SEMINAR REPORT on Ultra Wide Band(UWB)

A SEMINAR REPORT ON

RF transmission based on Microwave UWB

Submitted in partial fulfilment of the requirements for the

award of the degree of

BACHELOR OF TECHNOLOGY

In

ELECTRONICS AND COMMUNICATION

ENGINEERING

Submitted by

VINOD V: 07402144

DEPARTMENT OF ELECTRONICS AND COMMUNICATION

ENGINEERING

SREE CHITRA THIRUNAL COLLEGE OF ENGINEERING

THIRUVANANTHAPURAM 695 018

NOVEMBER 2010

SREE CHITRA THIRUNAL COLLEGE OF ENGINEERING,

THIRUVANANTHAPURAM - 695 018.

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING.

CERTIFICATE

Certified that seminar work entitled “RF transmission based on Microwave UWB”

is a bonafide work carried out in the seventh semester by “VINOD V (07402144)” in

partial fulfilment for the award of Bachelor of Technology in “ELECTRONICS

AND COMMUNICATION ENGINEERING” from University of Kerala during the

academic year 2010-2011, who carried out the seminar work under the guidance and

no part of this work has been submitted or published any where earlier for the award

of any degree.

SEMINAR CO-ORDINATOR HEAD OF THE DEPARTMENT

SUBHA V S.VAIDYANATHAN Lecturer, Professor, Department of ECE Department of ECE SCT College of Engineering SCT College of Engineering Thiruvananthapuram-18 Thiruvananthapuram-18

ACKNOWLEDGEMENT

I owe a great many thanks to a great many people who helped and supported

us during the making of this seminar. My deepest thanks to Ms Subha.V, lecturer in

Electronics and Communication Engineering, Sree Chitra Thirunal College of

Engineering, Trivandrum, the seminar co-ordinator for guiding and correcting various

documents with attention and care. They have taken pain to go through the seminar

and make necessary corrections as and when needed.

I gratefully obliged to thank Prof. S.Balachandran, Principal, Sree Chitra

Thirunal College of Engineering, Trivandrum and Prof. S.Vaidyanathan, Head of

the Department, Department of Electronics & Communication Engineering for their

timely assistance during the course of this seminar.

I would like to thank our institution and our faculty members without whom

this seminar would have been a distant reality. I also extend our heartfelt thanks to our

families and well wishers. Last but not the least I would like to express our gratitude

to God almighty.

Vinod V

ABSTRACT

Ultra-wideband (UWB) transmission has recently received great attention in

both academia and industry for applications in wireless communications. It was

among the CNN’s top 10 technologies to watch in 2004. 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 or larger than 500 MHz, The recent

approval of UWB technology by Federal Communications Commission (FCC) of the

United States reserves the unlicensed frequency band between 3.1 and 10.6 GHz (7.5

GHz) for indoor UWB wireless communication systems. It is expected that many

conventional principles and approaches used for short-range wireless communications

will be reevaluated and a new industrial sector in short-range (e.g., 10 m) wireless

communications with high data rate (e.g., 400 Mbps) will be formed. Further,

industrial standards IEEE 802.15.3a (high data rate) and IEEE 802.15.4a (very low

data rate) based on UWB technology have been introduced.

The design and implementation rules are outlined and described in

http://www.wimedia.org/ & http://www.uwbforum.org/

TABLE OF CONTENTS

LIST OF FIGURES i

LIST OF TABLES ii

CHAPTER TITLE PAGE NO:

1.0 INTRODUCTION 1

1.1. History and Background 2

1.2. FCC Emission limits 3

1.3. UWB Concepts 4

1.4. UWB Signals 5

2.0 WHY UWB 7

3.0 BAND-PASS UWB 11

3.1 Filter Technologies 11

4.0 MULTIBAND-OFDM APPROACH 14

5.0 IR-UWB vs. MB-OFDM 19

6.0 LNA ARCHITECTURE 20

7.0 UWB ANTENNAS 22

8.0 UWB VS. SPREAD SPECTRUM 24

9.0 UWB APPLICATIONS 25

9.1 UWB Radar 27

9.1.1 Measuring method 28

9.1.2 UWB radar over NB radar 29

9.1.3 Position Estimation Techniques 30

10. CHALLENGES TO UWB 33

11. CONCLUSION 34

REFERENCES 35

APPENDIX 36

i

LIST OF FIGURES

FIGURE NAME PAGE NO:

FIG. 1.1 UWB History 2

FIG. 1.2 FCC Emission limits 3

FIG. 1.3 UWB and Narrowband 4

FIG. 1.4(a) UWB Wavelet 5

FIG. 1.4(b) Wavelet generation 6

FIG.2.1 Coexistence with NB 7

FIG. 3 Band-pass UWB 11

FIG. 3.1(a) UWB Filter response 12

FIG. 3.1 (b) Micro-strip filter 13

FIG. 3.1 (c) UWB Notch filter 13

FIG. 4 (a) DS-UWB 3.1 to 5 GHz 15

FIG. 4 (b) DS-UWB 6 to 10.6 GHz 15

FIG. 4 (c) MB-OFDM 16

FIG. 4 (d) MB-OFDM Generation 17

FIG. 4(e) MB-OFDM with CR 18

FIG. 6(a) LNA Architecture 20

FIG. 6 (b) Impedance matching 20

FIG. 6 (c) Interference suppression 21

ii

FIG. 7 UWB Antennas 23

FIG. 8 UWB vs. Spread Spectrum 24

FIG. 9 OPPN 26

FIG. 9.1 SRR 27

FIG. 9.1.3 (a) UWB position estimation 30

FIG. 9.1.3 (b) UWB position estimation- Setup 31

LIST OF TABLES

TABLE NAME PAGE NO:

TABLE.1.3 UWB, WB & NB 4

TABLE.4 MB-OFDM Generator 17

TABLE.5 MB-OFDM vs. DS-UWB 19

TABLE.7 Antenna design 23

TABLE.10 UWB Interference 33

1

1. INTRODUCTION

Every radio technology allocates a specific part of the spectrum; for example,

the signals for TVs, radios, cell phones, and so on are sent on different frequencies to

avoid interference to each other. As a result, the constraints on the availability of the

RF spectrum become more and stricter with the introduction of new radio services.

Ultra-wideband (UWB) technology offers a promising solution to the RF spectrum

drought by allowing new services to coexist with current radio systems with minimal

or no interference. This coexistence brings the advantage of avoiding the expensive

spectrum licensing fees that providers of all other radio services must pay.

This seminar provides a comprehensive overview of ultra-wideband

Communications.

2

1.1 History and Background

Ultra-wideband communications is not a new technology; in fact, it was first

employed by Guglielmo Marconi in 1901 to transmit Morse code sequences across

the Atlantic Ocean using the spark gap radio transmitters. However, the benefit of a

large bandwidth and the capability of implementing multiuser systems provided by

electromagnetic pulses were never considered at that time. Approximately fifty years

after Marconi, modern pulse-based transmission gained momentum in military

applications in the form of impulse radars. Some of the pioneers of modern UWB

communications in the United States from the late 1960s are Henning Harmuth of

Catholic University of America and Gerald Ross and K. W. Robins of Sperry Rand

Corporation.

From the 1960s to the 1990s, this technology was restricted to military and

Department of Defense (DoD) applications under classified programs such as highly

secure communications. However, the recent advancement in micro processing and

fast switching in semiconductor technology has made UWB ready for commercial

applications. Therefore, it is more appropriate to consider UWB as a new name for a

long-existing technology. As interest in the commercialization of UWB has increased

over the past several years, developers of UWB systems began pressuring the FCC to

approve UWB for commercial use. In February 2002, the FCC approved the First

Report and Order (R&O) for commercial use of UWB technology under strict power

emission limits for various devices.

FIG. 1.1 UWB History

3

1.2 Fcc Emission Limits

In order to protect existing radio services from UWB interference, the FCC

has assigned conservative emission masks between 3.1 GHz and 10.6 GHz for

commercial UWB devices. The maximum allowed power spectral density for these

devices—that is,–41.3 dBm/MHz, or 75 nW/MHz—places them at the same level as

un-intentional radiators (FCC Part 15 class) such as televisions and computer

monitors. The spectral mask for outdoor devices is 10 dB lower than that for indoor

devices, between 1.61 GHz and 3.1 GHz, as shown in above Figure 1.2. According to

FCC regulations, indoor UWB devices must consist of handheld equipment, and their

activities should be restricted to peer-to-peer operations inside buildings.

The FCC’s rule dictates that no fixed infrastructure can be used for UWB

communications in outdoor environments. Therefore, outdoor UWB communications

are restricted to handheld devices that can send information only to their associated

receivers.

FIG. 1.2- UWB FCC Emission

4

1.3 Uwb Concepts

Traditional narrowband communications systems modulate continuous

waveform (CW) RF signals with a specific carrier frequency to transmit and receive

information. A continuous waveform has well-defined signal energy in a narrow

frequency band that makes it very vulnerable to detection and interception. Above

Figure 1.3 represents both narrowband & wideband signals in the time and frequency

domains. UWB systems use carrier-less, short-duration (picoseconds to nanosecond)

pulses with a very low duty cycle (less than 0.5 percent) for transmission and

reception of the information.

FIG. 1.3- UWB & Narrowband

TABLE.1.3 – UWB, Wide band, & Narrow

5

Low duty cycle offers a very low average transmission power in UWB

communications systems. The average transmission power of a UWB system is on the

order of microwatts, which is a thousand times less than the transmission power of a

cell phone! However, the peak or instantaneous power of individual UWB pulses can

be relatively large, but because they are transmitted for only a very short time, the

average power becomes considerably lower. Consequently, UWB devices require low

transmit power due to this control over the duty cycle, which directly translates to

longer battery life for handheld equipment. Since frequency is inversely related to

time, the short-duration UWB pulses spread their energy across a wide range of

frequencies—from near DC several gigahertz (GHz)—with very low power spectral

density (PSD). The wide instantaneous bandwidth results from the time-scaling

property of theoretical Fourier transforms.

1.4 Uwb Signals

UWB modulates an impulse-like waveform (WAVELET) with Data. A typical

baseband UWB pulse, also called mono-pulse, such as the Gaussian first derivative

pulse can be used. UWB signals must have bandwidths of greater than 500MHz or a

fractional bandwidth larger than 20 percent at all times of transmission. Fractional

(relative) bandwidth is a factor used to classify signals as narrowband, wideband, or

ultra-wideband and is defined by the ratio of bandwidth at –10 dB points to center

frequency.

FIG. 1.4(a) - UWB Wavelet

6

where fh and f1 are the highest and lowest cutoff frequencies (at the –10 dB

point) of a UWB pulse spectrum, respectively. A UWB signal can be any one of a

variety of wideband signals, such as Gaussian, chirp, wavelet, or Hermite-based short-

duration pulses. Above Figure 1.4(a) represents a Gaussian monocycle as an example

of a UWB pulse.

Wavelet Generation

The development of laser-actuated semiconductor fast-acting switches that

can produce impulses or short duration waveforms of one or several cycles has

been of interest for UWB. The traveling wave tube (TWT) can be used. It can be

excited with a narrow impulse, but its energy is limited by the peak power of

the TWT.

FIG. 1.4(b) - Wavelet Generation

7

2. WHY UWB?

The nature of the short-duration pulses used in UWB technology offers several

advantages over narrowband communications systems. Next, we discuss some of the

key benefits that UWB brings to wireless communications.

2.1 Ability to Share the Frequency Spectrum

UWB systems reside below the noise floor of a typical narrow-band receiver

and enables UWB signals to coexist with current radio services with minimal or no

interference as illustrated in FIG. 2.1.

2.2 Large Channel Capacity

One of the major advantages of the large bandwidth for UWB pulses is

improved channel capacity. Channel capacity, or data rate, is defined as the maximum

amount of data that can be transmitted per second over a communications channel.

FIG. 2.1-Coexistence with Narrow band

8

The large channel capacity of UWB communications systems is evident from

Hartley-Shannon’s capacity formula. Where C represents the maximum channel

capacity, B is the bandwidth, and SNR is the signal-to-noise power ratio. As shown in

Equation, channel capacity C linearly increases with bandwidth B. Therefore, having

several gigahertz of bandwidth available for UWB signals, a data rate of gigabits per

second (Gbps) can be expected.

However, due to the FCC’s current power limitation on UWB transmissions,

such a high data rate is available only for short ranges, up to 10 meters. This makes

UWB systems perfect candidates for short-range, high-data-rate wireless applications

such as wireless personal area networks (WPANs). The trade-off between the range

and the data rate makes UWB technology ideal for a wide array of applications in

military, civil, and commercial sectors.

2.3 Ability to Work with Low Signal-To-Noise Ratios

The Hartley-Shannon formula for maximum capacity also indicates that the

channel capacity is only logarithmically dependent on signal-to-noise ratio

(SNR).Therefore, UWB communications systems are capable of working in harsh

communication channels with low SNRs and still offer a large channel capacity as a

result of their large bandwidth.

2.4 Low probability of intercept and detection

Because of their low average transmission power, UWB communications

systems have an inherent immunity to detection and intercept. With such low

transmission power, the eaves-dropper has to be very close to the transmitter (about 1

meter) to be able to detect the transmitted information. In addition, UWB pulses are

time modulated with codes unique to each transmitter/receiver pair. The time

modulation of extremely narrow pulses adds more security to UWB transmission,

because detecting picoseconds pulses without knowing when they will arrive is next

to impossible. Therefore, UWB systems hold significant promise of achieving highly

9

secure, low probability of intercept and detection (LPI/D) communications that is a

critical need for military operations.

2.5 Resistance to Jamming

Processing gain (PG) is a measure of a radio system’s resistance to jamming

and is defined as the ratio of the RF bandwidth to the information bandwidth of a

signal. The frequency diversity caused by high processing gain makes UWB signals

relatively resistant to intentional and unintentional jamming, because no jammer can

jam every frequency in the UWB spectrum at once. Therefore, if some of the

frequencies are jammed, there is still a large range of frequencies that remains

untouched. However, this resistance to jamming is only in comparison to narrowband

and wideband systems. Hence, the performance of a UWB communications system

can still be degraded, depending on its modulation scheme, by strong narrow-band

interference from traditional radio transmitters coexisting in the UWB receiver’s

frequency band.

2.6 High performance in multipath channels

The phenomenon known as multipath is unavoidable in wireless

communications channels. It is caused by multiple reflections of the transmitted signal

from various surfaces such as buildings, trees, and people. The straight line between a

transmitter and a receiver is the line of sight (LOS); the reflected signals from

surfaces are non-line of sight (NLOS).

The effect of multipath is rather severe for narrowband signals; it can cause

signal degradation up to –40 dB due to the out-of-phase addition of LOS and NLOS

continuous waveforms. On the other hand, the very short duration of UWB pulses

makes them less sensitive to the multipath effect. Because the transmission duration

of a UWB pulse is shorter than a nanosecond in most cases, the reflected pulse has an

extremely short window of opportunity to collide with the LOS pulse and cause signal

degradation.

10

2.7 Superior penetration properties

Unlike narrowband technology, UWB systems can penetrate effectively

through different materials. The low frequencies included in the broad range of the

UWB frequency spectrum have long wavelengths, which allows UWB signals to

penetrate a variety of materials, including walls. This property makes UWB

technology viable for through-the-wall communications and ground-penetrating

radars (GPRs). However, the material penetration capability of UWB signals is useful

only when they are allowed to occupy the low-frequency portion of the radio

spectrum.

2.8 Simple transceiver architecture

UWB transmission is carrier-less, meaning that data is not modulated on a

Continuous waveform with a specific carrier frequency, as in narrowband and

wideband technologies. Carrier-less transmission requires fewer RF components than

carrier-based transmission. For this reason UWB transceiver architecture is

significantly simpler and thus cheaper to build.

The transmission of low-powered pulses eliminates the need for a power

amplifier (PA) in UWB transmitters. Also, because UWB transmission is carrier-less,

there is no need for mixers and local oscillators to translate the carrier frequency to

the required frequency band; consequently there is no need for a carrier recovery

stage at the receiver end. In general, the analog front end of a UWB transceiver is

noticeably less complicated than that of a narrowband transceiver. This simplicity

makes an all- CMOS implementation of UWB transceivers possible, which translates

to smaller form factors and lower production costs.

11

3. BAND-PASS UWB

Low energy, short duration UWB pulses modulates Input data. Microwave

Spectrum controlled by impulse response of BPF in FIG. 3. Modulation scheme may

be among PPM, OOK, or BPSK.

3.1 Filter Technologies

UWB band-pass filter is a key component of UWB system. It must have an

ultra wide pass-band, but also needs high selectivity to reject signals from existing

systems such as 1.6 GHz global positioning systems (GPS) and 2.4 GHz Bluetooth

systems. In addition, in some cases, the UWB band pass filter needs to introduce

steeply notched frequency bands (FIG 3.1(a)) in order to reduce interference from

existing NB radio systems located within the UWB pass-band. These requirements

increase the challenges for the UWB filter designer.

FIG. 3-Band-pass UWB

12

However, since conventional filter theory is based on the narrowband

assumption and cannot be used to design UWB band pass filters, novel techniques and

technologies need to be developed for UWB band pass filter design.

FIG. 3.1(a)-UWB Filter response

13

Micro-strip Filter

Micro strip filters only become practical above 300MHz. It is a size issue. The

inductance and capacitance of the micro strip line PCB traces to form the filter, rather

than discrete inductors and capacitors.

FIG. 3.1(b)-Micro-strip Filter

FIG. 3.1(c)-UWB Notch Filter

14

4. MULTIBAND-OFDM APPROACH

The ability of UWB technology to provide very high data rates for short

ranges (less than 10 meters) has made it an excellent candidate for the physical layer

of the IEEE 802.15.3a standard for wireless personal area networks (WPANs).

However, two opposing groups of UWB developers are battling over the IEEE

standard. The two competing technologies are single band and multiband. The

single-band technique, backed by Motorola/XtremeSpectrum, supports the idea of

impulse radio that is the original approach to UWB by using narrow pulses that

occupy a large portion of the spectrum. The multiband approach divides the available

UWB frequency spectrum (3.1 GHz to 10.6 GHz) into multiple smaller and non

overlapping bands with bandwidths greater than 500 MHz to obey the FCC’s

definition of UWB signals. The multiband approach is supported by several

companies, including Staccato Communications, Intel, Texas Instruments, General

Atomics, and Time Domain Corporation.

To date, several proposals from both groups have been submitted to the IEEE

802.15.3a working group, and the decision is yet to be made because both

technologies are impressive and have technical credibility.

The following subsections discuss the two leading candidates for the

802.15.3a standard: direct-sequence UWB (DS-UWB) and multiband orthogonal

Frequency division multiplexing (OFDM)

15

Direct-Sequence Uwb

Above figure 4(a) shows DS-UWB with 3.1-to 5-GHz range band plan. And

the below figure 4(b) shows DS-UWB with 6-to 10.6-GHz band plan

Direct-sequence UWB is a single-band approach that uses narrow UWB

pulses and time-domain signal processing combined with well-understood DSSS

techniques to transmit and receive information. Data representation in this approach is

based on simple bi-phase shift keying (BPSK) modulation, and rake receivers are

used to capture the signal energy from multiple paths in a multipath channel.

According to the proposals sent to the IEEE 802.15.3a standardization

committee by the proponents of this technology, the DS-UWB technique is scalable

and can achieve data rates in excess of 1 Gbps. The technical reason behind using DS-

FIG. 4(a)-DS-UWB 3.1 to 5 GHz

FIG. 4(b) - DS-UWB 6 to 10.6

16

UWB is the propagation benefits of ultra-wideband pulses, which experience no

Rayleigh fading. In contrast, narrowband transmissions degrade significantly due to

fading.

Multiband OFDM

The multiband UWB approach uses the 7500 MHz of the RF spectrum

available to UWB communications in a way that differs from traditional UWB

techniques. The UWB frequency band is divided into multiple smaller bands with

bandwidths greater than 500 MHz (FIG. 4(c)). This approach is similar to the

narrowband frequency-hopping technique. Dividing the UWB spectrum into multiple

frequency bands offers the advantage of avoiding transmission over certain bands,

such as 802.11a at 5 GHz, to prevent potential interference. In the multiband

approach, UWB pulses are not as narrow as in traditional UWB techniques; therefore,

synchronization requirements are more relaxed.

A variety of modulation techniques have been proposed by industry leaders

for the multiband approach; however, OFDM, which was initially proposed by Texas

Instruments, offers improved performance for high-data rate applications. In fact, both

technologies are technically valid and impressive.

Supporters of DS-UWB criticize the multiband OFDM systems for their

complexity, which results from using complex Fast Fourier Transforms (FFTs). On

the other side, advocates of multiband OFDM believe that their technique offers better

coexistence with other radio services, and they disapprove of DS-UWB because of

possible interference concerns.

FIG. 4(c)-MB-OFDM

17

The debate will likely continue until the IEEE 802.15.3a standardization

committee reaches a decision.

Mb-OFDM Generation Method

PLL provides center frequencies for first three Groups “A” bands.

FIG. 4(d)-MB-OFDM generation

TABLE.4-MB-OFDM Generator

18

Integration of Multiband and Cognitive Radio (CR)

Cognitive Radio (CR) is an emerging approach for a more flexible usage of

the precious radio spectrum resources. By investigations on the radio spectrum usage,

it has been observed that some frequency bands are largely unoccupied most of the

time, some other frequency bands are only partially occupied, and the remaining

frequency bands are heavily used.

A CR terminal can sense its environment and location and then adapt some of

its features allowing to dynamically reusing valuable spectrum. This could lead to a

multidimensional reuse (dynamical usage) of spectrum in space, frequency and time,

exceeding the severe limitations in the spectrum and bandwidth allocations (FIG.

4(e)).

FIG. 4(e)-MB-OFDM with CR

19

5. IR-UWB VS. MB-OFDM

TABLE.5-MB-OFDM vs. IR-UWB

20

6. LNA ARCHITECTURE

Due to the wide bandwidth, classical narrow band LNA design techniques

cannot be used. Feedback amplifier architecture, described in Figure 6(a), has been

considered as a good candidate for wideband amplification due to its relative

simplicity to provide flat gain and good 50 Ohms matching with respect to low noise.

Wideband Input Impedance Matching

The main challenge in UWB designs is to extend matching to the wide

frequency range of 3.1-10.6 GHz. The LNA has to exhibit good input impedance as in

FIG. 6(b).

FIG. 6(a)-LNA (Low Noise Amplifier)

FIG. 6(b)-Impedance matching

21

NB interference suppression

A tunable center frequency RF “roofing filter” applied to the UWB NB

interference mitigation problem as in FIG. 6(c). This filter will introduce significant

group delay distortion in the pass band, and so spectral shaping of the transmitted

waveform out of the interference band will also be required to minimize the resulting

degradation in system performance.

In the second case, an accurate estimation of the frequency, phase, and

amplitude of the jammer is required to significantly reduce the interference level.

FIG. 6(c)-NB Interference

22

7. UWB ANTENNAS

Antennas are particularly challenging aspect of UWB. If an impulse is fed to

an antenna, it tends to ring, severely distorting the pulse and spreading it out in time.

Also have poor matching and large reflections. Conventional wideband antennas such

as the log-periodic and the spiral are wideband in amplitude, but not in phase;

they distort the UWB signal.

The best antennas for UWB are arrays of TEM horns. The higher the

frequency the antennas can be equally small (FIG. 7). In UWB systems, antenna

design is one of key technologies and has been widely investigated by both academia

and industry. The antenna design considerations are strongly dependent on the

modulation scheme, which the UWB systems are using, and applications.

In general, MB-OFDM UWB wireless communication systems require the

antennas which should have broadband response in terms of return loss, gain at the

directions of interest, and /or polarization. Such requirements are almost the same as

the designs for conventional broadband wireless systems but a required extremely

broad bandwidth of 50% to 100% with a consistent gain response. However,

additional attention must be paid for pulse-based UWB systems where the UWB

antenna usually function as a band pass filter and tailor the spectra of the

radiated/received pulses so that the waveforms of radiated/received pulses are

distorted.

23

TABLE.7-UWB Antenna design

FIG. 7-Antenna shapes

24

8. Uwb Vs Spread Spectrum

Although UWB and spread-spectrum (SS) techniques share the same

advantage of expanded bandwidth as evident from FIG. 8, the method of achieving

the large bandwidth is the main distinction between the two technologies. In

conventional spread-spectrum techniques, the signals are continuous-wave sinusoids

that are modulated with a fixed carrier frequency.

In UWB communications, on the other hand, there is no carrier frequency; the

short duration of UWB pulses directly generates an extremely wide bandwidth.

Another distinguishing factor in UWB is the very large bandwidth. Spread-spectrum

techniques can offer megahertz of bandwidth, while UWB pulses provide several

gigahertz of bandwidth. Above figure 8 shows the time and frequency domain

representation of narrowband, wideband, and UWB signals.

The low transmission power could be a disadvantage for UWB systems,

because the information can travel only short distances. Therefore, for long-range

applications, spread-spectrum techniques are still more appropriate.

FIG. 8-UWB & SS

25

9. UWB APPLICATIONS

The trade-off between data rate and range in UWB systems holds great

promise for a wide variety of applications in military, civilian, and commercial

sectors. The FCC categorizes UWB applications as radar, imaging, or

communications devices. Radar is considered one of the most powerful applications

of UWB technology. The fine positioning characteristics of narrow UWB pulses

enables them to offer high-resolution radar (within centimeters) for military and

civilian applications. Also, because of the very wide frequency spectrum band, UWB

signals can easily penetrate various obstacles. This property makes UWB-based

ground-penetrating radar (GPR) a useful asset for rescue and disaster recovery teams

for detecting survivors buried under rubble in disaster situations.

In the commercial sector, such radar systems can be used on construction sites

to locate pipes, studs, and electrical wiring. The same technology under different

regulations can be used for various types of medical imaging, such as remote heart

monitoring systems. In addition, UWB radar is used in the automotive industry for

collision avoidance systems. Moreover, the low transmission power of UWB pulses

makes them ideal candidates for covert military communications.

UWB pulses are extremely difficult to detect or intercept; therefore,

unauthorized parties will not get access to secure military information. Also, because

UWB devices have simpler transceiver circuitry than narrowband transceivers, they

can be manufactured in small sizes at a lower price than narrowband systems.

Small and inexpensive UWB transceivers are excellent candidates for wireless

sensor network applications for both military and civilian use. Such sensor networks

are used to detect a physical phenomenon in an inaccessible area and transfer the

information to a destination. A military application could be the detection of

biological agents or enemy tracking on the battlefield. Civilian applications might

include habitat monitoring, environment observation, health monitoring, and home

automation.

26

The precise location-finding ability of UWB systems can be used in inventory

control and asset management applications, such as tagging and identification

systems—for example, RFID tags. Also, the good performance of UWB devices in

multipath channels can provide accurate geo-location capability for indoor and

obscured environments where GPS receivers won’t work.

The high-data-rate capability of UWB systems for short distances has

numerous applications for home networking and multimedia-rich communications in

the form of WPAN applications. UWB systems could replace cables connecting

camcorders and VCRs, as well as other consumer electronics applications, such as

laptops, DVDs, digital cameras, and portable HDTV monitors. No other available

wireless technologies—such as Bluetooth or 802.11a/b—are capable of transferring

streaming video.

UWB Outdoor Peer-To-Peer Network (OPPN)

Downloading of video movie purchase or rental, for example, is a very data-

intensive activity that could be enabled by UWB.

FIG. 9-UWB OPPN

27

9.1 Uwb Radar (Short-Range Radar (SRR))

The wide bandwidth of UWB signals implies a fine time resolution that gives

them a potential for high-resolution positioning applications /Localization and

tracking (LT)/ranging, provided that the multipath are dealt with. As of Short Pulse

Width we can Resolve Multipath Components. Above Figure 9.1 demonstrates

external views of this UWB radar model.

The major specifications of the prototype are given be

• Operation range 8 m;

• Pulse power 10 mW;

• Average power 80 ~W;

• Width of the antenna’s pattern: 8° x 8°; and

• Duration of radiated radio pulses 2 ns.

FIG. 9.1-UWB SRR

28

9.1.1 The Measuring Method of Uwb Radar

While constructing UWB radars, as with constructing conventional narrow-

band radars, we use the property of electromagnetic waves to be scattered from a

boundary of two media with different parameters. The short electromagnetic pulses

radiated by radar are scattered by a moving object. The oscillation frequency within

the pulse and the repetition frequency of pulses are changed owing to the Doppler

Effect. The sign of these variations depends on the direction of target movement

relative to the radar and the variation value depends on the object's radial velocity.

According to this direction, the signal spectrum is going wider or narrower and moves

toward high or low frequency areas.

The radars work in conditions of high level of passive noise - the signals,

reflected from walls and stationary objects, which will have large amplitude and will

disguise useful signals. Time slots, opening the receiver at the moment of input of

signal reflected from object at distance defined are formed in receiving path to

eliminate interfering pulses. This task in radar design is executed by a time

discriminator, being gated. It consists of fast-acting electronic switches. The

switching time is on the order of 200-300 picoseconds. The switches connect the

receiving antenna to the UWB amplifier at the moment of signal input. These

moments are defined by a delay magnitude of the control signal at a software-

controlled delay line. All of the rest of the time, the receiver is closed. The signals

received at time slots are detected and amplified in integrating amplifier and the

signal, carrying data of target motion is selected at its output.

The time constant of integration of integrating amplifier is chosen

Independently of the bandwidth of the desired signal. For example, measuring a

person's vital signs, the bandwidth of the desired signal is near 40 - 50 Hz, that

corresponds to an accumulation of 10 - 30 thousands of pulses, approximately. The

accumulation permits us to decrease the average radiated power of the transmitter and

increase the signal-to-noise ratio at the input of the amplifier.

29

The selected and amplified low-frequency signal enters the analog-digital

converter (ADC). The microprocessor-controlled unit directs the work of the radar on

given algorithms, monitors the state of major units and modules, and provides data

output for further digital processing in the computer. The selection of moving targets,

fast Fourier transform, and digital filtration are software-programmable at the

computer.

9.1.2 UWB Radar over NB Radar

• Higher range resolution and accuracy .Ultra High Range Resolution

(UHRR)

• enhanced target recognition

• immunity to passive “interference”

• immunity to co-located radar transmissions

• signals scattered by separate target elements do not interfere

• operational security because of the extremely large spectral spreading

• ability to detect very slowly moving or stationary targets

• Multiple targets can be resolved

• With a long pulse NB radar waveform, changes in the target aspect

cause a change only in the amplitude of the echo signal. With UWB

signals, the echo signal will change, which makes efficient signal processing.

• NB signal processing in radar almost always utilizes the envelope. With

UWB waveforms, either the envelope or the RF signal can be used.

• In indoor and dense urban environments the GPS signal is typically

unavailable.

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9.1.3 Position Estimation Techniques

In the below set-up FIG. 9.1.3(b) Short-pulse RF emissions from the tags are

subsequently received by either all, or a subset, of these sensors and processed by the

central hub CPU.

FIG. 9.1.3(a) - Target in piconet

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A set of three or more receivers (four receivers are typically used) are

positioned at known coordinates within, or about the periphery of, the area to be

monitored as in FIG 9.1.3(a).

In order to comprehend the high-precision positioning capability of UWB

signals, position estimation techniques should be investigated first. Position

estimation of a node in a wireless network involves signal exchanges between that

node (Called the target_ node; i.e., the node to be located) and a number of reference

nodes (FIG. 9.1.3(b)). A central unit that gathers position information from the

reference nodes and then estimates the position based on those signal parameters.

Signal parameters, such as TOA (time-of-arrival), angle-of-arrival (AOA), TDOA

(Time Difference of Arrival), RTD (Round Trip Delay) and/or received signal

FIG. 9.1.3(b)-UWB position estimation

32

strength (RSS) are estimated. Short-pulse RF emissions from the tags are

subsequently received by receivers and processed by the central hub CPU. A typical

tag emission consists of a short burst, which includes synchronization preamble, tag

identification (ID), optional data field (e.g., tag battery indicator), and FEC bits. Time

differences of arrival (TDOA) of the tag burst at the various receiver sites are

measured and sent back to the central processing hub for processing. Calibration is

performed at system startup by monitoring data from a reference tag, which has been

placed at a known location.

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10. CHALLENGES TO UWB

► suspicious about the NB interference as shown in TABLE.10

► extreme antenna bandwidth requirements

► very accurate timing synchronization need for correlation -based receiver

► Complex RAKE-type receiver to cope with significant amount of energy in

the multipath

► filter matching accuracy

► timely approval from the regulatory bodies

► lack of an universal standard

TABLE.10-Systems degraded by UWB

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11. CONCLUSION

With the recent advances in semiconductor device technology and the FCC’s

approval of the unlicensed use of ultra-wideband systems, UWB development has

moved from research labs and classified military projects to the commercial sector.

UWB technology brings many opportunities as well as challenges to the world of

wireless communications. UWB is a promising technology for the Next Generation

Wireless Systems!

Home audio systems and PCs without the confusing and messy cables, and

even more tech savvy cell phones are the promise of UWB. Some people question

whether UWB really will impact consumer life. A better question is when? There is

a definite demand for the applications that can be developed using UWB. UWB also

has a unique edge over competing technologies in its low cost and low power model.

Unfortunately early regulatory division has split UWB implementers down the

middle. Countries around the world have been reluctant to release radio spectrum for

UWB use. The consequential lack of a universal standard must be addressed so

consumers can reap the benefits of UWB.

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REFERENCES

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2. Hao, ‘UWB Filter technologies’ ,IEEE Microwave magazine 2009

3. Harame, ‘Semiconductor Technology Choices for UWB Systems’ ,IEEE 2005

4. Idriss, A; Moorfeld R, “Performance of Coherent and Non-coherent Receivers of UWB” ,WOCN 2005

5. Immoreev, ‘Practical Applications of UWB Technology’ ,IEEE A&E Systems 2010

6. Kohno R; Takizawa K, ‘Overview of Research and Development Activities in NICT UWB Consortium’ ,IEEE 2005

7. Kshetrimayum R, ‘An introduction to UWB communication systems’ ,IEEE 2009

8. Mary G.I, Prithiviraj V, ‘UWB Localization Techniques for Precision Automobile Parking System’ ,IEEE 2008

9. Miller, ‘Why UWB? A Review of Ultra wideband Technology’, Report to NETEX Project Office, DARPA 2003

10. Mungale S; Thakare R.D, ‘Comparative Evaluation of Different Modulation Schemes in UWB’ , ICETET 2009

11. Nekoogar, ‘Introduction to Ultra-Wideband Communications’ ,PHI 2006

12. Siwiak, ‘UWB Radio technology’ ,Wiley 2004

13. Staderini, ‘UWB Radars in Medicine’ ,IEEE AESS Systems Magazine 2002

14. Tsang T.K.K; El-Gamal M.N, ‘UWB Communications Systems :An Overview’ ,IEEE 2005

15. Wood; Aiello, ‘Essentials of UWB’ ,Cambridge 2008

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18. Site : http://www.timedomain.com/

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APPENDIX

AWICS UWB Aircraft Inter communications system

BToUWB- Bluetooth over Ultra Wideband

Bluetooth connection’s data over a software implemented UWB Medium Access Control (MAC) and simulated Physical (PHY) layer radio channel

DRACO UWB Network Transceiver IEEE 802.15.3a UWB HDR WPAN IEEE 802.15.4a UWB LDR WSN

Sensor, positioning, and identification network (SPIN)

IEEE 802.15.6 UWB Wearable LDR WBAN ORION L-band UWB Transceiver Precision Asset Location (PAL) System UWB for detection of on-board items

inside vehicles QUPID- QUick response Perimeter Intrusion Detection

UWB radar used for guarding of objects in the room.

SPIDER GPR used as a backup sensor for a large mining vehicle

UROOF UWB Radio Over Optical Fiber for UWB Network extension

UWB Endoscope real-time diagnosis with high resolution images by UWB

UWB-MIMO UWB-based Virtual-MIMO system for cellular network to provide better spatial diversity and higher system capacity

UWB SATCOM UWB signals are radiated from satellites to the earth by which new satellite applications can be developed

UWB UMV UWB UnManned Vehicle employing Vehicular collision avoidance by SRR

Wireless USB UWB as the technology to achieve high data rates up to 480 Mbps