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UNIVERSITI PUTRA MALAYSIA
IMPROVED RECEIVER SYSTEM FOR LASER RANGE FINDER
SOODEH ZAHAB SANIEI
FK 2010 105
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IMPROVED RECEIVER SYSTEM FOR LASER RANGE FINDER
By
SOODEH ZAHAB SANIEI
Thesis Submitted to the School of Graduate Study, Universiti Putra Malaysia,
In Fulfilment of the Requirements of the Degree of Master of Science
May 2010
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DEDICATION
To
Presence of Imam zaman and My Beloved Leader
and
My family: Husband, Mother, and Father
For their endless support and love
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment
of the requirement of the degree of Master of Science
IMPROVED RECEIVER SYSTEM FOR LASER RANGE FINDER
By
SOODEH ZAHAB SANIEI
May 2010
Chairman: Dr. Ing. Ahmad Fauzi Abas
Faculty: Engineering
This thesis discusses on the design and development of Laser Range Finder receiver
for long range measurement application with concentration on Time of Flight (TOF)
concept for range estimation. In TOF method, a laser pulse is emitted from
transmitter through the target and the reflected pulse from the target would be
detected in pulse detector circuit of the receiver adjacent to the transmitter. By
measuring the time of flight of this pulse, the corresponding distance can be
obtained.
The designed receiver of this research has two major parts. First is pulse detector
circuit that is designed to operate with 50 ns pulse as the input, representing the
output of photo diode at receiver that will be provided by pulse generator in this
research. For variable sensitivity, which is necessary in long distance range finders,
the pulse detector circuit was designed based on variable offset strategy together with
variable detecting threshold instead of variable gain, as variable gain is more difficult
in control with complex circuitry. For short distance, in which the reflected signal is
less attenuated and background noise is stronger, the amount of added DC offset is
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higher (so the difference between main signal and threshold increases), and for long
distances it reduces gradually to zero. The main signal experiences variable offset
before passed to the comparator to be detected. This is a very important part resulting
in variable sensitivity in receiver. This signal will be compared to a variable
detecting threshold in comparator.
The variable threshold voltage in the comparator consists of three parts. The first
part produced by peak detector, is proportional to the amount of noise in the signal
to eliminate its effect in detection, which contributes towards more accurate
measurement. The second part is the output of low pass filter that acts as an
integrator, which is the baseline of the signal. Finally, the third part is a DC voltage
for eliminating the undesired voltages, which are the effects of inverter output (when
it is saturated) and variable offset, in the output of integrator. Applying this variable
threshold for reflected pulse detection results in reducing false detection and noise
and eliminate dc effects.
Another part of receiver is counter that is designed and developed using Field-
Programmable-Gated-Array (FPGA). FPGA does not only perform high accuracy
timing but converts the time to corresponding distance as well. The frequency of
operation is adjusted on 200 MHz. It means that the time intervals as short as 5 ns
can be measured resulting in a distance accuracy of 0.75 m, which is a good accuracy
for long distance measurement. The experimental results from pulse detector circuit
show that applying variable offset leads to variable sensitivity and variable detecting
threshold can reduce the effects of noise and DC offset in detection process. In
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addition, by implementing this method, the circuit will be much more simplified and
easy to control in comparison with common methods.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Master Sains
IMPROVED RECEIVER SYSTEM FOR LASER RANGE FINDER
Oleh
SOODEH ZAHAB SANIEI
May 2010
Pengerusi: Dr. Ing. Ahmad Fauzi Abas.
Fakulti: Kejuruteraan
Penyelidikan ini membincangkan reka bentuk dan perkembangan bagi penerima
pencari jarak laser untuk aplikasi pengukuran jarak jauh dengan penekanan konsep
perjalanan masa bagi anggaran jarak. Dalam kaedah perjalanan masa, denyut laser
dipancarkan daripada penghantar kepada sasaran dan denyut yang dipantulkan
daripada sasaran akan dikesan di litar pengesan denyut pada penerima berhampiran
penghantar. Jarak yang sama akan diperolehi dengan mengukur perjalanan masa bagi
denyut ini.
Bahagian pertama penerima iaitu litar pengesan denyut direka bentuk untuk
dikendalikan dengan 50 ns denyut sebagai input mewakili output fotodiod pada
penerima yang dibekalkan oleh penghasil denyut. Untuk kepekaan pembolehubah,
yang penting dalam pencari jarak yang jauh, direka bentuk berdasarkan strategi ofset
pembolehubah selain dari mendapat pembolehubah, kerana mendapat pembolehubah
lebih rumit dengan litar kompleks. Untuk jarak dekat, isyarat yang dipantul adalah
kurang lemah dan hingar latar belakang lebih kukuh, jumlah DC ofset bertambah
adalah lebih tinggi (jadi perbezaan antara isyarat utama dan ambang meningkat), dan
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untuk jarak jauh ia berkurang secara beransur-ansur kepada sifar. Jumlah bunyi
bising itu dalam isyarat boleh diukur dengan cekap dan kesannya akan dihapuskan,
yang menyumbang ke arah pengukuran lebih tepat. Isyarat utama, yang diperkuatkan
dan disongsangkan, akan mengalami ofset berubah-ubah sebelum hantar pembanding
yang akan dikesan dengan melebihi voltan ambang. Ini merupakan satu bahagian
penting memberi hasil dalam kepekaan pembolehubah dalam penerima.
Voltan ambang dalam pembanding terdiri daripada tiga bahagian. Bahagian pertama
adalah berkadaran untuk jumlah bunyi bising itu dalam fotodiod output. Selepas
menguatkan isyarat penerima daripada fotodiod, pengesan puncak menghasilkan
bahagian ini. Bahagian kedua adalah output turas laluan rendah yang berfungsi
sebagai pengamir, iaitu DC nilai isyarat selepas diterbalikkan. Akhir sekali,
bahagian ketiga adalah satu DC voltan untuk menghapuskan voltan yang tidak
diingini, yang merupakan kesan-kesan penyongsang output (apabila tepu) dan ofset
pembolehubah, dalam output pengamir. Aplikasi pelbagai ambang untuk pengesan
denyut mengurangkan pengesanan yang salah dan hingar, menghapuskan kesan DC
dan juga membolehkan ia mengesan dua objek serentak.
Bahagian lain penerima adalah yang direka bentuk dan dibangunkan dengan
menggunakan Field-Programmable-Gated-Array (FPGA). FPGA bukan sahaja
menjalankan masa kejituan tinggi tetapi (juga menukarkan) masa (kepada jarak
tertentu). Frekuensi operasi itu dilaraskan pada 200 MHz. Ia bermakna yang jarak-
jarak waktu sependek 5 ns dapat disukat yang menghasilkan satu ketepatan jarak
0.75 m, iaitu ketepatan yang bagus untuk pengukuran jarak panjang.
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ACKNOWLEDGEMENTS
First of all, I would like to express my greatest gratitude to ALLAH the almighty,
for his help and support during the course of life and moment of truth.
Special thanks to my supervisor, Dr. Ing. Ahmad Fauzi Abas for his advice and
guidance. His patience, frankness and encouragement helped me in the finishing this
work. Many thanks are also due to my committee member, Prof. Mohd Adzir Mahdi.
In the last but not least, the greatest support came from my family; my husband,
Mohsen; my Mother and Father; and my brothers, Ali and Hasan, for their endless
love and continuous mental help.
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I certify that an Examination Committee met on 13th
May 2010 to conduct the final
examination of SOODEH ZAHAB SANIEI on her master of Science thesis
entitled “DEVELOPMENT OF AN IMPROVED RECEIVER SYSTEM FOR
LASER RANGE FINDER” in accordance with Universiti Pertanian Malaysia
(Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree)
Regulations 1981. The committee recommends that the candidate be awarded the
relevant degree. Members of Committee are as follow:
MOHD ZAINAL ABIDIN AB KADIR, PhD
Department of Electrical and Electronics Engineering,
Faculty of Engineering,
Universiti Putra Malaysia.
(Chairman)
ALYANI ISMAIL, PhD
Department of Computer and Communication Systems Engineering,
Faculty of Engineering,
Universiti Putra Malaysia.
(Member)
MAKHFUDZAH MOKHTAR, PhD
Department of Computer and Communication Systems Engineering,
Faculty of Engineering,
Universiti Putra Malaysia.
(Member)
SAHBUDIN SHAARI, PhD
Professor
Department of Electrical, Electronic and Systems Engineering,
Faculty of Engineering,
Universiti Kebangsaan Malaysia.
(Member)
Bujang Kim Huat
Professor/ Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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This thesis submitted to the Senate of Universiti Putra Malaysia has been accepted
as fulfilment of the requirement for the degree of Master of Science. The members
of the Supervisory committee were as follows:
Ahmad Fauzi Abas, PHD
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Mohd. Adzir Mahdi, PHD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
HASANAH MOHD GHAZALI, PHD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date: 12 August 2010
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DECLARATION
I declare that the thesis is my original work except for quotations and citations
which have been duly acknowledged. I also declare that it has not been previously,
and is not concurrently, submitted for any other degree at Universiti Putra Malaysia
or at any other institutions.
SOODEH ZAHAB SANIEI
Date:
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TABLE OF CONTENTS
DEDICATION ii
ABSTRACT iiii
ABSTRAK vi
ACKNOWLEDGEMENTS viviii
DECLARATION xi
LIST OF TABLES xv
LIST OF FIGURES xvi
LIST OF ABBREVIATIONS xix
CHAPTER
1 INTRODUCTION 1
1.1 Background 1
1.2 Basic Principle of TOF 1
1.3 Problem Statement and Motivation 3
1.4 Objectives 3
1.5 Overview of This Research 4
2 LITERATURE REVIEW 6
2.1 Introduction 6
2.2 Techniques for Distance Measurements using Laser 7
2.3 Laser Range Finding Applications 10
2.4 Previous Works in Pulsed Laser Range Finders 11
2.4.1 Long Distance Measurement based Retro Reflector 12
on the Target
2.4.2 The US Army NVESD’s µLRF for Maximum 13
Range of 1500 Meter
2.4.3 Fast and High Precision Methods for 15
Short Distance Measurement
2.4.4 Gain Control Implementation with 17
Variable Attenuation
2.4.5 MARS-96 International Space Project 19
2.4.6 Light Receiver Circuit of a Laser Range Finder 22
2.4.7 High Precision Laser Range Finder with an 25
Automatic Peak Control Loop
2.5 Automatic Gain Controller 26
2.6 Summary 30
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3 METHODOLOGY 31
3.1 Introduction 31
3.2 Design Parameters 31
3.2.1 Pulse Frequency 31
3.2.2 Pulse Width 32
3.2.3 Receiver Sensitivity 33
3.2.4 Maximum Sensitivity 35
3.2.5 Measurement Resolution 35
3.3 Tools and Components 36
3.4 Receiver Design 36
3.4.1 Pulse Detector Circuit Design 36
3.4.2 Counter Design 49
3.5 Experimental Setup 53
3.6 Summary 54
4 RESULTS AND DISCUSSION 55
4.1 Simulation Results of the Designed Pulse Detector Circuit 55
4.1.1 Low pass Filter 55
4.1.2 Operational Amplifier 56
4.2 PCB Design and Construction 56
4.3 Circuit Analysis using Pattern Generator 58
4.3.1 Non-Inverting Amplifier Output 58
4.3.2 Effect of Vref on the Pulse Detector Circuit 59
4.3.3 Effect of the Noise and DC Offset on the 65
Output Signal
4.3.4 Variable Offset 68
4.3.5 Real-time Measurement for Moving Objects 71
in Military Applications
4.4 FPGA Results using Quartus Software 71
4.5 Summary 73
5 CONCLUSION AND RECOMMENDATION 74
FOR FUTURE WORK
5.1 Conclusion 74
5.2 Recommendation for Future Work 75
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REFERENCES 77
APPENDIX 79
BIODATA OF STUDENT 80
LIST OF PUBLICATIONS 81
