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

s1049118@studenti.univpm.it

Master’s Thesis

Ancona - February 11, 2013

Supervisor: Prof. Graziano Cerri (g.cerri@univpm.it)

Polytechnic University of Marche

Co-supervisor: Ing. Paola Russo (paola.russo@univpm.it)

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