26.24
-25.76
Table 5.4: Experimental results of S21 for rectangular waveguide array with Z=11cm, Z=-6.1cm, Z=0cm
37
Associated Graph:
0
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31
-5
-10
-15
s21(-11)
-20
s21(-6.1)
s21(0)
-25
-30
-35
-40
Figure 5.4: Two Dimensional Graphs for Experiment of Rectangular Array for
Z=-11cm, Z=-6.1cm, Z=0cm for S21 As Shown in Table 5.3
3. Experimental results of output/input power (A/B) in dB with Z=0 cm in three element
waveguide array with attenuation of 20dB, 15dB and 5dB to central array element.
The table below lists the near-field A/B transfer ratio measurements for the rectangular
array, while the figure shows the graphical plot of the measurements.
Distance
Z in mm
S(A/B) with
attenuation of 15 dB
S(A/B) with
attenuation of 5 dB
0
S(A/B) with
attenuation of 20
dB
-4.39
-10.96
-29.12
5
-6.31
-12.45
-29.10
10
-8.75
-14.66
-32.26
15
-9.9
-16.61
-35.16
20
-10.2
-16.73
-33.19
38
25
-10.89
-17.48
-35.89
30
-12.48
-19.00
-37.16
35
-12.72
-19.78
-39.00
40
-13.48
-19.71
-38.55
45
-13.64
-20.76
-39.20
50
-14.67
-21.96
-40.15
55
-15.14
-22.14
-39.42
60
-17.22
-22.20
-38.70
65
-16.22
-23.86
-39.00
70
-16.34
-23.18
-37.03
75
-16.85
-23.51
-39.45
80
-18.00
-25.00
-44.44
85
-18.34
-25.31
-43.43
90
-18.59
-26.30
-46.54
95
-19.24
-27.70
-56.00
100
-20.00
-28.73
-47.35
105
-20.62
-29.73
-42.44
110
-21.66
-30.36
-41.61
115
-22.09
-30.66
-39.12
120
-22.44
-30.96
-37.73
125
-22.47
-29.76
-35.29
130
-22.34
-28.73
-34.44
135
-22.10
-28.31
-34.48
140
-22.55
-27.66
-34.09
145
-22.12
-27.13
-33.27
150
-21.20
-26.62
-35.73
Table 5.5: Experimental results of output/input power (A/B) in dB with Z=0cm in
three element waveguide array with attenuation of 20dB, 15dB and 5dB
39
Associated Graph:
0
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31
-20
-40
A/B(att of 5dB)
-60
A/B(att of 15dB)
A/B(att of 20dB)
-80
-100
-120
Figure 5.5: Two Dimensional graphs for Experimental Results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S(A/B) with Z=0cm
4. Experimental results of S21 in dB with Z=0cm in three-element waveguide array with
attenuation of 20dB, 15dB and 5 dB with absorber attached to all the elements.
The table below lists the near-field S21 transfer ratio measurements for the rectangular
array, while the figure shows the graphical plot of the measurements.
Distance
Z in mm
S21 with attenuation
of 20 dB
S21 with attenuation
of 15 dB
S21 with attenuation
of 5 dB
0
-16.33
-21.77
-39.34
5
-17.50
-23.17
-39.27
10
-20.11
-25.46
-42.89
15
-20.32
-27.62
-46.44
40
20
-22.22
-27.45
-44.37
25
-24.31
-28.19
-45.14
30
-24.14
-29.99
-47.63
35
-24.39
-30.59
-48.13
40
-24.20
-30.60
-48.77
45
-24.11
-31.63
-49.71
50
-26.27
-32.54
-50.00
55
-26.72
-32.88
-49.89
60
-26.85
-32.96
-48.61
65
-27.32
-33.34
-48.49
70
-27.77
-33.64
-47.59
75
-28.24
-34.18
-49.79
80
-29.48
-35.77
-53.72
85
-30.09
-36.32
-54.90
90
-30.04
-36.82
-56.08
95
-31.09
-38.14
-70.00
100
-31.31
-39.12
-56.61
105
-32.00
-40.31
-53.09
110
-33.31
-41.44
-50.66
115
-32.00
-41.31
-48.72
120
-33.76
-41.97
-47.62
125
-34.00
-39.69
-45.42
130
-33.75
-39.25
-44.31
135
-33.51
-39.72
-45.01
140
-33.96
-38.58
-44.41
145
-33.62
-37.81
-43.05
150
-32.76
-37.42
-45.88
Table 5.6: Experimental results of S21 in dB with Z=0cm in three element waveguide
array with attenuation of 20dB, 15 dB and 5dB
41
Associated Graph:
0
-20
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31
-40
-60
S21 (att of 5dB)
-80
S21 (att of 15dB)
S21 (att of 20dB)
-100
-120
-140
-160
Figure 5.6: Two Dimensional Graphs for Experimental Results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S21 with Z=0cm
5. Experimental results of A/B in dB with Z=6.1cm in three element waveguide array
with attenuation of 20dB, 15dB and 5 dB with absorber.
The table below lists the near-field A/B transfer ratio measurements for the rectangular
array, while the figure shows the graphical plot of the measurements.
Distance
Z in mm
S(A/B) with attenuation
of 20 dB
S(A/B) with
attenuation of 15 dB
S(A/B) with
attenuation of 5 dB
0
-13.05
-18.77
-36.54
5
-14.07
-19.63
-35.62
10
-16.33
-22.03
-39.89
15
-16.62
-21.76
-38.22
20
-16.53
-21.79
-36.23
42
25
-18.72
-23.77
-40.22
30
-18.55
-23.89
-41.17
35
-18.53
-24.09
-40.22
40
-20.27
-25.76
-43.12
45
-20.69
-25.21
-46.63
50
-20.58
-25.69
-42.43
55
-21.23
-26.90
-44.63
60
-21.63
-27.11
-44.44
65
-21.62
-26.52
-42.55
70
-22.77
-28.20
-45.00
75
-23.64
-29.41
-50.00
80
-23.48
-29.70
-47.77
85
-24.37
-30.44
-44.49
90
-24.62
-30.31
-40.66
95
-24.57
-29.66
-39.76
100
-24.75
-29.75
-40.04
105
-25.11
-30.01
-39.78
110
-24.59
-28.59
-37.34
115
-24.44
-28.24
-37.43
120
-24.29
-28.54
-37.12
125
-24.35
-28.01
-37.11
130
-24.31
-27.63
-35.90
135
-24.34
-28.11
-35.99
140
-24.95
-28.48
-37.49
145
-24.77
-28.69
-37.07
150
-24.47
-31.07
-45.70
Table 5.7: Experimental results of output/input power (A/B) in dB with Z=6.1cm in
three element waveguide array with attenuation of 20dB, 15dB and 5dB
43
Associated Graph:
0
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31
-20
-40
A/B(att of 5dB)
-60
A/B(att of 15dB)
A/B(att of 20dB)
-80
-100
-120
Figure 5.7: Two Dimensional graphs for experimental results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S (A/B) with Z=6.1cm
6. Experimental results of S21 in dB with Z=6.1cm in three element waveguide array with
attenuation of 20dB, 15dB and 5dB with absorber.
The table below lists the near-field S21 transfer ratio measurements for the rectangular
array, while the figure shows the graphical plot of the measurements.
Distance
Z in mm
S21 with attenuation
of 20 dB
S21 with attenuation
of 15 dB
S21 with attenuation
of 5 dB
0
-21.44
-28.12
-44.24
5
-22.84
-29.56
-43.54
10
-24.98
-31.36
-47.62
15
-25.05
-31.24
-45.93
20
-25.30
-31.36
-44.67
44
25
-26.72
-33.77
-48.49
30
-26.91
-33.47
-48.80
35
-27.19
-33.39
-47.84
40
-28.78
-35.23
-50.23
45
-29.14
-35.81
-52.11
50
-29.005
-35.36
-50.73
55
-29.52
-36.11
-50.20
60
-29.97
-36.76
-53.81
65
-30.07
-36.40
-51.78
70
-31.19
-37.57
-53.55
75
-32.97
-38.86
-55.88
80
-32.07
-39.41
-55.06
85
-32.95
-40.22
-52.31
90
-32.93
-39.79
-47.82
95
-32.83
-39.12
-47.72
100
-33.27
-39.41
-47.81
105
-33.59
-39.48
-46.38
110
-33.001
-38.55
-45.17
115
-32.72
-38.16
-46.91
120
-32.78
-38.14
-45.04
125
-32.77
-37.65
-44.04
130
-32.72
-37.84
-42.99
135
-32.97
-37.58
-43.78
140
-33.24
-37.83
-44.77
145
-33.15
-38.29
-45.93
150
-34.84
-40.63
-54.72
Table 5.8: Experimental results of S21 in dB with Z=6.1cm in three element
waveguide array with attenuation of 20dB, 15dB and 5dB
45
Associated Graph:
0
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31
-20
-40
-60
S21 (att of 5dB)
S21 (att of 15dB)
-80
S21 (att of 20dB)
-100
-120
-140
Figure 5.8: Two Dimensional Graphs for Experimental Results of Three Element
Waveguide with 20dB, 15dB and 5dB Attenuation for S21 with Z=6.1cm
46
Chapter 6
CONCLUSION AND SCOPE FOR FUTURE WORK
The main scope of this project was to study the beam forming properties of a 3element array of conical horns, and a 3-element array of rectangular waveguides. The
beam focusing is desired in the near-field of the array, for possible microwave
hyperthermia applications, where it is essential to generate a precise beam to focus on the
tumor, and cause heating.
In the microwave laboratory, different array designs have been studied earlier for
near-field beam forming including S-band frequency of 2.45 GHz, and K-band frequency
of 18 GHz. These arrays showed quite significant beam forming, with a capability to
control the beam position by moving the central focusing element along the axial
direction. However, the current work focused on the X-band frequency of 10 GHz, and
results consistently showed that significant beam forming is not achieved in the measured
field. This, in itself is a different result, and it needs to be studied further, why this
frequency is not suitable for beam forming, even by using an antenna array. The negative
result of this project may have potential applications in locating safe electromagnetic
frequencies for commercial use, which do not appreciably cause acculumulation of
electromagnetic power.
47
REFERENCES
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[3] Jawwad Hussain, Khawaja Muhammad Ali, “Hyperthermia planning system for
tumor treatment using 27MHz aperture antenna”. Master of Science Project, Department
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[8] “Valley Cancer Institute”, retrieved from:
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48
[9]”Agilent Technologies”, retrieved from:
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[10] Daniel George Neuman 2, ‘Optimization of Microstrip Patch Antenna Array for
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http://www.madmadscientist.com/html/titlepage.htm
[11] David M. Pozar, ‘Microwave Engineering’, Third Edition, John Wiley & Sons
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[13] Chaitanya Patolia, Nuruddin Amin, “Experimental study of conformal X-band
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