Seminar Report on UWB FM -CW RADAR

A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building

Abstract

Today world is going very fast in

terms of technology, and triggering to latest

technologies, one of the technologies

evolved far back is detecting humans, the

detection of human beings is done in various

ways like Imaging Techniques, Sensing

Techniques, both the imaging and sensing

techniques will work when the human is in

front of the equipment or the machine, the

disadvantage of the imaging and sensing

techniques can’t detect humans behind the

obstacle, this disadvantage evolved to detect

human beings behind the walls or obstacles

this can be achieved using RADAR. We

know that Radar is conventional and

commercial equipment that had been serving

for different purposes in different ways, the

working nature of radar helped to improve

the security more by introducing the latest

technology i.e, through the wall human

detection.

The technology through-the-wall

(TTW) radar demonstrator for the

detection and the localization of people in a

room (in a no cooperative way) with the

radar situated outside but in the vicinity of

the first wall. After modeling the

propagation through various walls and

quantifying the backscattering by the human

body, an analysis of the technical

considerations which aims at defining the

radar design is presented. Finally ultra

wideband (UWB) frequency modulated

continuous wave (FMCW) radar is

proposed, designed, and implemented. The

FM-CW Radar with an extended frequency

sweep form 0.5 to 8 GHz is presented it has

been applied to the TTW human detection.

Some representative trials show that this

radar is able to localize and track moving

people behind a wall in real time. This

Radar will enable large stand-off distance

capabilities and in depth building detection.

1. INTRODUCTION

Here we assess human detection through

the wall using UWB (Ultra Wide Band)

radars, we know that radar stands for radio

detection and ranging, i.e, using RADAR we

can find the Range, Direction and angle of

the object, radar uses electromagnetic waves

that are transmitted by the transmitter into

the air to detect the object or reflecting

material, the reflected echo signal from the

object must be in the direction of the

Receiver to find the range, there are

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different types of radars have been

developed for different applications

The detection of humans hidden by walls

or rubble, trapped in buildings on fire or

avalanche victims are of interest for rescue,

surveillance and security operations. The

problem of rescuing people from beneath the

collapsed buildings does not have an

ultimate technical solution that would

guarantee efficient detection and localization

of victims. The main techniques used are:

Cameras with long optical fibers that are

injected into the holes or fissures in the

collapsed buildings (the usability of such

devices and their efficiency depend on the

structure of collapsed building and besides,

when the victim is detected it is difficult in

the most cases to determine its actual

position). Sledge hammers are used to give a

signal to potential victims, and rescuers with

microphones are waiting for hearing the

response (obvious limitation of this method

is that unconscious people cannot be

detected. Localization of victims is a

problem as well). Search dogs are deployed

in the disaster area. They detect presence of

victims efficiently by smell, but information

about their actual positions or quantity

cannot be indicated. Moreover, dog is likely

to indicate the presence of dead person

which distracts rescuers from locations

where living people can still be found [1].

Due to the ability of electromagnetic waves

to penetrate through typical building

materials and its significant (in order of

centimeters) spatial resolution, UWB radar

is considered as preferred tool for detection

and localization of people. Detection of

human beings with radars is based on

movement detection – respiratory motions

and movement of body parts. These motions

cause changes in frequency, phase,

amplitude and periodic differences in time-

of-arrival of scattered pulses from the target,

which are result of periodic movements of

the chest area of the target [2].

Typical radar applications are listed here to

give an idea of the huge importance of

radar in our world.

Surveillance

Military and civil air traffic control, ground-

based, airborne, surface coastal,

satellitebased

Searching and tracking

Military target searching and tracking

Fire control

Provides information (mainly target

azimuth, elevation, range and velocity) to a

firecontrol

system

Navigation

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Satellite, air, maritime, terrestrial navigation

Automotive

Collision warning, adaptive cruise control

(ACC), collision avoidance

Level measurements

For monitoring liquids, distances, etc.

Proximity fuses

Military use: Guided weapon systems

require a proximity fuse to trigger the

explosive

warhead

Altimeter

Aircraft or spacecraft altimeters for civil and

military use

Terrain avoidance

Airborne military use

Secondary radar

Transponder in target responds with coded

reply signal

Weather

Storm avoidance, wind shear warning,

weather mapping

Space

Military earth surveillance, ground mapping,

and exploration of space environment

Security

Hidden weapon detection, military earth

surveillance

Through The Wall (TTW) human

detection using radar is a relatively new

topic that has been investigated in many

countries all around the world. It addresses

the ability to see behind walls in order to

detect, count, and localize people inside a

building. We would like to remain at large

stand off distances (5-10 or even 50 m) if

possible, according to the allowed emitted

power. TTW Radars utilize frequencies

ranging from UHF to S band in order to

have better wall penetration for any kind of

wall. It is further more recommended to use

ultrawideband (UWB) modulations in order

to achieve range resolution for human

localization and to deal with indoor

propogation channel. Through-the-wall

(TTW) radar technique addresses

electromagnetic “vision” behind walls in

order to detect, count, and localise people

inside a building. Considering one by one

these three objectives: detect, count, and

localise, it is possible to situate our work

among the various researches that are

ongoing in the TTW radar field.In order to

detect one or more persons in a room, it is

necessary to take into account the fact that

these people move. In fact, the radar return

coming from the human body is not high

enough compared to the backscattering of

the indoor environment to ensure detection.

So that, Doppler effect has been used

historically to detect motion through walls

[1]. Nevertheless, Doppler radar has also

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some drawbacks. The first one is its high

sensitivity to all kinds of motions bringing

false alarms. The second one is that target

localisation and Doppler filtering seems

incompatible. This is why emphasis was

made on imaging radar with the ability to

count and localise targets.Small TTW radars

based on the technology of UWB pulses

appeared since the 2000s. The famous ones

are Radarvision and then Xaver by

CAMERO. There is no publication about

them in the open literature. Besides, some

radar and signal processing specialized

laboratories have studied UWB radar

imaging or SAR imaging applied to through-

wall vision [2, 3].The work presented here

gives the last advances from our laboratory

in the “see-through” radar topic. It aims at

giving a global approach of the TTW radar

detection. It shows step by step the design

process after radar modelling: from

theoretical background to radar realization

followed by experimental assessment.

In Section 2, the through-the-wall

propagation physics has been studied by

simulation and also assessed by

measurements. Then, in Section 3, the

backscattering strength of the human body is

quantified in an anechoic chamber with

various people under test. Section 4 is

centred on an analysis of technical

considerations which aims at defining the

best radar design. And finally, Sections 5

and 6 present the radar implementation and

a trial of people detection and localization

through a wall.

So many radars have been developed to

detect ranges of any distinct object, the

various radars are

1. Pulsed Doppler radar

2. Continous wave radar

3. FM-CW radar

4. MTI Radar

5. Phased Array Radar

6. Synthetic Aperture Radar

7. Bi Static and Multi Static radar

8. Passive Radar

9. Multimode Radar

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2. Literature Survey

Before moving into the different types of

radars used for different applications, let’s

check the radar frequencies, Bands,

Wavelengths and its applications.

2.1. Radar Frequencies, - Bands, Wavelength and Applications

Band

Frequency

Wavelength

Application

HF

3-30 Mhz

10m-100m

Coastal radar systems, over-the-horizon (OTH) radars; ’high frequency’

P 30 to 300 Mhz

1m to 10 m

’P’ for ’previous’, applied retrospectively to early radar systems

UHF

300-1000Mh

z

0.3-1m Very long range (e.g. ballistic missile early warning), ground

penetrating, foliage penetrating; ’ultra high frequency’

L 1 – 2 GHz

15 cm to 30 cm

Long-range air traffic control and surveillance; 'L' for 'long'

S 2 – 4 GHz

7.5 cm to 15 cm

Terminal air traffic control, long-range weather, marine radar; 'S' for 'short'

C 4 – 8 GHz

3.75 cm to 7.5 cm

Satellite transponders; a compromise (hence 'C') between X and S bands; weatherradar

X 8 – 12 GHz

2.5 cm to 3.75 cm

Missile guidance, marine radar, weather, medium-resolution mapping and ground surveillance; in the USA the narrow range 10.525 GHz ± 25 MHz is used for airport radar. Named X band

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because the frequency was kept secret during World War 2.

KU 12 – 18 GHz

1.67 cm to 2.5 cm

High-resolution mapping, satellite altimetry; frequency just under K band (hence 'u')

K 18 – 27 GHz

1.11 – 1.67 cm

K band is used by meteorologists for detecting clouds and by police for detecting speeding motorists. K band radar guns operate at 24.150 ± 0.100 GHz. Automotive radar uses 24 – 26 GHz.

Ka 27 – 40 GHz

0.75 cm to 1.11 cm

Mapping, short range, airport surveillance; frequency just above K band (hence 'a'); photo radar, used to

trigger cameras that take pictures of license plates of carsrunning red lights, operates at 34.300 ± 0.100 GHz

Mm 40 – 300 GHz

1 mm to 7.5 mm

Millimeter band, subdivided as below. The letter designators appear to be random, and the frequency ranges dependent on waveguide size. Multiple letters are assigned to these bands by different groups

Q 40 – 60 GHz

5 mm to 7.5 mm

Used for military communications

V 50 – 75 GHz

4 mm to 6 mm

Very strongly absorbed by the atmosphere

W 75 – 110 GHz

2.7 mm to 4 mm

76 GHz LRR and 79 GHz SRR automotive

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radar, high-resolution meteorologicalobservation and imaging

2.2. Radar Equation

The acronym RADAR stands for Radio Detection And Ranging. Figure 1 shows the basic principle.

Figure 1: Basic principle of Radar and its parameters

An electromagnetic wave of power Pt is

transmitted to a flying object, for example to a

plane and is partly reflected back to the antenna

with the receiving power Pr. From the time

delay between the transmitted and received

signal the distance to the plane can be

calculated. Additional information can be gained

from the frequency shift of the received signal,

which is proportional to the speed of the plane.

Receiving a signal of sufficient power by an

adequate power to noise ratio is the biggest

challenge of radar systems. The so called .Radar

Equation. gives hints on the power relations

within the system as indicated in Figure1. The

Radar Equation delivers the received power Pr

as result. According to the Radar Equation

following independent parameters determine the

received power Pr.

Pt: The power transmitted by the antenna,

dimension is dBm. Numeric examples : 63

dBm for real world Radar applications, 13

dBm for laboratory tests

G: Gain of the transmitting antenna,

dimension in dBi. The parameter determines

how much the radiation beam of the antenna

is focused toward the direction of the target.

Numeric examples are 12 dBi for a BiQuad

antenna and 70 dBi for a highly focusing

parabolic antenna.

σ is The wavelength of the transmitted

signal, dimension in meter. The wavelength

can be directly calculated from the

frequency. Numeric examples: 0.03 m for a

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10 GHz signal and 0.12 m for a 2.54 GHz

signal

Radar cross section, RCS, is a virtual area

representing the intensity of the reflection.

Not all of the radiated power is reflected

back to transmitting antenna, as indicated by

the small waves close to the plane in Figure

1. The .Sigma. ( ) of the objects determines

the virtual area of the reflecting object

(plane) from which all of the incoming

radiation energy is reflected back to the

antenna. The dimension is square

meter, .m2. in short. Practical examples are

12 m2 for a commercial plane, 1 m2 for a

person or 0.01 m2 for a bird. Refer to [18],

page 6665 for further

examples.

R: Distance between the transmitting

antenna and the reflecting object. Dimension

in m. Numeric examples are 8000 m for real

world applications or 5 m for laboratory

conditions. It has to be stressed that this

parameter reduces the result, i.e. the

received signal by the power of 4, with the

effect that far distant objects are providing

only a small amount of received power.

Table 1: Parameters of Radar Equitation and two

examples

Parame

ter

Abbrevi

ation

Value

,

Exam

ple 1

Value

Exam

ple 2

Uni

t

Transm

itted

power

Pt 63 13 dB

m

Gain of

transmi

t

antenna

G 28 12 dBi

Wavele

ngth

(freque

ncy)

(f) 0.03

(10*1

09)

0.12

(2.5*1

09)

m(

Hz)

Radar

cross

section

12 0,3 m2

Distanc

e

R 8114 5 m

Receive

d

power,

linear

Pr 1 17.4*

103

pW

Receive

d

power,

logarith

mic

Prlog -90 -48 dB

m

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Example 1 shows a a real world example,

derived from [Pozar], example 2 shows a

radar application which can be realized

under laboratory conditions for example

in an anechoic chamber.

Example 1 read in clear text : A radar

transmitting antenna with gain of 28 dBi is

transmitting an electromagnetic wave at 10

GHz with a power of 63 dBm to a plane in a

distance of about 8000 m. The plane has a

radar cross section of 12 m2 . By means of

the Radar Equation the received power back

at the antenna is calculated to -90 dBm.

Example 2 read in clear text: In a radar test

laboratory implemented in an anechoic

chamber a test transmitter provides 13 dBm

to a matched antenna of 12 dBi with a

frequency of 2.5 GHz. The reflecting object

with a cross section of 0.3 m2 is located in 5

m distance from the transmitting antenna.

According to the Radar Equation the test

receiver is going to receive a reflected signal

of -48 dBm.

When comparing example 1 to example 2

we can conclude that despite much bigger

transmitting power, better transmit antenna

gain and bigger radar cross section in

example 1 the received reflected power of

example 1 is almost 50 dB lower than the

received signal of example 2. The reason is

the smaller wavelength lambda which

affects the result by a power of 2 and

especially the bigger distance R of example

1 which affects the result by a power of 4.

Small wavelengths, i.e. high frequencies are

aimed for in most radar systems, especially

in antenna arrays, because of the resulting

small antenna size. It is obvious also, that in

radar technology one has to deal with very

small receiving power especially for far

distant objects.

2.3. Common Radar types for

Common Applications

2.3.1.Simple Pulse (Range) and Pulse Doppler (Speed/Range)Radar

Basic principle of a simple pulse radar system

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A simple pulse radar system only provides

range (plus direction) information for a

target based

on the timing difference between the

transmitted and received pulse. It is not

possible to

determine the speed. The pulse width

determines the range resolution.

Direction information with azimuth angle determination in a radar system with a rotary

antenna

The direction information (azimuth angle) is

determined from the time instant of the

receive pulse with reference to the

instantaneous radiation direction of the

rotating antenna. The important

measurements on (non-coherent) radar

equipment of this sort are the range accuracy

and resolution, AGC settling time for the

receiver, peak power, frequency stability,

phase noise of the LO and all of the pulse

parameters.

The AGC circuit of the receiver

protects the radar from overload conditions

due to nearby collocated radars or jamming

counter measures. The attack and decay time

of the AGC circuit can be varied based on

the operational mode of the radar. Since the

roundtrip of a radar signals travels

approximately 150 meters per microsecond,

it is important to measure the response of the

AGC for both amplitude and phase response

when subject to different overload signal

conditions. The measured response time will

dictate the minimum detection range of the

radar.

Pulse Doppler radar

A pulse Doppler radar also provides

radial speed information about the target in

addition to range information (and direction

information). In case of coherent operation

of the radar transmitter and receiver, speed

information can be derived from the pulse-

to-pulse phase variations. I/Q demodulators

are normally used. The latest pulse Doppler

radar systems normally use different pulse

repetition frequencies (PRF) ranging from

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several hundred Hz up to 500 kHz in order

to clarify any possible range and Doppler

ambiguities. More advanced pulse Doppler

radar systems also " use "staggered PRF, i.e.

the PRF changes on an ongoing basis to get

rid of range ambiguity and reduce clutter as

well. Important criteria for achieving good

performance in pulse Doppler radar systems

include very low phase noise in the LO, low

receiver noise and low I/Q gain phase

mismatch (to avoid "false target indication")

in addition to the measurement parameters

listed above. When measuring the pulse-to-

pulse performance of a radar transmitter, it

is important to understand the variables that

can impact the uncertainty of the

measurement system for accurate Doppler

measurements:

Signal-to-noise ratio of the signal -

the better the signal to noise ratio of

the signal, the lower

the uncertainty due to noise

contribution.

Bandwidth of the signal - the

bandwidth of the IF acquisition

system must be sufficient to

accurately represent the risetime of

the pulsed signal, however too much

bandwidth can

result in added noise contribution

uncertainty.

Reference (or timebase) clock

stability.

Jitter or uncertainty due to the

measurement point of the rising edge

of the signal . rising edge

interpolation or signals that have

changing edges impact this

uncertainty.

Overshoot and preshoot of the rising

and falling edges . any ringing on the

rising and falling edges can impact

the measurement points adversely on

a pulse to pulse basis. It is important

that the measurement point, or the

average set of measurement points,

are sufficiently far

away in time from the leading and

falling edges of a pulse. Applying a

Gaussien filter to smooth the impact

of the rising and falling edges can

reduce this phenomena and is often

implemented in the Doppler

measurement system of a radar

receiver.

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Time between measured signals . due

to the PRI of the measured signal,

the close-in phase noise of the

measurement system needs to be

considered due to the integration

time at lower offset frequencies.

The same variables can also

contribute to the uncertainty in the

signal generator when testing the

receiver circuit and Doppler

measurement accuracy.

Continuous Wave (CW) Radar:

A continuous wave (CW) radar

system with a constant frequency can be

used to measure speed.However, it does not

provide any range (distance) information. A

signal at a certain frequency is transmitted

via an antenna. It is then reflected by the

target (e.g. a car) with a certain Doppler

frequency shift. This means that the signal’s

reflection is received on a slightly different

frequency. By comparing the transmitted

frequency with the received frequency, we

can determine the speed (but not the range).

Here, a typical application is radar for

monitoring traffic.

Radar motion sensors are based on the same

principle, but they must also be capable of

detecting slow changes in the received field

strength due to variable interference

conditions that may exist.

Radar speed traps operated by the

police use this same technology. Camera

systems take a picture if a certain speed is

exceeded at a specified distance from the

target.

Mobile traffic monitoring radar

MultaRadar CD - Mobile speed radar for speed

enforcement from Jenoptic

There are also military applications:

CW radars are also used for target

illumination. This is a straightforward

application: The radar beam is kept on target

by linking it to a target tracking radar. The

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reflection from the target is then used by an

antiaircraft missile to home in on the target.

CW radars are somewhat hard to detect.

Accordingly, they are classified as low-

probability-of intercept radars.

CW radars lend themselves well to

detecting low-flying aircraft that attempt to

overcome an enemy’s air defense by

"hugging the ground". Pulsed radar has

difficulties in discriminating between

ground clutter and low-flying aircraft. CW

radar can close this gap because it is blind to

slow-moving ground clutter and can

pinpoint the direction where something is

going on. This information is relayed to co-

located pulse radar for further analysis and

action. [7]

The disadvantage of CW radar is that

it cannot detect the Range due to Narrow

Bandwidth of the transmitted signal, to

measure the range we are moving forward to

the Frequency modulated transmitted signal,

which can be used to find the range of ay

distinct object.

FM-CW Radar ( Frequency

Modulated – Continuous Wave)

The disadvantage of CW radar

systems is that they cannot measure range

due to the lack of atiming reference.

However, it is possible to generate a timing

reference for measuring the rangeof

stationary objects using what is known as

"frequency-modulated continuous wave"

(FMCW) radar. This method involves

transmitting a signal whose frequency

changes periodically. When an echo signal

is received, it will have a delay offset like in

pulse radar. The range can be determined by

comparing the frequency. It is possible to

transmit complicated frequency patterns

(like in noise radar) with the periodic

repetition occurring at most at a time in

which no ambiguous echoes are expected.

However, in the simplest case basic ramp or

triangular modulation is used, which of

course will only have a relatively small

unambiguous measurement range.

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Basic principle of FMCW radar. The target’s velocity is calculated based on the measured delay

tbetween the transmit signal and the received

signal, whereas the frequency offset f gives the

range

This type of range measurement is

used, for example, in aircraft to measure

altitude (radio altimeter) or in ground

tracking radar to ensure a constant altitude

above ground. One benefit compared to

pulse radar is that measurement results are

provided continuously (as opposed to the

timing grid of the pulse repetition

frequency). FMCW radar is also commonly

used commercially for measuring distances

in other ways, e.g. level indicators.

Automotive radar is in most cases FMCW

radar too

Moving-Target Identification (MTI)

Radar

The idea behind MTI radar is to

suppress reflected signals from stationary

and slow-moving objects such as buildings,

mountains, waves, clouds, etc. (clutter) and

thus obtain an indication of moving targets

such as aircraft and other flying objects.

Here, the Doppler effect is exploited, since

signals reflected by targets moving radially

with respect to the radar system exhibit an

offset vs. the transmitted frequency which is

proportional to their speed (e.g. in linear FM

radar).

In pulse radar systems, the pulses

reflected by moving objects have a variable

phase from pulse to pulse referenced to the

phase of the transmitted pulses.

3. UWB RADAR

Technology

Ultra Wideband technology has been an

extremely evolving technology because of

its appealing characteristics like achieving

high data rates, more capacity as compared

to narrowband systems, and co-existence

with the existing narrowband wireless

technologies. A signal is categorized as

UWB if its bandwidth is very large with

respect to its center frequency. That results

that the fractional bandwidth should be very

high. The FCC defines UWB as a signal

with either a fractional bandwidth of 20% of

the center frequency or 500 MHz (when the

center frequency is above 6 GHz). The

formula proposed by the FCC commission

for calculating the fractional bandwidth is

[3, 4]: Where fH represents the upper

frequency of the -10 dB emission limit and

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fL represents the lower frequency limit of

the -10dB emission limit

UWB is based on the generation of very

short duration pulses of the order of

picoseconds. The information of each bit in

the binary sequence is transferred using one

or more pulses by code repetition. This use

of number of pulses increases the robustness

in the transmission of each bit. In

UWBcommunications there is no carrier

used and hence all the references are made

with respect to the center frequency. In Ultra

wideband communications, a signal with a

much larger bandwidth is transmitted with a

reduced power spectral density. This

approach has a potential to produce signal

which has higher immunity to interference

effects and improved time of arrival

resolution. Ultra wide band communications

employ the technique of impulse radio.

Impulse radio communicates with the help

of base band pulses of very short duration of

the order of nanoseconds, thereby spreading

the energy of the signal from dc to few

gigahertz. The fact that the impulse radio

system operates in the lowest possible

frequency band that supports its wide

transmission bandwidth means that this

radio has the best chance of penetrating

objects which become opaque at higher

frequencies. Impulse radios operating in the

highly populated frequency range below a

few gigahertz must contend with a variety of

interfering signals. They must also guarantee

that they do not interfere with the narrow-

band radio systems operating in dedicated

bands. These requirements necessitate the

use of spread spectrum techniques. A means

of spreading the spectrum of the ultra-

wideband pulses is to employ time hopping

with data modulation accomplished by

additional pulse position modulation at the

rate of many pulses per data symbol. The

use of signals with gigahertz bandwidth

means that multipath is resolvable down to

path differential delays on the order of

nanoseconds or less i.e. down to path length

differentials on the order of foot or less. This

significantly reduces fading effects even in

indoor environments. The advantages of

UWB over conventional narrowband

systems are [3]:

Large Instantaneous bandwidth that

enables fine time resolution for

network time

distribution, precision location

capability, or use as a radar.

Short duration pulses that provide

robust performance in dense

multipath

15


environments by exploiting more

resolvable paths.

Low power spectral density that

allows coexistence with existing

users and has a

Low Probability of Intercept (LPI).

Data rate may be traded for power

spectral density and multipath

performance

3.1Salient Features of Ultra-wideband Radars

3.1.1 High Data rate

UWB can handle more bandwidth-

intensive applications like streaming video,

than either 802.11 or Bluetooth because it

can send data at much faster rates. UWB

technology has a data rate of roughly 100

Mbps, with speeds up to 500 Mbps, This

compares with maximum speeds of 11 Mbps

for 802.11b (often referred to as Wi-Fi)

which is the technology currently used in

most wireless LANs; and 54 Mbps for

802.11a, which is Wi-Fi at 5MHz. Bluetooth

has a data rate of

about1Mbps.

Maximum range and data rate of different

wireless technologies

Low power consumption

UWB transmits short impulses

constantly instead of transmitting modulated

waves continuously like most narrowband

systems do. UWB chipsets do not require

Radio Frequency (RF) to Intermediate

Frequency (IF) conversion, local oscillators,

mixers, and other filters. Due to low power

consumption,battery-powered devices like

cameras and cell phones can use in UWB

[3].

Interference Immunity

Due to low power and high

frequency transmission, USB’s aggregate

16


interference is “undetected” by narrowband

receivers. Its power spectral density is at or

below narrowband thermal noise floor. This

gives rise to the potential that UWB systems

can coexist with narrowband radio systems

operating in the same spectrum without

causing undue interference [3].

High Security

Since UWB systems operate below

the noise floor, they are inherently covertand

extremely difficult for unintended users to

detect [3].

Reasonable Range

IEEE 802.15.3a Study Group defined

10 meters as the minimum range at speed

100Mbps However, UWB can go further.

The Philips Company has used its Digital

Light Processor (DLP) technology in UWB

device so it can operate beyond 45 feet at 50

Mbps for four DVD screens [3].

Low Complexity, Low Cost

The most attractive of UWB’s

advantages are of low system complexity

and cost. Traditional carrier based

technologies modulate and

demodulatecomplex analog carrier

waveforms. In UWB, Due to the absence of

Carrier, the transceiver structure may be

very simple. The techniques for generating

UWB signals have existed for more than

three Decades. Recent advances in silicon

process and switching speeds make UWB

system as low-cost. Also home UWB

wireless devices do not need transmitting

power amplifier. This is a great advantage

over narrowband architectures that require

amplifiers with significant power back off to

support high-order modulation waveforms

for high data rates [3].

Large Channel Capacity

The capacity of a channel can be

express as the amount of data bits

transmission/second. Since, UWB signals

have several gigahertz of bandwidth

available that can produce very high data

rate even in gigabits/second. The high data

rate capability of UWB can be best

understood

by examining the Shannon’s famous

capacity equation:

𝐶 = 𝐵 log!(1 + !

!) (1.4)

17


Where C is the channel capacity in

bits/second, B is the channel bandwidth in

Hz, S is the signal power and N is the noise

power. This equation tells us that the

capacity of a channel grows linearly with the

bandwidth W, but only logarithmically with

the signal power S. Since the UWB channel

has an 19 abundance of bandwidth, it can

trade some of the bandwidth against reduced

signal power and interference from other

sources. Thus, from Shannon’s equation we

can see that UWB systems have a great

potential for high capacity wireless

communications [7].

Resistance to Jamming

The UWB spectrum covers a huge

range of frequencies. That’s why, UWB

signals are relatively resistant to jamming,

because it is not possible to jam every

frequency in the UWB spectrum at a time.

Therefore, there are a lot of frequency range

available even in case of some frequencies

are jammed.

Scalability

UWB systems are very flexible

because their common architecture is

software re-definable so that it can

dynamically trade-off high-data throughput

for range [6].

Application of UWB

Wireless technology is playing now

main role in our daily lives. In recent years,

demand of higher quality and faster delivery

of data is increasing day by day. The need of

more speed and quality brought up many

wireless solutions for short rang

communication. The family of Wi-Fi

standards (IEEE802.11), Zigbee

(IEEE802.15.4) and the recent standard

802.15.3, which are used for wireless local

area networks (WLAN) and wireless

personal area networks (WPAN), can’t meet

the demands of applications that needs much

higher data rate. UWB connection function

as cable replacement with date rate more

than 100 Mbps. Applications of UWB can

be categorized in following section.

Imaging Systems

UWB was firstly used by military

purpose to identify the buried installations.

In imaging system emission of UWB is used

as illuminator similar to radar pulse. The

receiver receives the signal and the output is

processed using complex time and

frequency functions to differentiate between

materials at varying distance. The lower part

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of radio spectrum < 1 GHz have ability to

penetrate the ground and solid surfaces. This

property makes UWB a best choice for

detection of buried objects and public

security and protection organizations.

UWB plays an important role in

medical imagine and human body analysis.

Now a day’s ultra wideband radars are used

for heart treatment. All of inner body parts

of human being can be imaged by adjusting

the emitting pulse power [21].

Radar Systems

In early days military used UWB

technology in radar system to detect the

object in high-density media like ground, ice

and air targets. Research and studies in this

area found, radar can be used everywhere

where we need sensing of moving objects.

Radar systems can be installed in vehicle to

avoid accident during driving and parking.

UWB radars can be used in guarding

systems as alarm sensors to detect

unauthorized entrance into the territory.

These radars can be used to find objects or

peoples in collapsed buildings by detecting

the movement of person; but in case person

is not moving, it can still be detected by

heart beat and thorax beats. Police

department can use such radars to find

criminals hidden in shelters. These radars

are able to measure the patient’s cardiac and

breathing activity in hospitals as well as at

home [21].

Home Networks

In a home environment, variety of

devices are operating such as DVD players,

HDTVs, STBs, Personal video recorders,

MP3 players , digital cameras, camcorders

and others. The current popular usage of

home networking is sharing date from PC to

PC and from PCs to peripherals. Customers

are demanding multiplayer gaming and

video distributions in home network. These

all devices are connected using wires to

share contents at high speed. UWB is a wire

replacement technology provides high

bandwidth more than 100 Mbps. These all

devices can be connected in a home network

to share multimedia, printers, scanners and

etc. UWB can connect a plasma display or

HDTV to a DVD or STB without using any

cable. UWB also enables multiple streaming

to multiple devices simultaneously, that

allows viewing same or different content on

multiples devices. For example, movie

content can be shared on different display

devices in different rooms [1] [3]. The home

networks are directly connected to a

broadband through a residential gateway.

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This approach is cost effective but is

ineffective for whole house coverage.

Cables are installed to connect different

devices with Internet in a home

environment. With a right UWB solution

Internet traffic from multiple users in a

home can be routed to single broadband

connection. UWB enable devices can be

connected in an ad-hoc manner like

Bluetooth to share contents. For example a

camera can be connected to a printer directly

to print pictures; MP3 player can be

connected to another MP3 player and shared

music.

Sensor Networks

Wireless sensor networks are an

important area of communication. Sensor

networks have many applications, like

building control, surveillance, medical,

factory automation etc. Sensor networks are

operated under many constraints such as

energy consumption, communication

performance and cost. In many applications

sensor size is also considered to be smaller.

UWB use pulse transmission, with very low

energy consumption. This property enables

us to design very simple transmitters and

thus long time battery operated devices.

These sensors can be used in locating

hospitals, tracking and communication

systems. These systems enable us to locate

and track objects including facilities,

equipment’s, nurses, doctors and patients in

a hospital [2]. Furthermore these systems

can be used in factories to track

equipment’s, employees and visitors.

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21


The Future of Radar Developments

In the future, we can expect to

encounter multisensory systems that

combine radar and infrared (or other)

systems[11]. This will make it possible to

combine the benefits of the different types

of systems while suppressing certain

weaknesses [11].

Military onboard radar systems will

be increasingly confronted with the stealth

characteristics of advanced aircraft. The

contradiction between the different

requirements imposed on aircraft must be

solved (i.e. planes should exhibit stealth

properties while not revealing their position

through the use of onboard radar). One

possibility involves the use of a bistatic

radar system with a separate illuminator and

only a receiver on-board the aircraft.

In the future, radar antennas will in

many cases no longer exist as discrete

elements with suitable radomes. Instead,

they will be integrated into the geometrical

structure of the aircraft, ship or other

platform that contains them. The next

generation of AESA radars used on-board

aircraft will have more than one fixed array

in order to be able to handle greater spatial

angles.

Finally, the speed of the digital back-end

equipment handling the radar raw data will

need to

increase i.e. through parallel processing in

order to handle data rates as needed for high

resolution radar operating modes.[12]

REFERENCES

1. Merrill I. Skolnik,1990, Radar

Handbook, Second Edition McGraw-

Hill

2. Merrill I. Skolnik,1990, Radar

Handbook, Second Edition McGraw-

Hill, Chapter 7

3. http://www.radartutorial.eu/

index.en.html


rrp.117.html

5. http://de.wikipedia.org/wiki/

Synthetic_Aperture_Radar

6. http://keydel.pixelplaat.de/uploads/

File/vorlesung07-08/SAR.pdf

7. http://www.h2g2.com/

approved_entry/A743807

8. http://www.armedforces.co.uk/

releases/raq43f463831e0b7

9. http://www.pa.op.dlr.de/poldirad/

BISTATIC/index.html

10. Silent Sentry.Passive Surveillance

22


11. http://defense-update.com/

20110721_super-hornets-future-eo-

radar

12. radar-technology-looks-to-the-

future.html


06.antennas/an17.en.html

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