Polytechnic University of Marche
Department of Information Engineering
Electronic Engineering
Sistema Elettromagnetico di Ausilioper la Corsa di AtletiIpovedenti
Wearable Antenna SystemSupporting Visually ImpairedRunners
Pranvera Kortoci
Master’s Thesis
Ancona - February 11, 2013
Supervisor: Prof. Graziano Cerri ([email protected])
Polytechnic University of Marche
Co-supervisor: Ing. Paola Russo ([email protected])
Polytechnic University of Marche
Abstract
(English)
This master’s thesis investigates nowadays equipments used by athletes
with disabilities such as being visually impaired or blind. The work
concentrates on the efficiency of existing supporting equipments, and
possible improvement to them. Firstly, common concern for athletes with
specific disabilities is discussed. Afterwards the thesis investigates further
a technique for supporting visually impaired runners along the running
path, that is intended as a normal route that the runner follows during
training and/or a lane of the running track in a marathon. The proposed
technique consists of a transmitting antenna subsystem and a receiving
antenna subsystem. The transmitting antennas are placed either in an ad
hoc machine or a car that runs in front of the athlete. There are two
antennas in two opposite edges of the ad hoc machine or car. These two
antennas create two electromagnetic walls which fix the lane’s borders the
runner is intended to run within. As the runner get close to one of the
borders, the signal from one of the transmitting antennas is received by the
receiving antenna placed on the runner’s chest. Afterwards, the acquisition
and the processing of the signal takes place. The key idea is to transform the
received electric signal into vibration. One or more vibration transducer are
placed on the arms of the athlete. Depending on the position of the runner
with regard to the lane’s borders, the vibration transducer placed on the
runner’s right or left arm vibrates, hence informing the athlete to change
his route accordingly.
Astratto
(Italiano)
Questa tesi di laurea magistrale si concentra sulle attrezzature di ausilio
per la corsa di atleti ipovedenti. In una prima fase si e studiato lo
stato dell’arte delle problematiche e delle difficolta che le persone con
handicap visivi ed in particolare gli atleti riscontrano ogni giorno. Si e
proceduto valutando l’efficienza di attrezzature gia esistenti allo supporto
di persone affette da handicap visivi. La parte consistente di questa tesi
si sofferma sullo studio e sullo sviluppo di un sistema elettromagnetico di
supporto agli atleti ipovedenti. L’atleta si puo avvalere dell’aiuto di questo
sistema durante il periodo di allenamento oppure durante la corsa di gare
organizzate come le maratone. Il sistema proposto consiste in una parte
trasmittente ed una ricevente. Il sottosistema trasmittente comprende due
antenne trasmittenti a slot fissate su una struttura posizionata sul paraurti
posteriore di una vettura oppure una macchina ad hoc. Il sottosistema
ricevente comprende un antenna ricevente ed una unita di acquisizione ed
elaborazione del segnale captato. Le due antenne trasmittenti generano
due muri elettromagnetici che delimitano i bordi di un percorso prestabilito
che l’atleta dovra seguire. Allo spostarsi lateralmente dell’atleta, l’antenna
ricevente posta sul petto dell’atleta capta il segnale di uno dei due muri
elettromagnetici che delimitano la corsia di marcia. Avvicinandosi ad uno di
questi bordi, l’atleta entra nella zona di radiazione di una delle due antenne
trasmittenti. A questo punto l’antenna ricevente capta il segnale, il quale
viene elaborato. Questo segnale viene trasdotto e fara pilotare dei sensori
vibrazionali che sono posti sulle braccia dell’atleta. Al variare della quantita
si spostamento laterale dell’atleta rispetto ai due muri elettromagnetici, i
sensori avvertono l’atleta in un tempo adeguato tramite una vibrazione piu
o meno forte. L’atleta, a questo punto, ha l’informazione necessaria di
modificare la sua rotta e riuscire a stare ento i bordi della zona sicura di
corsa.
Preface
This thesis was prepared at Antenna Laboratory, Department of the
Information Engineering, Polytechnic University of Marche (UNIVPM),
Italy.
The thesis deals with an electromagnetic technique at Radio Frequency (RF)
supporting visually impaired/blind athletes. The thesis mainly focuses on
determining a lane the athletes follow and a warning system helping them
to stay within the borders of the lane and follow the right track.
The thesis consists on a summary report, the design of the wearable
receiving antenna, and measurement in MATLAB® 2011a to demonstrate
the proposed technique.
Ancona, February 2013
Pranvera Kortoci
Acknowledgements
I would like to give my gratitude to my supervisor Professor Graziano Cerri
for his invaluable and genuine suggestions.
I thank my co-supervisor Engineer Paola Russo for advising and guiding me
patiently through all my work for this thesis.
I thank Engineer Alfredo De Leo for helping me during the experimental
phase and for his suggestions.
I thank my colleagues Marco Pieralisi, Valerio Petrini, and Desar Shahu for
sharing ideas and opinions that have been helpful to me while carrying out
this project.
I thank Linh for helping and supporting me while I carried out this project
work.
A special thank goes to my family and Amedeo for the strong support I got
through all these years of study.
Ancona, February 2013
Pranvera Kortoci
Contents
Abstract i
Astratto ii
Preface iii
Acknowledgements iv
1 Introduction 11.1 Problem Statement and Methodology . . . . . . . . . . . . . 11.2 Scope of the Thesis . . . . . . . . . . . . . . . . . . . . . . . 21.3 Structure of the Thesis . . . . . . . . . . . . . . . . . . . . . 2
2 Background 32.1 Mobile Navigation Tools . . . . . . . . . . . . . . . . . . . . 42.2 Visually Impaired Athletes . . . . . . . . . . . . . . . . . . . 5
2.2.1 Paralympic Sports . . . . . . . . . . . . . . . . . . . 62.2.2 Athletics . . . . . . . . . . . . . . . . . . . . . . . . . 72.2.3 Guiding Techniques . . . . . . . . . . . . . . . . . . . 8
2.3 Obstacle Detection Systems . . . . . . . . . . . . . . . . . . 92.4 Electromagnetic System for Athletes . . . . . . . . . . . . . 11
2.4.1 Transmitting Subsystem . . . . . . . . . . . . . . . . 122.4.2 Receiving Subsystem . . . . . . . . . . . . . . . . . . 152.4.3 System’s Operating Mode . . . . . . . . . . . . . . . 16
3 Antenna Design 183.1 Microstrip Antennas . . . . . . . . . . . . . . . . . . . . . . 18
3.1.1 Microstrip Antenna Concept . . . . . . . . . . . . . . 193.1.2 Radiation field . . . . . . . . . . . . . . . . . . . . . 193.1.3 Fundamental Limitations . . . . . . . . . . . . . . . . 20
3.2 Evaluation of the Microstrip Antenna Dimensions . . . . . . 223.3 Impedance Matching Network . . . . . . . . . . . . . . . . . 23
3.3.1 Impedance Matching Network . . . . . . . . . . . . . 243.3.2 Matching Network Dimensions . . . . . . . . . . . . . 25
4 Results and Discussion 304.1 Parameters Statement . . . . . . . . . . . . . . . . . . . . . 30
4.1.1 Simulated Parameters . . . . . . . . . . . . . . . . . 314.1.2 Measured Parameters . . . . . . . . . . . . . . . . . . 34
vi
5 Signal Acquisition and Processing 425.1 Overview of the Received Signal . . . . . . . . . . . . . . . . 425.2 Signal Acquisition and Processing System Components . . . 465.3 Amplification and Demodulation of the Signal . . . . . . . . 48
5.3.1 Amplification and Demodulating Board . . . . . . . . 48
6 Conclusions and Future Work 54
Bibliography 57
A Output Signal Strength Evaluation Scripts 59
C h a p t e r 1
Introduction
This master’s thesis work is aimed to investigate a solution for visually
impaired people. Blind or visually impaired people demonstrate difficulties
in performing the daily tasks and interacting with their surrounding
environment. For some of these people, the symptoms can be cured or
treated, but for the remaining the diagnosis is permanent. Many solutions
have been designed and implemented in order to help blind or visually
impaired people while interacting with other people, handling various
situations, and performing daily activities at home or at work. A safe and
independent manner for blind or visually impaired people to perform their
daily tasks has always been a main interest of many researchers in different
disciplines.
1.1 Problem Statement and Methodology
The main challenge for visually impaired people is the presence of obstacles
and the imminent danger that these obstacles might cause to them. In order
to avoid such problems, various obstacle detection and guidance systems
have been designed and produced. However, many of these solutions have
drawbacks such as heavy weight, large dimensions, and limited scan area [1].
Thus, this master’s thesis concentrates on designing and implementing
a novel technique that overcomes many of the disadvantages in existing
solutions.
1.2 Scope of the Thesis 2
1.2 Scope of the Thesis
The scope of this thesis is to design an obstacle detection and warning
vibration system for the blind or visually impaired athletes. The proposed
system can be used by the athletes in training or competing in a marathon
race.
1.3 Structure of the Thesis
This thesis consists of six chapters. Chapter 2 gives a brief introduction
of existing mobile navigation supporting tools for visually impaired people.
Chapter 3 provides an overview of the obstacle detection system and other
accurate evaluations about it.Chapter 4 discusses the results of the system
that has been built. Chapter 5 describes signal acquisition and processing
that results in warning vibrations. Chapter 6 draws the conclusions and
discusses possible improvement of the proposed system in future.
C h a p t e r 2
Background
Great attention has been paid to blind or visually impaired people, and
many solutions have been realized in order to help them overcoming the
difficulties in their daily lives. The key facts about this illness are given
in [2]. Some of them are briefly described in the following
• Around 285 million people are visually impaired worldwide: 39 million
are blind and 246 million have low vision conditions.
• About 90% of the world’s visually impaired live in developing coun-
tries.
• Globally, uncorrected refractive errors are the main cause of visual
impairment; cataracts remain the leading cause of blindness in middle-
and low-income countries.
• The number of people visually impaired from infectious diseases has
greatly reduced in the last 20 years.
• 80% of all visual impairment can be avoided or cured.
There are four levels of visual function, according to the International
Classification of Diseases:
• Normal vision
• Moderate visual impairment
• Severe visual impairment
• Blindness.
2.1 Mobile Navigation Tools 4
Moderate visual impairment combined with severe visual impairment are
grouped under the term “low vision”: low vision together with blindness
represents all visual impairment.
2.1 Mobile Navigation Tools
The term “visual impairment” is used to describe a wide range of conditions
which affect clarity of vision and visual field. Technology can be invaluable
for people with visual impairments, both as a tool for learning and
communication. Many aid equipments exist nowadays for the blind and
visually impaired people. Most of these equipments are usually used within
the living area, to make people’s life easier and more comfortable. Some of
these equipment are [3] listed in the following
• Canes
• Magnifiers
• Talking watches
• Talking clocks
• Smoke detectors
• Braille products
• Talking cooking gadgets
• Voice recognition software
Cane is the first tool used by visually impaired and blind people for centuries.
The cane is a purely mechanical device dedicated to detect static obstacles
on the ground, uneven surfaces, and steps via simple tactile-force feedback.
This device is lightweight, portable, but its range is limited to its own size,
hence it is not usable for dynamic obstacles detection. There are at least
five main varieties, each serving a slightly different need. These varieties are
in the following
2.2 Visually Impaired Athletes 5
(a) Long cane: designed as a mobility tool used to detect objects in the
path of a user.
(b) Guide cane: a shorter cane with a more limited mobility function used
to scan for the steps.
(c) Identification cane or ID cane: used to alert others as to the bearer’s
visual impairment (it has no use as a mobility tool).
(d) Support cane: designed to offer physical stability to a visually impaired
user.
(e) Kiddie cane: designed for the children.
Another option that provides the best travel aid for the blind is the guide
dog. Based on the symbiosis between the disabled owner and his dog, the
training and the relationship to the animal are the keys to success. The
dog is able to detect and analyze complex situations: cross walks, stairs,
potential danger, known paths and more. Most of the information is pass
through tactile feedback by the handle fixed on the animal. The user is
able to feel the attitude of his dog, analyze the situation and also give him
appropriate orders. On the other hand, guide dogs are still far from being
affordable, around the price of a nice car, and their average working time is
limited to the average of approximate seven years.
2.2 Visually Impaired Athletes
While sport has value in everyone’s life, it is even more important in the life
of a person with disabilities. Sport not only has the rehabilitative influence
on the physical body of people with disabilities, but also has rehabilitation
effect in helping them integrating into society. Furthermore, sport helps
them staying mentally healthy and being independent. Nowadays, people
with disabilities participate both in high performance and in competitive
and recreational sports. The number of people with disabilities involved in
sport and physical recreation is steadily increasing around the world. Sports
for athletes with disabilities are divided into three main disability groups:
2.2 Visually Impaired Athletes 6
(i) sports for the deaf, (ii) sports for people with physical disabilities, and
(iii) sports for people with intellectual disabilities. From the late 1980s,
official sporting events for athletes with disabilities began being held such
as Olympic Games or Commonwealth Games.
2.2.1 Paralympic Sports
The International Olympic Committee (IOC) has published its commitment
to equal access to athletics for all people into its charter, which states:
“The practice of sport is a human right. Every individual must have the
possibility of practicing sport, without discrimination of any kind and in
the Olympic spirit, which requires mutual understanding with a spirit of
friendship, solidarity and fair play. Any form of discrimination with regard
to a country or a person on grounds of race, religion, politics, gender or
otherwise is incompatible with belonging to the Olympic Movement” [4].
Figure 2.1: Football 5-a-Side
The Paralympic Sports for visually impaired people are shown in Table 2.1.
2.2 Visually Impaired Athletes 7
Athletics Cycling
Football 5-a-Side Goalball
Rowing Sailing
Lawn Bowls* Alpine Skiing
Nordic Skiing (Cross-Country Skiing)** Nordic Skiing (Biathlon)**
Swimming Judo
Equestrian
Table 2.1: Paralympic Sports for visually impaired people* Discontinued Summer Sports ** Current Winter Sports
2.2.2 Athletics
Referring to the last Paralympic Games London 2012, speed, strength,
power and stamina have been on display during the Athletics competition,
the largest sport at the Paralympic Games. 1,100 athletes competed for
170 gold medals across track, field and road events [5]. In these olympic
games, visually impaired athletes compete with the guidance of a sighted
companion.
Track running short, middle and long distance events are excellent for
quickness, strength and improving the cardiovascular system. The use
of guides depends entirely on the athlete’s visual classification and the
particular event. Guides facilitate the activity by running alongside the
visually impaired athlete, both runners holding on to a tether. Alternatively,
stationary guides positioned around the track call to the runner giving
directional signals.
The athletics events are:
2.2 Visually Impaired Athletes 8
Figure 2.2: London 2012 Paralympics-Athletics
100 m (M& F) 4x100 m (M& F) 200 m (M& F)
400 m (M& F) 800 m (M& F) 1500 m (M& F)
3000 m (M& F) 5000 m (M& F) 10k m road race (M& F)
Marathons (M& F) Pentathlon (M& F)
Table 2.2: Athletics Events
2.2.3 Guiding Techniques
The most common guiding techniques are: (i) verbal direction and (ii)
running with a tether. The verbal direction is given from the guide runner
to the athlete. The athletes that prefer this technique usually are partially
visually impaired. In this technique, talking is crucial. The guide has to be
prepared to instruct the athlete , and the athlete should be prepared as well
to react on time. In this perfect case, the mutual understanding between
the athlete and the guide play a critical role. Guides are compulsory in
the T11 class and optional in T12 (of the two visual-related categories, T11
indicates a greater level of impairment). Due to their extremely delicate
and important job, at the Paralympic Games London 2012, the guides who
assist blind or visually-impaired athletes to a place on the podium have also
been receiving medals for the first time [6].
2.3 Obstacle Detection Systems 9
Running with the tether technique is usually chosen by visually impaired
and/or blind athletes. Athletes and guides are usually linked together by a
tether, which must be made of non-stretch material, tied around the wrists
or held between the fingers. The tether poses similar challenges to running
a three-legged race, so getting the right pairing is crucial; the guide should
has almost equal height to the athlete so they will be able to match stride
patterns, and to synchronise their arms’ and legs’ movements. The guide will
set up the athlete comfortably and ensure their hands are placed correctly
behind the white start line. A good guide must be able to keep pace and
also have the potential to run faster than the athlete, and it is important
that they are not prone to injury. Using verbal cues, guides will instruct
and motivate their athletes as well as making them aware of any bends.
They can also have a crucial job in raising the levels of cheers from an
audience. Like their athletes, guides too have to abide by rules set by the
International Paralympic Committee: so if the guide suffers a false start, so
does the athlete. Guides are required to run within 50 cm of the athlete at
all times, apart from the last 10 m of the race. Guides must not cross the
finish line before the athlete, otherwise the athlete will be disqualified. Both
guide-runners and the athletes must use the starting blocks in all events up
to 400 m. In races 800 m or longer, two guides may be used and up to four
are permitted in marathons [6].
2.3 Obstacle Detection Systems
Many are the obstacle detection systems for visually impaired people. All
these systems have in common the idea to detect obstacles while moving
around in their environment.
The last decades, taking advantage of the development of radar and
ultrasonic technologies, a new series of devices known under the name of
Electronic Travel Aids (ETAs) was developed. Most of these systems are
similar to the radar system. They rely on the same principle: a laser or
ultrasonic beam is emitted in a certain direction in space, then the beam
is reflected back from the obstacles in that direction. A matching sensor is
used for detecting the reflected beam, measuring the distance to the object,
2.3 Obstacle Detection Systems 10
and indicating the information to the user through audible or tactile signals.
The range covered by these devices is up to approximate 5 m. These devices
need high computational capacity, because they require continuous scanning
of the environment [7].
In other systems, the detection of the nearest obstacle is done by a
stereoscopic sonar system, and the device sends back vibro-tactile feedback
to inform the user about obstacle’s location. This system aims at increasing
the mobility of visually impaired people by offering new sensing abilities [8].
The idea of this system is to extend the senses of the user through a
cyborgian interface, which means that the user should use it after a training
period without any conscious effort, as an extension of their own body. One
of the main contributions is the use of sonar based stereoscopic architecture
of the system in order to give spatial information about the obstacles in the
surrounding.
Many researches have been performed to improve autonomy of visually
impaired people and especially their ability to explore their surrounding
environment. Many wearable systems have been developed based on new
technologies, such as laser, sonar, or stereo camera vision for environment
sensing. All of them use audio or tactile stimuli for user feedback. Some
example are listed in the following
• C-5 Laser Cane which is based on optical triangulations to detect
obstacles up to a range of 3.5 m ahead. It requires environment
scanning and provides information on the nearest obstacle at a certain
time by mean of acoustic feedback. The laser system measures the
distance to the obstacle, and a sound tone proportional to this distance
is played. This system can be considered the precursor of a large series
of devices that try to replace the cane used by blind users [9]. It is
important to state that visually impaired people rely very much on
their sense of hearing, hence it is counterproductive to perturb it.
• Recently, a new obstacle detection system is developed at the
University of Verona. The system use stereoscopic cameras coupled
2.4 Electromagnetic System for Athletes 11
with a laser pointer and audio system. The main interest of the
researchers is the transformation of the 3D visual information into
relevant stereoscopic audio stimuli. The sound generated on ear
phones simulates a distant noise source according to the position of
obstacles. This system is implemented on a wearable device, like
a pair of sunglasses equipped with two micro cameras. The vision
algorithms can compute not only the information about the distance to
the obstacle but also about specification of the environment. However
this system suffers some drawbacks such as huge computation power
and sensitivity to light exposure [10].
• The CyARM system is also based on wearable low cost devices. It uses
ultrasonic transducer to detect the distance to the nearest obstacle.
The user has a fixed wire attached to his belt, which serves for passing
the information through variation of the tension. The higher the
tension, the closer the obstacle. This system though, is not hand
free. The users have to scan the environment.
• Ultra Cane system uses a vibration feedback system. It uses a built-in
sonar system and sends back vibrations through a handle according
to the presence of obstacles. This system overcomes the problem that
the traditional White Cane suffers. It can give information about
obstacles before the direct contact with them. No new functionality
has been added compared to white cane system, with regard to
detecting obstacles at head-height.
All above mentioned systems are supposed to let the user’s hands free
therefore the whole system has to be wearable. This requires the system to
be (1) light-weight, and (2) energy efficient (i.e., low battery consuming).
These are the two main challenges that these techniques have to deal with
nowadays.
2.4 Electromagnetic System for Athletes
The proposed electromagnetic system is aimed to support visually impaired
runners. The required functionalities are not limited to detect obstacles on
2.4 Electromagnetic System for Athletes 12
the surrounding while walking and/or dealing with the daily life tasks but
become more specific. This electromagnetic system is designed to help and
support athletes while training or running a marathon, hence it has a high
requirement about reliability.
The proposed system, as seen in Figure 2.3, is divided into transmitting
and receiving subsystems. The transmitting subsystem consists of two
transmitting antennas, while the receiving one consists of one receiving
antenna. The receiving antenna is wearable so that it can be put on
the runner’s chest. The transmitting and receiving subsystems are further
described in detail in the following subsections.
Figure 2.3: Electromagnetic System Scheme
2.4.1 Transmitting Subsystem
The transmitting subsystem is responsible for generating and radiating of
the signal. The elements of the transmitting part are [11]
• Signal generator at 10 GHz
• Radiating elements: transmitting antennas
The two transmitting antennas will be placed on a car or an ad hoc machine
which runs in front of the runner. These antennas should create two
electromagnetic walls, which define the track that the runner should follow
2.4 Electromagnetic System for Athletes 13
Figure 2.4: Transmitting Antenna [11]
Figure 2.5: Virtual Lane and the Runner
or stay within as in Figure 2.5. In order to distinguish between the left or
the right electromagnetic wall, an Amplitude Modulation (AM) has been
implemented. Two modulations at different frequencies are used in order
to distinguish between the radiations by two transmitting antennas. The
radiation pattern of the transmitting antenna is very important. In order to
have electromagnetic walls, the radiation pattern should be narrow on the
horizontal plane and wide on the vertical plane. An aperture width (3 dB)
for the main lobe between 4° − 10° is desirable. In order to obtain such a
radiation pattern, a slot antenna has been chosen.
2.4 Electromagnetic System for Athletes 14
The radiation pattern of the transmitting antenna is shown in Figure 2.6
The measured radiation pattern of the antenna has an Aperture Width (3
Figure 2.6: Radiation Pattern: H Plane [11]
dB) of 4.8°, instead of 3.6°obtained by the simulation. The narrow radiation
pattern in the horizontal plane allows to have an electromagnetic wall.
The radiation pattern of the transmitting antenna in the E plane is shown
in Figure 2.7. This radiation pattern has an Aperture Width (3 dB) of 76°,
Figure 2.7: Radiation Pattern: E Plane [11]
while the simulated Aperture Width (3 dB) is 61°.
2.4 Electromagnetic System for Athletes 15
2.4.2 Receiving Subsystem
The receiving part is responsible for the signal acquisition and processing.
The receiving subsystem consists of following elements
• Receiving antenna
• Amplifier and AM demodulator
• BandPass filters at two different frequencies (distinguish between the
signals sent by the two transmitters)
• Micro Controller Unit (MCU)
• Vibration transducers
The receiving antenna is a microstrip array antenna of four elements. The
radiation pattern of the microstrip array antenna should be wide on the
vertical plane and narrower on the horizontal plane. This choice is dictated
by a preliminary evaluation of the signal received by the wearable antenna.
It is obvious that the signal amplitude depends on the combination of the
radiation patterns of either the antennas.
We would like to have a signal amplitude that gets stronger while the
runner is getting closed to the border of the lane. A threshold is set in
order to activate the warning unit (vibration transducers). Once the signal
amplitude is higher than the threshold, the transducers vibrate and alert the
runner. We want the transducers start vibrating at a certain distance from
the border. This way, the runner will have appropriate space to modify his
route. We do not want the system arise false alarms to the runner, which
means that the signal amplitude should fall significantly once he is out of
the warning range. A reasonable range might be ≈ 20÷ 30cm.
For this purpose, a first evaluation of the radiation pattern the receiving
antenna should have leads to an Aperture Width (3 dB) in the H-plane of
∼ 25°. In the E-plane instead, the Aperture Width (3 dB) is wider, a ∼ 50°sounds reasonable.
2.4 Electromagnetic System for Athletes 16
2.4.3 System’s Operating Mode
The transmitting antennas’ radiation patterns are very narrow in the
horizontal plane, which produce two electromagnetic walls that fix the
borders of the lane followed by the runner. Whenever the runner gets
close to one of the electromagnetic walls, either on the right or the left,
the receiving antenna placed on his chest will receive the signal from the
transmitting antennas.
The combination of the two radiation patterns leads to different levels of the
received signal. As the position of the runner with regard to the transmitting
antennas changes, the level of the received signal changes accordingly. The
vibration transducers placed on the arms of the runner are driven by this
signal. If the receiving signal is over a fixed threshold, the sensors will be
activated. The fixed threshold is set properly in order not to raise false
alarms. Whenever the runner gets close enough to the border of the lane,
the transducers will start vibrating to notify the runner. Based on the
transducers’ vibration, the runner can adjust the route accordingly. If the
received signal does not pass the threshold, the runner will not be warned
by the vibration transducers. If the transducers placed on the right arm
vibrate, the runner aware that he is getting too close to the right border of
the lane and he has to adjust the route. Similarly, if the sensors placed on
the left arm vibrate, the runner is getting too close to the left border of the
lane.
In order to distinguish between the signal sent from the transmitting antenna
placed on the right and from the one on the left, two modulating signals for
the transmitting carrier are used. The modulating signals are different in
their frequencies. The frequencies chosen for the carrier signals are 1 kHz
and 11.3 kHz. These frequencies are chosen in order to reduce the complexity
of the needed hardware. The lower the modulating signal frequency, the
simpler the necessary electronics components need to be used. This allows
to use diodes for the demodulation, which have good performances at low
frequency. The second frequency has been chosen to be at least one order
of magnitude higher than the first one. These choices of signal’s frequencies
have following advantages
2.4 Electromagnetic System for Athletes 17
(a) The two BandPass filters will easily distinguish between the two signals
at 1 kHz and 11.3 kHz
(b) There is no risk that the second modulating signal might be interpreted
as a higher harmonic of the first modulating signal
As mentioned above, even though the second modulating signal is highly
unlikely seen as a higher harmonic of the first modulating signal, there is
still some power carried by higher harmonics of the signal at 1kHz. In order
to avoid all kind of mistaking, the frequency of the second modulating signal
is chosen so that it is not a multiple of the first one.
The demodulation scheme used is an On-Off Amplitude Modulation. The
demodulation scheme of the transducers might differ from the one used for
the received signal. In this case though, there is no difference. The choice
has been dictated mostly by the human response to the vibration stimuli.
The idea is to have the sensor that vibrates in an intermittence way when
the runner is getting close to the lane border, and continuously when the
runner risks to go out of the border dictated by the two electromagnetic
walls. This is the most suitable way to warn the runner, other than using
a Pulse Width Modulation which changes the intensity the sensor vibrates
according to the temporal length width of the impulse.
All engineering choices made for this system are based on basic requirements
the system such as reliability, robustness, and short response time.
C h a p t e r 3
Antenna Design
3.1 Microstrip Antennas
Microstrip is the name given to a type of open waveguiding structure.
The antenna assembly is physically very simple and flat, which present the
main reason for the great interest has been paid on this type of antenna.
Sometimes microstrip antennas are also called printed antennas, because
of the manufacturing process. Last decades microstrip antennas have been
used intensively in many applications such as:
• Satellite communication
• Doppler and other radars
• Radio altimeter
• Command and control
• Missile telemetry
• Weapon fuzing
• Manpack equipment
• Remote sensing
• Biomedical radiator
• Feed elements in complex antennas
This fact is due to the features these antennas have. Features like low
cost, reduced weight and size, ease of installation, aerodynamic profile are
very appealing to applications that require low-profile antennas [12]. On
3.1 Microstrip Antennas 19
the other hand, this type of antenna also has disadvantages such as low
efficiency, low power, low gain (20dB), poor endfire radiation performance,
radiations limited to half a plane, high Q, narrow frequency bandwidth, and
spurious feed radiation.
3.1.1 Microstrip Antenna Concept
The upper surface of the dielectric substrate supports the printed conducting
strip, while the entire lower surface of the substrate is backed by the
conducting ground plate. A wide range of dielectric substrate thicknesses
and permittivities are allowed. Ideally, the dielectric constant εr of the
substrate should be low (ε ≈ 2.5) In some special case, the strip and the
ground are separated by an air space. The ideal arrangement would allow
the conductors together with the feed to be printed onto a single substrate
directly backed with the ground plane. Such assembly shows a further saving
in weight, cost, and results in a thin structure to be mounted conformally
onto many layouts of surfaces.
Figure 3.1: Microstrip antenna: E-field under the patch
3.1.2 Radiation field
The radiation from the microstrip antennas occurs from the fringing fields
between the edge of the microstrip antenna conductor and the ground
plane. The radiation can be better understood by considering the case of a
3.1 Microstrip Antennas 20
rectangular microstrip patch spaced a small fraction of a wavelength above
a ground plane. Due to this fact, no variation of the electric field within the
width is assumed. The electric field varies along the patch length which is
about half a wavelength (λ/2).
Radiation at the open-circuited edges of the patch may be resolved into
Figure 3.2: Patch geometry
normal and tangential components with respect to the ground plane. The
normal components are out of phase because the patch line is λ/2 long.
The tangential components are in phase, therefore the fields combine to
give maximum radiated field normal to the surface (broadside direction).
3.1.3 Fundamental Limitations
Experience with this kind of antenna shows that the bandwidth decreases
proportionally with the distance of separation between the radiating
elements and the ground plane, which means that thinner antennas have
lower bandwidth [13]. The bandwidth definition in this case is the frequency
range within the input match, that is acceptable. It is shown that the
radiation power of a microstrip antenna with constant applied voltage
is essentially independent of the substrate height h, the energy stored is
inversely proportional to h, which leads to Q-factor inversely proportional
to h as well
3.1 Microstrip Antennas 21
Qr =2πfrEs
(1
h
)Pr
(3.1)
where Es(1h) is the stored energy, Pr is the power radiated, and fr is the
frequency.
In case the conduction and dielectric losses are taken into account, the
situation changes because there is power absorbed by these two mechanisms:
Qt =2πfrEs
(1
h
)Pr + Pd + Pc
(3.2)
It is seen from the formula that this leads to an increase in bandwidth.
However, the antenna efficiency η also depends upon the ratio of radiated
power to total input power:
η =Pr
Pr + Pd + Pc
100 (3.3)
Any increase in bandwidth due to loss is thus matched by a proportional
reduction in efficiency. Therefore, the fractional bandwidth of the antenna
is inversely proportional to Qt [12]:
∆f
f0=
1
Qt
(3.4)
The Q-factor varies in the range 20-200 for microstrip antennas.
An additional problem is that the feeder lines introduce additional loss and a
small amount of power can be coupled from one feeder to another by surface
wave action in the dielectric substrate. Therefore the feeders can radiate and
further contribute to the radiation pattern degradation. In this scenario, the
scattering of the surface waves at the edge of the substrate board has to be
controlled, or it might lead to a worse situation of sidelobes.
3.2 Evaluation of the Microstrip Antenna Dimensions 22
3.2 Evaluation of the Microstrip Antenna
Dimensions
A microstrip antenna element is inhere used as part of an array of four
elements. The design procedure follows some elementary step by step rules.
The first layout of the microstrip antenna array is produced by applying
well-known formulas. These formulas will give the dimension of the single
patch element, based on the resonance frequency and the dielectric substrate
material. The substrate material has been chosen for this antenna is ROGER
RT5870 (lossy) of thickness h = 1.570mm and εr = 2.33. The antenna
operating frequency is fr = 10.47 GHz [11], which coincide with the working
frequency of the transmitting antennas. Based on these data, the width W
and the length L of the single element of the array can be computed. The
width W of the single element patch is:
W =c
2fr
√ε+ 1
2(3.5)
where c is the velocity of the light c = 2.997 ∗ 108m/s. In order to compute
the length L of the single element, εe and ∆L should be known. The effective
dielectric constant εe is determined by the formula:
εe =εr + 1
2+εr − 1
2
√1 +
12h
W(3.6)
while the normalized line extension ∆L is determined as follows:
∆L
h= 0.412
(εe + 0.3)(W
h+ 0.264)
(εe − 0.258)(W
h+ 0.8)
(3.7)
Once the above parameters are obtained, the element length L is:
3.3 Impedance Matching Network 23
L =c
2fr√εe− 2∆L (3.8)
Electrically, the single patch of the microstrip antenna looks greater than
its physical dimensions [12, chap. 14]. This is due to the fringing effects.
Figure 3.3: Physical and effective length of the microstrip patch
Therefore, the effective length Leff of the single element can also be written
as:
Leff = L+ 2∆L (3.9)
The resonance frequency is a function of the effective length, therefore the
formula for determining fr of the dominant mode TM010 is:
(fr)010 =1
2Leff√εreff√µ0ε0
(3.10)
The fringing effect depends on the height of the substrate. The higher the
height of the substrate is, the lower the resonance frequency is.
3.3 Impedance Matching Network
Microstrip antennas are commonly used as arrays in order to obtain
the desired performance for a precise application. The most important
parameters that the designers focus on are the radiation pattern and the
directivity. The matching technique is important to provide acceptable
frequency characteristics. Efficient networks must be designed with an
3.3 Impedance Matching Network 24
attempt to couple-match the characteristics of the transmission line-antenna
element over the desired frequency range.
3.3.1 Impedance Matching Network
In order to feed the single elements of the array, a corporate-feed network is
considered. To accomplish this task, quarter-wavelength impedance trans-
formers are used. The corporate-feed arrays are general and versatile [12].
This method allows the designer to have more control of the feed of all single
elements of the arrays.
An example of a corporate-feed network is shown in Figure 3.4
Figure 3.4: Corporate-Feed Network
The multiple-section quarter-wavelength impedance transformers technique
is suitable and the most used with microstrip transmission lines. In
microstrips, the characteristic impedance can be changed by varying the
width of the microstrip line.
This technique implies that the antenna impedance is real. If it is not,
the transformer is placed at a distance s0 from the antenna. This distance
is chosen so that the input impedance toward the load at s0 is real and
designated as Rin. To provide the match, the well-known formula is used:
Z1 =√RinZ0 (3.11)
where Z0 is the characteristic impedance (real) of the input transmission
line [12].
3.3 Impedance Matching Network 25
Figure 3.5: λ0/4 transformer
In order to provide impedance matching, the same analysis has been followed
by using the multiple section.
3.3.2 Matching Network Dimensions
The matching network has been designed in order to offer impedance
matching at the impedance of 50 Ω, which is the characteristic impedance
of the SMA connector at the input of the microstrip antenna.
In accordance to the resonance frequency of 10.47 GHz [11], the correspond-
ing wavelength λ0 is:
λ0 =c
f0= 0.02865m = 28.65mm
where c is the light velocity (c∼ 3∗108m/s) and 10.47 GHz is the resonance
frequency of the transmitting antenna.
Initially all microstrips’ length were set to λ0/4.
Figure 3.6 shows the S11 parameter obtained by setting all microstrips’
length to λ0/4.
The radiation patterns of the antenna in the H plane is shown in Figure 3.7.
The radiation patterns of the antenna in the E plane is shown in Figure 3.8
. As is seen in Figure 3.7, the radiation pattern does not meet the
requirements of the project. Modifications are done to the microstrips’
3.3 Impedance Matching Network 26
Figure 3.6: S11 Parameter
Figure 3.7: Radiation Pattern H-plane
length in order to improve the performance of the antenna in terms
of radiation pattern. The microstrips’ length chosen for this design is
∼ λ0/4 and ∼ λ0/8. The theoretical values λ0/4 = 7.16mm and
λ0/8 = 3.58mm have been approximated to 7.5 mm and 4 mm accordingly.
The modifications are done after running many simulations in the CST
environment, varying one by one the microstrips’ length and evaluate the
result. These attempts to change the microstrips’ length have shown a
positive result in terms of radiation pattern of the receiving antenna.
The radiation pattern of the antenna after having modified the microstrips’
length is shown in Figure 4.9.
As seen in the Figure 3.9, for the first microstrip that should offer an
3.3 Impedance Matching Network 27
Figure 3.8: Radiation Pattern E-plane
impedance of 50Ω to the SMA connector, a width of 4.5mm and length
of 4mm ∼ λ0/8 has been chosen. The ramification that follows offers an
impedance of 100Ω and has a corresponding width of 2.4mm and length of
7.4mm ∼ λ0/4. The last ramification has a width of 1mm and length of
4mm ∼ λ0/8.
The parameter to intervene in order to modify the characteristic impedance
of the microstrip is the width of itself. This task has been facilitated by the
software used to design the antenna. The software CST MICROWAVE
STUDIO®∗ offers many facilities, like calculating the impedance of a
microstrip once set as variables the width and the εeff .
As shown in Table 3.1, the greater the characteristic impedance of the
microstrip, the narrower the width. The microstrips’ width changes from
4.5mm, 2.4mm to 1mm.
This problem is commonly encountered while designing microstrip antennas.
The impedance at the input of the patch varies with the position the
microstrip is placed. The more decentralized the microstrip that feeds
the patch is, the greater the impedance is. Due to this fact, sometimes
it becomes difficult to obtain physically realizable microstrips’ width.
∗http://www.cst.com/Content/Products/MWS/Overview.aspx
3.3 Impedance Matching Network 28
Fig
ure
3.9:
Rec
eivin
gA
nte
nna
Dim
ensi
ons
3.3 Impedance Matching Network 29
Width Length
50 Ω microstrip 4.5 mm 4 mm
1st ramification microstrip 2.4 mm 7.5 mm
2nd ramification microstrip 1 mm 4 mm
Table 3.1: The width and impedance characteristic of microstrips
Therefore it usually is preferred to have the microstrip that feeds the patch
at the center other than close to the border of the patch.
C h a p t e r 4
Results and Discussion
In this chapter, the theoretical and measured results of the receiving
antenna array are discussed. For designing the patch array antenna, a
commercial software called CST MICROWAVE STUDIO®∗ is used. This
designing environment allows designing and investigating of corresponding
parameters of Radio Frequency (RF) components. The parameters highly
important to this antenna are investigated including the S11 parameter and
the radiation patterns in both planes, accordingly the E-plane and the H-
plane. Afterwards, the results of the same parameters which are measured in
the laboratory are shown. It is proceeded on the discussion and comparing
of the above mentioned parameters.
4.1 Parameters Statement
The final antenna design dimensions lead from the theoretical evaluations
done in Chapter 4. Further interest is shown to the highly practical need
for the antenna to be put in the runner’s chest. Therefore, the ground plane
dimension should be appropriate with regard to this shrewdness.
The final antenna dimensions are:
Lground = 130mm
Wground = 60mm
Lpatch = 13mm
Wpatch = 8mm
d = 5mm
∗http://www.cst.com/Content/Products/MWS/Overview.aspx
4.1 Parameters Statement 31
The working frequency of the receiving antenna, in accordance with the
transmitting one, is ≈ 10.47GHz. For the simulations, a frequency range
that goes from 8 GHz to 12 GHz is explored. The parameters under
investigation are the S11 and the radiation pattern. The S11 parameter
is an element of the scattering matrix, which quantifies how RF energy
propagates through a multi-port network. For a RF signal incident on one
port, some fraction of the signal bounces back out of that port, some of it
scatters and some of it transforms as heat. The S11 parameter refers to the
ratio of the signal that reflects from port one to the incident signal on port
one, thus it is seen as the reflection coefficient at the port that feeds the
antenna. The S parameter magnitude in linear scale is converted in to the
logarithmic scale according the formula:
S11 = 20 log[S11(magnitude)] (4.1)
The radiation pattern or the far field pattern refers to the directional
(angular) dependence of the strength of the radio waves from the antenna.
This parameter tells how the electromagnetic field is in the far field. The
far field generally is taken at a distance greater than 2D2/λ, where D is the
greater dimension of the antenna, and λ is the wavelength.
2D2/λ = 2(0.13m)2/0.0286m ≈ 1.18m (4.2)
4.1.1 Simulated Parameters
The simulated S11 parameter by means of the CST MICROWAVE STUDIO®
environment is shown in Figure 4.1:
This parameter is investigated within the frequency range [8 GHz-12 GHz].
Since the S11 parameter represents the reflected portion of the signal sent
to the antenna, the lower the S11 is, the better the performance of the
antenna is. As depicted in Figure 4.1, the S11 behaves good within the range
≈ [9.5GHz − 10.5GHz]. Therefore, the antenna shows a good adaption
within a range of ≈ 1GHz. This is a good result for this type of antenna,
4.1 Parameters Statement 32
Figure 4.1: Simulated S11 parameter
which at most offers a bandwidth of 20%.
The simulated radiation pattern in the H plane is shown in Figure 4.2
Figure 4.2: Simulated radiation pattern: H plane
While in Figure 4.3 the radiation pattern in the E plane is shown
The parameters of the radiation pattern should meet some requirements the
application needs. In this case, the Angular Width at 3 dB should not be
excessive, either narrow. The Side Lobe Level represents the ratio of the
main lobe to the secondary lobe. The lower the Side Lobe Level, the better
the performance of the antenna.
The simulated results are as follows:
4.1 Parameters Statement 33
Figure 4.3: Simulated radiation pattern: E plane
• Main lobe magnitude= 10.8 dBi
• Main lobe direction= 0.0 °
• Angular width (3 dB)= 19.4 °
• Side lobe level= -7.7 dB
In order to better figure out the orientation in the space of the electromag-
netic field, a 3D image of the far-field is shown in Figure 4.4
Figure 4.4: 3D view of far-field
4.1 Parameters Statement 34
4.1.2 Measured Parameters
All the parameters above exposed, have been measured within the antenna
laboratory. The techniques and the equipment used to make these
measurements are shown.
S11 Parameter Set-Up
In order to experimentally evaluate the S11 parameter of the receiving
antenna, a network analyzer Agilent 8510 is used. For a start, the calibration
of the network analyzer is done by connecting three different loads by means
of a coaxial cable.
The loads considered are:
• Short circuit load
• Open circuit load
• Matched load at 50 Ω
The calibration is a comparison between measurements, one of known
magnitude of correctness set with one device. Once the calibration is over,
the receiving antenna is connected to the coaxial cable. The frequency range
set is the same as the one set in the simulation with the CST Microwave
Studio, [8 GHz-12 GHz].
The measured S11 parameter is shown in Figure 4.5
The course of the S11 is almost the same. The measured S11 parameter
behaves better than the simulated one. This can be noticed by the downward
shift the S11 has experienced. There is also a right shift of the course of the
S11 of ≈ 200MHz as seen in Figure 4.6
4.1 Parameters Statement 35
Figure 4.5: Measured S11 parameter
Figure 4.6: S11 parameter: Comparison
Radiation Pattern: Set-Up
In order to evaluate the experimental radiation pattern of the receiving
antenna, the following set-up has been followed: A signal generator
generates a signal at the desired frequency. This signal is modulated at
1 KHz and sent to the antenna. Once the receiving antenna receives the
signal, the demodulation takes place. The demodulated signal is stored on
a computer. The receiving antenna is placed on a rotating plane while the
measurements takes place. This is done in order to explore 360 of the
4.1 Parameters Statement 36
radiation pattern.
The devices used for running this measurement are:
• Signal Generator (HP8620C): generates a signal at 10.47GHz of
frequency, modulated at 1KHz
• Network Analyzer: verifies the frequency the generated signal has
• Crystal diode (HP8470B): directly connected to the receiving antenna,
provides the voltage as output signal which is proportional to the
signal’s power in input
• Selective voltmeter (HP3581C): measures the root mean square (rms)
of the received signal at the frequency of the modulating signal
(1KHz)
• Acquisition board (NI PCI 6220): acquires the voltage signal obtained
by the selective voltmeter
• Absorbing cones
The devices are connected to each others as in Figure 4.7
Figure 4.7: Radiation Pattern: Set-Up
The positioning of the receiving antenna in the antenna laboratory sur-
rounded by the absorbing cones is shown in Figure 4.8
4.1 Parameters Statement 37
Figure 4.8: Rx antenna
The resulting data obtained by the measurement process is acquired by
the LabView Signal Express software and further processed by MATLAB®
2011a in order to obtain the final radiation pattern.
The radiation pattern of the receiving antenna in the H-plane obtained by
the measurement is seen in Figure 4.9
Figure 4.9: Radiation Pattern: H plane
It is useful to compare the simulated and the measured radiation patterns
in order to figure out the if there have been any improvement or not on the
4.1 Parameters Statement 38
antenna performance.
The radiation patterns in the H-plane are compared as seen in Figure 4.10
Figure 4.10: Radiation Patterns Comparison: H plane
The radiation pattern of the antenna in the E plane is seen in Figure 4.11
The radiation patterns in the E-plane instead, are seen in Figure 4.12
Detailed measurements are shown in Table 4.1
E plane H plane
Angular Width (3 dB) simulated 54 deg 19.4 deg
Angular Width (3 dB) measured 51 deg 22 deg
Side Lobe Level (simulated) -18.7 dB -7.7 dB
Side Lobe Level (measured) -15.4 dB -14 dB
Table 4.1: Detailed measurements
4.1 Parameters Statement 39
Figure 4.11: Radiation Pattern: E plane
Figure 4.12: Radiation Patterns Comparison: E plane
Antenna Gain Set-Up
The gain of the antenna is measured as well as the other parameters in the
antenna laboratory. For this measurement, the devices that have been used
4.1 Parameters Statement 40
are:
• signal generator
• absorbing cones
• variable attenuator
• power meter
The power meter device let us observe the signal power strength that
is received by the antenna. The attenuator instead, is used during the
calibration process of the delivered power.
In order to determine the receiving antenna gain, two antennas are used.
One of these antennas is the one whom parameters are known. This antenna
is the transmitting one in this context. The other one is the receiving
antenna we want to measure the gain. It’s parameters are not known. These
two antennas are placed at a distance of 3m. The distance chosen is greater
than the distance the far-field region of the receiving antenna starts.
The transmitting antenna is connected to the signal generator, while the
receiving one is connected to the power meter. This allows to visualize by
means of the power meter the power received by the receiving antenna.
The signal generator generates a signal at 10.47GHz of frequency, with a
signal power of 8.5 dBm. The transmitting antenna has a known gain of
19.7 dB. The power meter device visualizes a received signal power strength
of -22 dBm.
By applying the Friis Transmission Equation, the receiving antenna gain
can be calculated:
Pr = PtGtGr(λ0
4πr)2 (4.3)
The available known data we have are:
4.1 Parameters Statement 41
Pt = 8.5dBm
Pr = −22dBm
Gt = 19.7dB
λ ≈ 0.028m
r = 3m
The only unknown variable in this equation is the receiving antenna gain Gr.
The variables of the equation are expressed in logarithmic scale, therefore
the equation modifies as:
Pr |dBm= Pt |dBm +Gt |dB +Gr |dB +((λ0
4πr)2) |db (4.4)
Therefore, the receiving antenna gain is:
Gr |dB= Pr |dBm −Pt |dBm −Gt |dB −((λ0
4πr)2) |dB (4.5)
Gr |dB= −22dBm− 10dBm− 19.7dB − (−62.5791dB) ≈ 11.8dB (4.6)
Antenna gain
Simulated 14 dB
Measured 11.8 dB
C h a p t e r 5
Signal Acquisition and Processing
This chapter focuses on the received signal and its processing. A detailed
study of the received signal has been done considering many factors such
as the radiation patterns of the antennas (transmitting and receiving one),
and the distance and position the antennas are placed.
5.1 Overview of the Received Signal
The level of the received signal by the microstrip antenna is very important.
The good knowledge of the phenomena that influence the signal quality
facilitate and made more comprehensive the whole situation.
In order to analyze the received signal, the well-known Friis Transmission
Equation that gives the received power, once the transmitted power is a
known amount is used:
Pr = PtGtGr(λ0
4πr)2 (5.1)
where Pt is the transmitted power, Gt is the transmitting antenna gain, Gr
is the receiving antenna gain, λ0 is the wavelength, and r is the distance the
antennas are placed.
Once Pr is calculated, the corresponding output voltage can be computed
by the formula:
Vout =√PrZ0 (5.2)
5.1 Overview of the Received Signal 43
where Z0 = 50Ω is the characteristic input impedance, the same impedance
the SMA connector offers to the receiving antenna. In the calculations, the
transmitted power is assumed to be 1Watt. Gt and Gr of the transmitting
and receiving antennas are known, as well as the working frequency.
The distance r used within the Friis Equation is computed considering
different situations:
(1) Situation 1: The transmitting and the receiving antenna are situated
in the same horizontal plane: (x− z) plane with regard to the reference
system chosen for the antennas.
(2) Situation 2: The transmitting and the receiving antennas are not
anymore positioned in the same horizontal plane. The transmitting
antenna is moved in the vertical plane, above and below the height of
the receiving antenna.
(3) Situation 3: The receiving antenna is rotated around the x axis.
The result analysis of mentioned situations are described in detail in the
following
(1) Situation 1: The first case offers the possibility to explore the simpler
situation: the antennas distance varies as it varies the position of one
of the antennas with regard to the other one. This way, the considered
coordinates are determined by moving the receiving antenna along x
and z axes. For the z axis, the receiving antenna has been moved from
2m to 5m with a step of 0.5m. For the x axis are considered coordinates
from 0m to 1m with a step of 5cm.
Figure 5.1 shows how Vout signal amplitude changes as the receiving
antenna is moved along the X axis and along Z axis. At the beginning,
the antennas lie along the Z axis which is perpendicular to (x − y)
plane. At this point, x is considered to be equal to 0. This means that
the receiving antenna is completely invested by the electromagnetic field
of the transmitting antenna which has created the electromagnetic wall.
There are 7 graphs in Figure 5.1, each of them is computed by shifting
the receiving antenna along an axis which is parallel to the x axis and
5.1 Overview of the Received Signal 44
Figure 5.1: Vout versus X axis while varying the distance
the distance between these axes varies from 2 to 5 m with a step of 0.5
m.
The bigger the initial distance between the antennas is, the lower the
Vout signal amplitude is. Another feature of the signal is the fact that
the bigger the distance between the antennas is, the slower the signal
amplitude falls. Even though the slope of the graphs is different, for a
certain shift of the receiving antenna along the x axis, the Vout signal
amplitude becomes almost the same for all cases. For a shift of the
antenna of around 30 cm, all the graphs start having the same course.
As the shift increases, all signals drops significantly.
Figure 5.1 is useful to set the thresholds the warning system needs to
activate the transducers. Particular attention should be paid to the
values of the thresholds. Once a certain value is set, this means that
if the signal strength is higher than that value, the transducers are
activated and the vibration takes place. If the signal strength is lower,
the transducers cannot be driven and no warn will be sent to the runner.
The setting of the threshold should take into account what shift along
the x axis corresponds to that Vout signal amplitude. This evaluation
is important, because the runner should have the appropriate time and
space to react on time to the warning sent by the transducers.
(2) Situation 2: The second case explores not only the horizontal (x− z)
5.1 Overview of the Received Signal 45
plane, but also the vertical one (x− y). Coordinates with a step of 5cm
for the y axis in the range of [−20cm÷ 20cm] are considered.
Figure 5.2: Vout versus X axis while varying the height
Figure 5.2 shows how the Vout signal amplitude changes while changing
the height of the receiving antenna. The receiving antenna is shifted
along the Y axis.
In Figure 5.2, there are 5 graphs showing 5 different situations. When
y>0, the receiving antenna is downward shifted with regard to the
transmitting one, and vice-versa. The deviation of the curves from
the reference one (y = 0) is bigger for small shift of the antenna. This
deviation vanishes as the shift of the receiving antenna becomes larger.
(3) Situation 3: The last study case is referred to the situation where the
receiving antenna is rotated around the x axis. This case comes up as
we think about the wearable antenna the runner has on the chest and
the attitudes the runner has. It is well known that runners start their
race forward bent in order to minimize the resisting force of the wind.
This leads to a rotation of the receiving antenna around the x axis.
However, the angle of rotation is not excessive. It might vary up to 30°.
Figure 5.3 illustrates what happens to the Vout signal strength if the
receiving antenna is rotated by 20° around the x axis.
5.2 Signal Acquisition and Processing System Components 46
Figure 5.3: Vout versus X axis while rotating around X axis
The curves have a smaller slope, thus they start getting together and follow
the same course for bigger shift of the antenna along the x axis. This
might influence the warning system. The runner gets warned sooner. This
is because the signal drops slowly, thus the signal amplitude is above the
threshold for a longer period of time. The time the runner is bent forward
is relatively short, thus this doesn’t affect significantly the warning system.
5.2 Signal Acquisition and Processing Sys-
tem Components
In order to accomplish the requirements set by the electromagnetic system,
the signal has been processed.
Once received, the signal is demodulated and amplified. The amplification
takes place inside the demodulation module. The output signal of this
module will be filtered by two BandPass filter at the corresponding
frequencies of 1 kHz and 11.3 kHz. This makes possible to distinguish
and figure out which transmitting antenna has transmitted the signal. The
following module is the rectifier. Within the MCU (MicroController Unit)
module the AD signal processing will take place. Signal thresholds are set.
When the signal strength in input at the MCU module is higher than the
5.2 Signal Acquisition and Processing System Components 47
Fig
ure
5.4:
Rec
eivin
gSubsy
stem
:P
roce
ssin
gof
the
Sig
nal
5.3 Amplification and Demodulation of the Signal 48
threshold, the transducers will vibrate. One of the thresholds is set in order
to aware the runner that is getting closed to the lane border. This allows the
runner to have a first information about the route. The second threshold
is set to aware the runner that is running almost out of the border of the
lane. The two step warning system to the runner is considered safer, and
it gives time to the runner to react on time in order to change the route in
accordance to the information received.
5.3 Amplification and Demodulation of the
Signal
The signal amplitude received by the array antenna is low, i.e, the received
signal amplitude cannot be directly demodulated and processed by the
MCU. Therefore, the signal needs to be amplified. This task is performed
within the printed board used to demodulate the signal AM modulated in
transmission.
5.3.1 Amplification and Demodulating Board
For this purpose, LTC5582 1528A printed circuit is used. The 1528A
circuit is a Mean-Squared Power Detector featuring the LTC® 5582 IC [14].
The LTC5582 is a wide dynamic range Mean Squared RF Power Detector,
operational from 40 MHz to 6GHz. The input dynamic range with ±1dB
nonlinearity is 60 dB depending on frequency (from -58dBm to +2dBm,
single-ended 50 Ω input). The detector output voltage slope is normally
30mV/dB, and the typical output variation over temperature is ±0.5dB
at 2140 MHz. The DC1528A Demo Circuit is optimized for wide frequency
range of 40 MHz to 5.5 MHz. However, input match can be optimized above
6 GHz with simple external matching. Operating above 6 GHz is possible
with reduced performance.
The typical values of the parameters are shown in Table 5.1
5.3 Amplification and Demodulation of the Signal 49
Parameter Condition Value
Supply Voltage 3.1V to 3.5V
Supply Current 41.6mA
Shutdown Cur-rent
EN=Low 0.1µA
Input FrequencyRange
Operation over wider frequencyrange with reduced performance
40MHz to10GHz
Table 5.1: Typical values of the parameters
Typical performance summary:
• Vcc=3.3 V
• EN=3.3 V
• TA = 25C
Some application notes to be taken into account are shown in Table 5.2
Supply voltage 3.8V
Enable voltage -0.3V to Vcc +0.3V
Input signal power (single-ended, 50Ω) 18 dBm
Input signal power (differential, 50 Ω) 24 dBm
Operating temperature range −40C to 85C
Table 5.2: Absolute Maximum Ratings
The LTC5582 1528A printed circuit is shown in Figure 5.5
LTC5582 Board
The LTC® 5582 is a 40 MHz to 10 GHz RMS responding power detector [15].
It is capable of accurate power measurement of an AC signal with wide
5.3 Amplification and Demodulation of the Signal 50
Figure 5.5: LTC5582 1528A RMS Power Detector
dynamic range, from -60 dBm to 2 dBm depending on frequency. The power
of the AC signal is an equivalent decibel-scaled value precisely converted into
DC voltage on a linear scale. This board produces in output a quantity of
voltage as a result of applying to it in input a certain power.
Figure 5.6: Output Voltage vs RF Input Power
The curves presented in the graph show the output voltage versus the input
5.3 Amplification and Demodulation of the Signal 51
power at different environmental temperatures. To be noticed that all
the performance characteristics below exposed are measured at the room
temperature of TA = 25C. It is seen in Figure 5.6 that for an input power
between ≈[−40dBm ÷ +5dBm] range, the curves increase linearly. This
means that the output voltage has a linear relationship to the input power.
The LTC5582 board is suitable for precision RF power measurement and
level control for a wide variety of RF standards, including LTE, WiMAX,
W-CDMA, CDMA2000. TD-SCDMA, and EDGE. The part is packaged in
a 10-lead 3mm x 3 mm.
Some of the most important features of the integrated circuit are:
• Frequency Range: 40 MHz to 10 GHz
• Linear Dynamic Range: Up to 57 dB
• Accurate RMS Power Measurement of High Crest Factor Modulated
Waveforms
• Exceptional Accuracy Over Temperature: ±0.5dB
• Low Linearity Error within Dynamic Range
• Single-Ended or Differential RF Inputs
• Fast Response Time: 90ns Rise Time
• Low Supply Current: 41.6 mA at 3.3 V
• Small 3 mm x 3 mm
The board can be used for other purposes. Some of these applications are:
• PA Power Control
• Receive and Transmit Gain Control
• Point-to-Point Microwave Links
• RF Instrumentation
5.3 Amplification and Demodulation of the Signal 52
Figure 5.7: Top View of LTC5582 board
The LTC5582 pinout is shown in Figure 5.7
Even though the board offers excellent performance according to the data
sheet for frequencies up to 5.5 GHz, in this case the board is used at
frequencies up to ≈ 10.47GHz. The performance has suffered significant
changes, and the signal amplitude we obtain is significantly smaller with
regard to the one shown in the data sheet for frequencies up to 5.5 GHz.
Nevertheless, no change has been done to the input matching network as
recommended by the data sheet of the board, because the signal amplitude
is adequate for our tests.
This board produces a square wave output, whose amplitude is proportional
to the voltage. The square wave will be processed by an electronic circuit.
The purpose of this circuit is to elaborate the square wave, define two
BandPass filters and based on the information carried by the wave, set two
thresholds. The two BandPass filters are set in order to figure out which
transmitting antenna has been sending the signal. The receiving antenna is
under the electromagnetic field of both transmitting antennas. Therefore,
the signal received by the antenna is the sum of two signals. In all real
situations, one of the signal predominates over the other one. At this point,
the filters help distinguishing between them.
The thresholds are set based on the amplitude of the square wave instead.
The closer the runner is to the lane’s border, the bigger the amplitude.
5.3 Amplification and Demodulation of the Signal 53
The first set threshold, activates the transducer to vibrate as the runner
gets closer to the lane’s border. This is a first forewarn sent to the runner.
The second threshold needs a higher signal amplitude to be activated and
drive the transducer. This happens if the runner keeps following the same
route even after having been informed he/she is getting closer to the border.
The signal strength gets bigger and the second threshold activates the
transducer.
The way the transducers warn the runner might be different. One of these
increases the amount of vibration as the runner gets closer to the border.
The other one activates more transducers as the signal’s strength increases.
C h a p t e r 6
Conclusions and Future Work
Conclusions
This master thesis project deals with an electromagnetic system supporting
visually impaired runners. It is to be considered successive to a previous
project [11] which dealt with the design of the transmitting antenna. The
goal of the project is to design a receiving wearable antenna that the athlete
will put on his chest.
Factors such light weight, small dimensions, low cost, and electromagnetic
safety have influenced the choice of the antenna. These requirements are
fulfilled by a microstrip antenna.
In the following step which consists on designing the antenna, parameters
such as the S11 and the radiation pattern are taken into account. These
requirements the receiving antenna has to meet partly derive by the features
the transmitting antenna has.
In particular, both transmitting and receiving antennas have to resonate
at the same frequency. The radiation pattern instead, is dictated by a
preliminary evaluation of the received signal.
Once all the performance evaluations are done, the antenna is built. The
antenna is shown to meet all the requirements of the project. Further more,
detailed studies are made on the received signal which has led to better
accurate the electronics used for the signal processing and the warning unit.
Since visually impaired athletes’ needs claim further research attention with
regard to the visually impaired people who are not engaged in any kind of
sport activities, the traditional solutions no longer meet the needs they have.
As the attitude of the sport activities toward the visually impaired athletes
has changed, their needs have changed as well.
• Innovative supporting systems are needed by the athletes. It is totally
impractical to make use of other senses like the hearing to have
55
a feedback information by these supporting systems, since visually
impaired people rely and empower this sense very much. It is also
counterproductive to make use of the hands, because of the key role
they have when talking about sport.
The system is a free-hand one, and does not make use of the hearing
sense. It makes use of the arm for having a vibration feedback by the
system.
Therefore, the electromagnetic system inhere designed overcomes
these issues.
• Many of the existing electromagnetic systems require a high computa-
tional power, which leads to a heavy equipment the athlete has to carry
on during the training and/ or during the races. Therefore, the other
advantage this system provides is the low-weight all the components
the system consist of has.
• It is important to notice that the electromagnetic system inhere
proposed is not expensive. The athletes that usually run the races, are
more disposed to invest in innovative supporting systems that might
help them achieve the results they are willing to. Generally, this is
not the case for the visually impaired people who find themselves
everyday engaged on some kind of sport activity like the athletics,
and who would like to make use of the innovative systems as well, but
cannot afford the cost.
• The system proposed in this master project is a fast-processing signal
system, which undoubtedly leads to a reliable system.
Most of visually impaired people find difficult to deal with innovative
supporting equipment because of the complex technology involved
within. Often such an equipment requires the user to have a certain
familiarity with many aspects of the that technology in order to make
it work.
Many supporting equipment success rely on the easy approach of use
they offer. A psychologically acceptable equipment allows the user to
fully take advantage of the potentiality it offers.
56
Future Work
The future work on this electromagnetic system might concentrate on
studying the most appropriate way of placing the two transmitting antennas
which lead the runner. It is not determined yet if these antennas should be
placed on some vehicle, or some ad hoc machine.
The choice might influence the quality of the signal received by the antenna
placed on the runner’s chest. The height the transmitting antennas are
placed with regard to the height of the receiving one, influences the signal
amplitude which might vary considerably. This argument leads to have a
machine able to vary the height the antenna is positioned in accordance to
the runners’ stature.
Once this issue is fixed, athletes should be able to fully be confident and
feel comfortable with this electromagnetic system.
The optimistic result leads to further investigate and invest in innovative
ideas regarding user-friendly supporting electromagnetic systems.
Bibliography
[1] I. Ulrich and J. Borenstein, “The guidecane-applying mobile robot
technologies to assist the visually impaired,” Systems, Man and
Cybernetics, Part A: Systems and Humans, IEEE Transactions on,
vol. 31, no. 2, pp. 131–136, 2001.
[2] “Visual impairment and blindness,” June 2012. [Online]. Available:
http://www.who.int/mediacentre/factsheets/fs282/en/
[3] “Low-vision aids,” 2012. [Online]. Available: http://www.
independentliving.com
[4] “Olympic charter,” February 2012. [Online]. Available: http://www.
olympic.org/Documents/Olympic%20Charter/Charter en 2010.pdf
[5] September 2012. [Online]. Available: http://www.london2012.com/
paralympics/athletics/about/
[6] “Paralympics 2012: the guide runners,” September
2012. [Online]. Available: http://www.telegraph.co.
uk/sport/olympics/paralympic-sport/paralympics-gb/9529080/
Paralympics-2012-the-guide-runners.html
[7] S. Shoval, I. Ulrich, and J. Borenstein, “Navbelt and the guide-
cane [obstacle-avoidance systems for the blind and visually impaired],”
Robotics & Automation Magazine, IEEE, vol. 10, no. 1, pp. 9–20, 2003.
[8] S. Cardin, D. Thalmann, and F. Vexo, “Wearable obstacle detection
system for visually impaired people,” in VR workshop on haptic and
tactile perception of deformable objects, 2005, pp. 50–55.
[9] A. N. A. Benjamin J. M., “A lase cane for the blind,” in San Francisco
Biomedical Symposium, 1973, pp. 53–57.
[10] A. Fusiello, A. Panuccio, V. Murino, F. Fontana, and D. Rocchesso,
“A multimodal electronic travel aid device,” in Multimodal Interfaces,
2002. Proceedings. Fourth IEEE International Conference on. IEEE,
2002, pp. 39–44.
BIBLIOGRAPHY 58
[11] M. Pieralisi, “Progettazione e realizzazione di antenne per un sistema
elettromagnetico di ausilio ad atleti con handicap visivi,” Master’s
thesis, Universita Politecnica delle Marche, 2012.
[12] C. A. Balanis, Antenna Theory. Jonh Wiley & Sons, Inc, 2005.
[13] C. W. J. R. James, P. S. Hall, Microstrip Antennas, Theory and Design.
The Institution of Electrical Engineers, London and New York, 1981.
[14] L. Technology, “Demo circuit 1528a quick start guide.” [Online].
Available: http://cds.linear.com/docs/Demo%20Board%20Manual/
dc1528A.pdf
[15] ——, “Ltc5582, 40 mhz to 10 ghz rms power detector with 57 db
dynamic range.” [Online]. Available: http://cds.linear.com/docs/en/
datasheet/5582f.pdf
A p p e n d i x A
Output Signal Strength
Evaluation Scripts
The strength of the output signal of the receiving antenna was evaluated
based on the data obtained from the simulation with CST. The evaluation
was performed by scripts written in MATLAB® 2011a. These scripts are
listed in the following
Initializing, importing simulation data, and calculate Prad
1 clear;
2 delta_theta=1*pi/180;
3 delta_phi=1*pi/180;
4 phi=0:delta_phi:2*pi;
5 theta=0:delta_theta:pi;
6 M=size(phi,2);
7 N=size(theta,2);
8 eta=377;
9 lambda=0.0289;
10
11 % first antenna
12 Etheta1=zeros(M,N);
13 Ephi1=zeros(M,N);
14 U01=zeros(M,N);
15 P01=zeros(M,N);
16
17 % 2nd antenna
18 Etheta2=zeros(M,N);
19 Ephi2=zeros(M,N);
20 U02=zeros(M,N);
21 P02=zeros(M,N);
22
23 % import data from text files
24 info_1 = importdata('info_1.txt');
25 file2_def = importdata('file2_def.txt');
26
27 for m=1:M
28 for n=1:N
29 p=(m-1)*N+n;
30 Etheta1(m,n)=info_1(p,3)+1i*info_1(p,4);
31 Ephi1(m,n)=info_1(p,5)+1i*info_1(p,6);
32 U01(m,n)=(1/(2*eta))*(abs(Etheta1(m,n))ˆ2+abs(Ephi1(m,n))ˆ2);
60
33 P01(m,n)=U01(m,n)*sin(theta(n))*delta_theta*delta_phi;
34
35 Etheta2(m,n)=file2_def(p,3)+1i*file2_def(p,4);
36 Ephi2(m,n)=file2_def(p,5)+1i*file2_def(p,6);
37 U02(m,n)=(1/(2*eta))*(abs(Etheta2(m,n))ˆ2+abs(Ephi2(m,n))ˆ2);
38 P02(m,n)=U02(m,n)*sin(theta(n))*delta_theta*delta_phi;
39 end
40 end
41 Prad1 = sum(sum(P01));
42 Prad2 = sum(sum(P02));
Evaluation of Vout while moving the receiving antenna along the
z axis: [2m- 5m] with a step of 0.5 m.
1 D1=(4*pi*U01)/Prad1;
2 D2=(4*pi*U02)/Prad2;
3
4 Pric = zeros(M,N,L);
5 D = D1 .* D2;
6 for l=1:L
7 Pric(:,:,l) = Ptras*(lambda/(4*pi*r(l)))ˆ2*D;
8 end
9
10 Vout = sqrt(Pric*50);
11
12 ColorOrder = get(gca, 'ColorOrder');
13 Ncol = size(ColorOrder,1);
14
15 idx90 = (90*pi/180)/delta_theta+1; % calculate the corresponding index of theta
=90
16 hold on;
17 for l=1:L
18
19 plot(theta(1:idx90)*180/pi,Vout(1,1:idx90,l),'Color', ColorOrder(mod(l,Ncol)
+1,:));
20
21 end
22
23 legs = arrayfun(@(x) sprintf('l = %0.1f m',x),r,'UniformOutput', false);
24 legend(legs);
25 xlabel('degree'); ylabel('Vout')
26 hold off;
Evaluation of Vout while moving the receiving antenna along the
x and z axes
1 Ptras=1;
2 D1=(4*pi*U01)/Prad1;
3 D2=(4*pi*U02)/Prad2;
4 D1_2 = D1 .* D2;
61
5
6 fix_phi = 0; % degree
7 idx_fix_phi = (fix_phi*pi/180)/delta_phi + 1;
8
9 %% Calculate and plot with theta and r with phi = 0
10 Pric1 = zeros(N,L);
11 for l=1:L
12 Pric1(:,l) = Ptras*(lambda/(4*pi*r(l)))ˆ2*D1_2(idx_fix_phi,:)';
13 end
14
15 Vout1 = sqrt(Pric1*50);
16
17 %% Plot Vout against theta
18 ColorOrder = get(gca, 'ColorOrder');
19 Ncol = size(ColorOrder,1);
20
21 idx90 = (27*pi/180)/delta_theta+1; % calculate the corresponding index of theta
=27
22 mfig('Plot Vout against theta with differnt value of r (phi=0)');clf;hold;
23 for l=1:L
24 plot(theta(1:idx90)*180/pi,Vout1(1:idx90,l),'Color', ColorOrder(mod(l,Ncol)
+1,:));
25 end
26 legs = arrayfun(@(x) sprintf('r = %0.1f m',x),r,'UniformOutput', false);
27 legend(legs);
28 xlabel('theta (degree)'); ylabel('Vout')
29
30
31 %% Calculate and plot with h and d with phi = 0
32 h=2:0.5:5;
33 d=0:0.05:1;
34 H=size(h,2);
35 D=size(d,2);
36 theta_angles=zeros(H,D);% in degree
37 rs=zeros(H,D);
38 Pric2=zeros(H,D);
39
40 for i=1:H
41 for j=1:D
42 angle_radian = atan((d(j))/h(i));
43 angle_degree = angle_radian*180/pi;
44 theta_angles(i,j) = round(angle_degree);
45 rs(i,j) = sqrt(h(i)ˆ2 + d(j)ˆ2);
46 end
47 end
48
49 % Vout = zeros(H,D,N);
50 for i=1:H
51 for j=1:D
52 angle_radian = atan((d(j))/h(i));
53 index_theta = round(angle_radian/delta_theta)+1;
54 Pric2(i,j) = Ptras*(lambda/(4*pi*rs(i,j)))ˆ2*D1_2(idx_fix_phi,
index_theta);
55 end
56 end
62
57 Vout2=sqrt(Pric2*50);
58
59 % Plot Vout against d
60 ColorOrder = get(gca, 'ColorOrder');
61 Ncol = size(ColorOrder,1);
62 mfig('Plot Vout against d with different values of h (phi=0)');clf;hold;
63 for i=1:H
64 plot(d,Vout2(i,:),'Color', ColorOrder(mod(i,Ncol)+1,:));
65 end
66 legs = arrayfun(@(x) sprintf('h = %0.1f m',x),h,'UniformOutput', false);
67 legend(legs);
68 xlabel('d'); ylabel('Vout');
69
70 % Plot Vout against d
71 mfig('Plot Vout against theta with different values of h (phi=0)');clf;hold;
72 for i=1:H
73 plot(theta_angles(i,:),Vout2(i,:),'Color', ColorOrder(mod(i,Ncol)+1,:));
74 end
75 legs = arrayfun(@(x) sprintf('h = %0.1f m',x),h,'UniformOutput', false);
76 legend(legs);
77 xlabel('theta (degree)'); ylabel('Vout');
Evaluation of Vout while varying the height of one of the antennas
along the y axis
1 %% Calculate and plot with h, d, and t
2 t=-0.2:0.1:0.2;% y : t > 0 when rx is lower than tx
3 %t=-0.3:0.05:0; % y: t < 0 when rx is higher than tx
4 h=2:0.5:5; % z
5 d=0:0.05:1; % x
6 %d=d+eps;
7 T=size(t,2);
8 H=size(h,2);
9 D=size(d,2);
10 theta_angles=zeros(H,D);% in degree
11 phi_angles=zeros(D,T);% in degree
12 rs=zeros(H,D,T);
13 Pric2=zeros(H,D,T);
14
15 for i=1:H % z
16 for j=1:D % x
17 for k=1:T % y
18 angle_radian_theta = atan2(d(j),h(i));
19 angle_degree_theta = angle_radian_theta*180/pi;
20 theta_angles(i,j) = round(angle_degree_theta);
21 angle_radian_phi = atan2(t(k),d(j)) ;
22 % in case phi < 0, we should take the complement angle
23 % e.g. if phi = - pi/3, indeed, the angle from x toward y should be
24 % 2*pi + phi = 2*pi - pi/3 = 5*pi/3
25 if (angle_radian_phi <0)
26 angle_radian_phi = 2*pi+angle_radian_phi;
27 end
28 angle_degree_phi = angle_radian_phi*180/pi; % radians to degree
63
29 phi_angles(j,k) = round(angle_degree_phi);
30
31 rs(i,j,k) = sqrt(h(i)ˆ2 + d(j)ˆ2 + t(k)ˆ2) ;
32 end
33 end
34 end
35
36 for i=1:H %z
37 for j=1:D %x
38 for k=1:T %y
39 angle_radian_theta = atan2(d(j),h(i));
40 angle_radian_phi = atan2(t(k),d(j));
41 index_theta_rx = round(angle_radian_theta/delta_theta)+1;
42 index_theta_tx = round(angle_radian_theta/delta_theta)+1;
43 % in case phi < 0, we should take the complement angle
44 % e.g. if phi = - pi/3, indeed, the angle from x toward y should be
45 % 2*pi + phi = 2*pi - pi/3 = 5*pi/3
46 if (angle_radian_phi >=0)
47 index_phi_rx = round(angle_radian_phi/delta_phi)+1;
48 else
49 index_phi_rx = round((2*pi+angle_radian_phi)/delta_phi)+1;
50 end
51
52 index_phi_tx = round((pi-angle_radian_phi)/delta_phi)+1;
53
54
55 Pric2(i,j,k) = Ptras*(lambda/(4*pi*rs(i,j,k)))ˆ2*D1(index_phi_tx,
index_theta_tx)*D2(index_phi_rx,index_theta_rx);
56 end
57 end
58 end
59 Vout2=sqrt(Pric2*50);
60
61 % Plot Vout against h and d
62 ColorOrder = get(gca, 'ColorOrder');
63 Ncol = size(ColorOrder,1);
64 %% mfig('Plot Vout against h and d with different values of t');clf;
65
66 [dg,hg]=meshgrid(d,h);
67 fig = mesh(dg,hg,Vout2(:,:,1));
68 xlabel('d'); ylabel('h'); zlabel('Vout');
69 set(fig, 'FaceColor',ColorOrder(mod(1,Ncol)+1,:), 'FaceAlpha',0.5, 'EdgeAlpha',
0);
70 hold on;
71 fig = mesh(dg,hg,Vout2(:,:,k));
72 set(fig, 'FaceColor',ColorOrder(mod(k,Ncol)+1,:), 'FaceAlpha',0.5, '
EdgeAlpha',0);
73
74 legs = arrayfun(@(x) sprintf('t = %0.2f m',x),t,'UniformOutput', false);
75 legend(legs);
76 hold off;
77
78 for j=1:H
79 mfig(sprintf('h=%0.2fm',h(j)));clf;hold;
80 for k=1:T
64
81 plot(d,Vout2(j,:,k),'Color', ColorOrder(mod(k,Ncol)+1,:));
82 end
83 legs = arrayfun(@(x) sprintf('t=%0.2f m',x),t,'UniformOutput', false);
84 legend(legs);
85 end
Evaluation of Vout while rotating the receiving antenna around x
axis
1 Ptras=1;
2 D1=(4*pi*U01)/Prad1;
3 D2=(4*pi*U02)/Prad2;
4 %% Calculate and plot with h, d, and t
5 t=-0.2:0.1:0.2;% y : t > 0 when rx is lower than tx
6 %t=-0.3:0.05:0; % y: t < 0 when rx is higher than tx
7 h=2:0.5:5; % z
8 d=0:0.05:1; % x
9 %d=d+eps;
10 T=size(t,2);
11 H=size(h,2);
12 D=size(d,2);
13 theta_angles=zeros(H,D,T);% in degree
14 phi_angles=zeros(H,D,T);% in degree
15 rs=zeros(H,D,T);
16 Pric2=zeros(H,D,T);
17 alpha=pi/18;% rotation angle
18
19 for i=1:H % z
20 for j=1:D % x
21 for k=1:T % y
22 angle_radian_phi = atan2(t(k),d(j));
23 % in case phi < 0, we should take the complement angle
24 % e.g. if phi = - pi/3, indeed, the angle from x toward y should be
25 % 2*pi + phi = 2*pi - pi/3 = 5*pi/3
26 if (angle_radian_phi <0)
27 angle_radian_phi = 2*pi+angle_radian_phi;
28 end
29 angle_degree_phi = angle_radian_phi*180/pi; % radians to degree
30 phi_angles(i,j,k) = round(angle_degree_phi);
31
32 angle_radian_theta = atan2(d(j),h(i));
33 angle_degree_theta = angle_radian_theta*180/pi;
34 theta_angles(i,j,k) = round(angle_degree_theta);
35
36 rs(i,j,k) = sqrt(h(i)ˆ2 + d(j)ˆ2 + t(k)ˆ2);
37 end
38 end
39 end
40
41 for i=1:H %z
42 for j=1:D %x
43 for k=1:T %y
44 angle_radian_phi = atan2(t(k),d(j));
65
45 angle_radian_theta = atan2(d(j),h(i));
46
47 angle_radian_phi_align = atan2((t(k)*cos(alpha)-h(i)*sin(alpha)),d(j));
48 angle_radian_theta_align = atan2(d(j),(t(k)*sin(alpha)+h(i)*cos(alpha)))
;
49
50 index_theta_rx = round(angle_radian_theta/delta_theta)+1;
51 index_theta_tx = round(angle_radian_theta_align/delta_theta)+1;
52 % in case phi < 0, we should take the complement angle
53 % e.g. if phi = - pi/3, indeed, the angle from x toward y should be
54 % 2*pi + phi = 2*pi - pi/3 = 5*pi/3
55 if (angle_radian_phi >=0)
56 index_phi_rx = round(angle_radian_phi/delta_phi)+1;
57 else
58 index_phi_rx = round((2*pi+angle_radian_phi)/delta_phi)+1;
59 end
60
61 index_phi_tx = round((pi-angle_radian_phi_align)/delta_phi)+1;
62 % index_theta_tx=round((alpha+angle_radian_theta_prev)/delta_theta)+1;
63
64 Pric2(i,j,k) = Ptras*(lambda/(4*pi*rs(i,j,k)))ˆ2*D1(index_phi_tx,
index_theta_tx)*D2(index_phi_rx,index_theta_rx);
65 end
66 end
67 end
68 Vout2=sqrt(Pric2*50);
69
70 for j=1:H
71 mfig(sprintf('h=%0.2fm',h(j)));clf;hold;
72 for k=1:T
73 plot(d,Vout2(j,:,k),'Color', ColorOrder(mod(k,Ncol)+1,:));
74 end
75 legs = arrayfun(@(x) sprintf('t=%0.2f m',x),t,'UniformOutput', false);
76 legend(legs);
77 end
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