Ultra-Wideband Communication-Transceiver Design: UoN PRJ 092 Report

This project report details the design of an Ultra-Wideband (UWB) communication transceiver, focusing on a software radio approach for impulse-based UWB. The design aims for a raw data rate of 100 Mbps with a reconfigurable digital receiver. The transmitter utilizes a step recovery diode to generate 500 picosecond Gaussian pulses, while the receiver employs parallel ADCs and an FPGA for data processing. BPSK modulation and Digital Leading Edge Detection (DLED) are used, and the design is verified through MATLAB SIMULINK simulations, analyzing baseband processing with an AWGN channel. The project explores the advantages and challenges of UWB technology, offering a flexible platform for research and implementation of various case scenarios through software modifications.

UNIVERSITY OF NAIROBI
COLLEGE OF ARCHITECTURE AND ENGINEERING
DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERING
FIFTH YEAR PROJECT REPORT
PROJECT CODE: PRJ 092
TITLE:
ULTRA-WIDEBAND COMMUNICATION-TRANSCEIVER
DESIGN
AUTHOR:
WAFULA WANJALA GEORGE
REG. NO: F17/8255/2004
DATE OF SUBMISSION: 28-05-2009
SUPERVISOR: Dr. Vitalice Oduol
EXAMINER: Dr. M. K. Gakuru

ULTRA-WIDEBAND COMMUNICATIONS-TRANSCEIVER DESIGN
By
Wafula Wanjala George
Reg. No: F17/8255/2004
Project report submitted to the faculty of engineering
Department of Electrical & Electronic Engineering University of Nairobi
In partial fulfillment of the requirements for the degree of
Bachelor of Science
In
Electrical & Electronic Engineering
Supervisor: Dr. Vitalice Oduol
Examiner: Dr. M.K Gakuru
Date of Submission: 28 May 2009
© 2009 by Wafula Wanjala George

Acknowledgements
I take this opportunity to thank my parents Mr. Peter Wafula Ichudi and my mother
Victoria Yaola for your love, guidance, advice, instruction and financial support. I wish
to thank my mother who has been with me all the way; though you do not understand
engineering, you do understand me. Thank you.
Am indebted to Florida Simiyu, she made her room and computer available for this
project. Your proof reading, encouragement and emotional support was a much-needed
tool in the quest to fulfil these project goals and objectives. It has been much more than
an honour to be by your side and I hope to continue our relationship for many years to
come. Thank you.
I acknowledge my friends and colleagues in the Electrical Engineering department, am
convinced that you have professionally influenced this project and my life in more than
one way. Thank you.
Last but not least, my professional thanks to my project supervisor Dr. Vitalice
Oduol. Your guidance and coaching skills have made this project a reality. I highly
appreciate your commitment and availability, always addressing issues relating to this
project. Thank you. Dr. Mwema our project co-coordinator, thank you for your lectures
on report writing and creating a good environment for experimentation and verification
of this project.
Everyday am more convinced and persuaded that I would have not reached thus
far, if it were not for The Lord God Almighty. Truly, words will fail to reflect and
reciprocate what you are to me and to what extent you have affected my life. It is
amazing. In more than many ways, you have given me the strength, agility and ability to
achieve my goals. I love you God. Thank you.
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Abstract
Federal Communications Commission (FCC) of the United States of America
approval of the unlicensed frequency band between 3.1 GHz and 10.6 GHz (7500 MHz)
for indoor UWB wireless communication systems in 2002; sparked newfound
excitement about UWB communications. Ultra-Wideband Impulse Radio (UWB-IR)
with its huge advantages has been recognized as a great solution for future Wireless
Sensor Networks (WSN) and Radio Frequency Identification (RFID). UWB-IR
technique has the possibility of achieving Gbps of data rate, hundreds of meter
operation range, picoJoules energy per bit, centimetre accuracy of positioning, and low
cost implementation.
This project is focussed specifically on a software radio transceiver design for impulse-
based UWB with the ability to transmit a raw data rate of 100 Mbps yet encompasses
the adaptability of a reconfigurable digital receiver.
A 500 picoseconds wide Gaussian pulse is generated at the transmitter utilizing
the fast-switching characteristics of a step recovery diode. Critical components at the
receiver consist of a bank of ADCs performing parallel sampling and an FPGA
employed for data processing. Using a software radio design, BPSK modulation scheme
and digital receiver topology of Digital Leading Edge Detection (DLED) was used
along with a vast number of algorithms for data demodulation methods. Verification for
the design is accomplished through transmitter and receiver design simulation.
Ultimately, the transceiver design demonstrates the advantages and challenges of UWB
technology while boasting high data rate communication capability and providing the
flexibility of a research.
This project presentation in the last academic year was without simulating the
transceiver; a MATLAB SIMULINK simulation was carried out in order to analyse
baseband processing of the transceiver. Each of the corresponding transceiver blocks,
that is, the transmitter, channel and receiver simulations were performed separately. The
transceiver simulation used an AWGN channel for a 30dB signal-to-noise performance.
It is from the software approach of the transceiver that further implementation of
various case scenarios are affected by making changes in software prior to the actual
fabrication.
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Table of Contents
Acknowledgements ...................................................................................................... ii
Abstract ...................................................................................................................... iii
Table of Figures ......................................................................................................... vii
List of Abbreviations ................................................................................................ viii
Chapter 1 UWB Introduction .................................................................................... 1
1.1 What is Ultra Wideband ................................................................................... 1
1.2 Why Ultra Wideband ....................................................................................... 1
1.3 What is Transceiver ......................................................................................... 2
1.4 Project Objectives ............................................................................................ 2
1.5 Project Overview ............................................................................................. 3
Chapter 2 Issues Unique to UWB .............................................................................. 6
2.1 Introduction ..................................................................................................... 6
2.2 History ............................................................................................................ 6
2.3 Regulatory ....................................................................................................... 6
2.4 Antennas .......................................................................................................... 6
2.5 Propagation & Channel Model ......................................................................... 7
2.6 Modulations ..................................................................................................... 8
2.7 Timing acquisitions ......................................................................................... 9
2.8 Receiver Structures .......................................................................................... 9
2.9 Multiple Access ............................................................................................. 10
Chapter 3 UWB Transmitter Design Principles ...................................................... 11
3.1 Introduction ................................................................................................... 11
3.2 Impulse Analysis ........................................................................................... 11
3.2.1 Gaussian Pulse ........................................................................................ 12
3.2.2 Windowed Gaussian Pulse ...................................................................... 12
3.2.3 Calculating Power of Repetitively Sent Pulses ........................................ 13
3.3 UWB Transmitter Architecture....................................................................... 14

3.4 SRD Pulse Generators .................................................................................... 15
3.5 BPSK Modulation .......................................................................................... 17
3.6 Antennas ........................................................................................................ 17
Chapter 4 UWB Receiver Design Principles ............................................................ 19
4.1 Introduction ................................................................................................... 19
4.2 Receiver Design Architecture ....................................................................... 19
4.2.1 RF Front End ........................................................................................... 19
4.2.2 ADC/ Clock Distribution ......................................................................... 20
4.2.3 Digital Processing .................................................................................. 21
4.3 Digital Leading Edge Detection Receiver Topology ....................................... 22
4.4 Data demodulation ......................................................................................... 24
Chapter 5 UWB Transceiver Design Simulation ..................................................... 25
5.1 Introduction ................................................................................................... 25
5.2 QAM/BPSK Modulation ................................................................................ 25
5.3 UWB Transmitter ............................................................................................ 27
5.3.1 Bernoulli Binary Generator ..................................................................... 27
5.3.2 Buffer ..................................................................................................... 27
5.3.3 BPSK Modulator Baseband ..................................................................... 27
5.3.4 Discrete Time Scatter Plot Scope ............................................................ 28
5.3.5 Pad Block ............................................................................................... 28
5.3.6 IFFT Block ............................................................................................. 28
5.3.7 Unbuffer Block ....................................................................................... 29
5.3.8 Spectrum Scope ...................................................................................... 29
5.4 UWB Channel ................................................................................................ 29
5.5 UWB Receiver ............................................................................................... 30
5.5.1 FFT Block ............................................................................................... 31
5.5.2 Selector ................................................................................................... 31
5.5.3 To Frame Conversion .............................................................................. 31

5.5.4 BPSK Demodulator ................................................................................. 31
5.6 Discussion And Analysis ................................................................................ 32
Chapter 6 UWB Applications .................................................................................. 33
6.1 Introduction .................................................................................................. 33
6.2 Radar Applications ....................................................................................... 33
6.3 Communications ............................................................................................ 34
6.4 Location Aware Communications................................................................... 35
Chapter 7 Future Work and Recommendations ...................................................... 38
7.1 Conclusion and Recommendations ................................................................. 38
7.2 Future Work ................................................................................................... 38
References .................................................................................................................. 40
Appendix A Summary of FCC Regulations on UWB .............................................. 41
Appendix B Circuit Design for UWB Transceiver .................................................. 43
Appendix C Transceiver System Simulation in MATLAB ...................................... 47

Table of Figures
Figure 1.1 UWB Signal Design points .......................................................................... 1
Figure 1.2 Design Flowchart for the project ................................................................. 4
Figure 2.1 FCC Spectral mask for indoor applications .................................................. 7
Figure 2.2 UWB Modulation points ........................................................................... 8,9
Figure 3.1 Windowed Cosine Pulse ............................................................................ 13
Figure 3.2 Power available in the UWB Band and in the signal .................................. 14
Figure 3.3 UWB generic transmitter Architecture ....................................................... 14
Figure 3.4 SRD current and stored charge ............................................................. 15,16
Figure 3.5 Comparison between transmitted & Radiated Pulse ................................... 18
Figure 4.1 UWB Receiver Design ............................................................................... 19
Figure 4.2 Block diagram of Parallel Time Sampling technique .................................. 21
Figure 4.3 Threshold detection in Gaussian Noise ...................................................... 24
Figure 5.1 QAM/BPSK Modulation Model ................................................................. 26
Figure 5.2 QAM/BPSK Modulation Scope Display .................................................... 26
Figure 5.3 UWB Transmitter design block in MATLAB ............................................. 27
Figure 5.4 Transmitted Waveform In MATLAB .......................................................... 29
Figure 5.5 UWB Channel with AGWN ....................................................................... 30
Figure 5.6 UWB Receiver design block in MATLAB ................................................. 30
Figure 5.7 UWB Received Waveform in MATLAB .................................................... 32
Figure 6.1 Communication Applications ..................................................................... 35
Figure B.1 UWB Schematic of the Input .................................................................... 35
Figure B.2 UWB Schematic of the SRD Pulse Generator ............................................ 35
Figure B.3 UWB Receiver Circuit design ................................................................... 35
Figure C.1 UWB Transceiver Design in SIMULINK ................................................. 35
vii

List of Abbreviations
FCC – Federal Communications Commissions
UWB – Ultra Wideband
Mbps – Million Bits per Second
SRD – Step Recovery Diode
PSD- Power Spectral Density
Pdf - Probability density function
dB - Decibels
BPSK – Binary Phase Shift Key
RF – Radio Frequency
ADC – Analogue Digital Converter
I-UWB, IR-UWB – Impulse Ultra Wideband
GHz – Gigahertz
DC – Direct Current
DSP – Digital Signal Processing
TH-PAM – Time Hopping Pulse Amplitude Modulation
PRF – Pulse Repetition Frequency
HPA – High Pass Amplifier
BPF- Band Pass Filter
LNA – Low Noise Amplifier
SNR – Signal-to-Noise Ratio
QAM – Quadrature Amplitude Modulation
FPGA – Field Programmable Gate Array
PBER – Probability Bit Error Rate
PD – Probability Of Detection
CFAR – Constant False Alarm Rate
EIRP – Effective Isotropically Radiated Power
LPI – Low Probability of Intercept
DLED – Digital Leading Edge Detection
vii

Chapter 1 Introduction
1.1 What is Ultra-Wideband
A UWB system is defined as any radio system that has a 10-db bandwidth larger
than 20% of its center frequency or has a 10-db bandwidth equal to and larger than
500MHz. In other words, a UWB system is also defined by the FCC as any wireless
scheme that occupies a fractional bandwidth W/f c≥ 20% where W is the transmission
bandwidth and f c is the band center, or more than 500MHz of absolute bandwidth. The
formula proposed for calculating fractional bandwidth is 2(f H - fL)/ (f H + fL) where f H
represents the upper frequency of the 10-db emission limit and f L represents the lower
frequency limit of the 10-db emission limit. The approval of UWB technology made by
the FCC of the United States in 2002 reserves the unlimited frequency band between
3.1GHz and 10.6GHz for indoor UWB wireless communication system.
Figure 1.1 UWB signal design points [1].
1.2 Why Ultra wideband
UWB has clearly shown various advantages in both indoor and industrial applications,
which encourage its use as a promising solution for high data rate short-range and
moderate range wireless communications and ranging. Its centimeter accuracy in
ranging and communications provide unique solutions to applications including
logistics, security applications, medical applications, control of home appliances, search
and rescue, family communications, supervision of children and military applications.
UWB has several features that differentiate it from conventional narrowband systems.
This includes:
i) Large instantaneous bandwidth enables fine time resolution for network time
distribution, precision location capability, or use as radar.
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ii) Short duration pulses are able to provide robust performance in dense multipath
environments by exploiting paths that are more resolvable. This allows better
immunity to multi-path propagation.
iii) Low power spectral density allows co-existence with existing users and has a
low probability of intercept (LPI). This permits low interference.
iv) Data may be traded for power spectral density and multipath performance.
v) Availability of low cost transceivers, low transmit power.
Taken together these features give UWB systems a clear technical advantage over the
more conventional approaches in high multipath environments at low to medium data
rates. These arguments prove why UWB is the preferred choice in high multipath
environments at low to medium data rates.
1.3 What is a UWB Transceiver
A transceiver is a device that has both a transmitter and receiver, which are combined to
share common circuitry or a single housing, e.g. a walkie-talkie. Hence, a UWB
transceiver incorporates both the UWB transmitter and receiver in a single housing.
Trends in UWB transceiver design methods have been proposed to overcome various
unresolved issues in low complexity channel acquisitions transceiver design. The
methods have been classified into two primary categories:-Digital and mixed
analog/digital (solutions) schemes.
1.4 Project Objectives
The main aim of this project is:
• To study Ultra-Wideband Communications System
• To design a transceiver system based UWB
• To demonstrate that the UWB transceiver works
With the objectives in hand, the corresponding experiments, investigations, discussions
and solutions were performed to design UWB systems. UWB has proven to be a
stimulating, exciting, rejuvenating and brain storming communication system that is
wide in scope in terms of knowledge and experimentation. It has been proven that in
order to design any transceiver system based on UWB several factors have to be
evaluated, namely [1]:
i) What is permissible under the rules & regulations?
ii) What level of co-existence with other services in the frequency band is desirable
iii) What technological constraints there are from the feasibility, cost and
marketability points of view?
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These and many other factors formed the foundational basis for the questions that
needed to be answered for any UWB transceiver, design to be viable. The regulations
define the broad rules & conditions for UWB communications systems to access &
share a 7.5GHz swath of spectrum extending from 3.1GHz to 10.6GHz. To gain market
acceptance, UWB radios will need to be cheaper, flexible and to co-exist with, share
and even perhaps interoperate with other radio services.
Furthermore, UWB technology will need to be physically implemented in cost-effective
integrated circuits. With adequate knowledge and foresight in hand, an impulse-UWB
communication system was design based on software-defined radio. A UWB transceiver
system had the following specifications:
• Data rate of 100 Mbps
• Transmitter design:
• Modulation Schemes: BPSK
• Receiver Design: Digital Leading Edge Detection
Simulation in MATLAB version 7.6.0.324 (R2008a) was to essentially show and proof
that these design objectives were tested, experimented and proved. The system
simulation was necessary to uncover any design flaws and calculate system performance
statistics based on the final system design. Finally, the optimistic results from these
simulations help support the overall goal of producing a UWB transceiver capable of
high data rate.
1.5 Project Overview
This project report is organised in such a way that each design objectives has been
experimented, investigated, researched, discussed and interpreted with relevant
conclusions and summaries being finalised. It is through these incentives and
innovations that the project has been classified into seven major topics namely
introduction to UWB, transmitter design, receiver design, system simulation,
applications and future work. Similarly, each topic has two sections, the introduction,
and main text. A flowchart maps the direction to realizing these project goals and
objectives as shown on figure 1.2.
3