My New Final Project

8/3/2019 My New Final Project

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A

PROJECTOn

Study of SMART ANTENNA

Submittedin partial fulfillment ofthe requirements

For the award of

ADVANCED DIPLOMA IN ELECTRONICS AND TELECOMMUNICATION

ENGINEERING

TO

SINGAPORE POLYTECHNIC

For the academic Year 2011-2012

By

NATARAJ RANJITH KUMAR

P 1147360

Under the guidance of

Mr A.L.SATHYAPRAKASH

Dept of EEE


SINGAPORE


500 Dover RoadSingapore 139651


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ACKNOWLEDGEMENT

I am pursuing my final year program in Advanced

Diploma in Electronics & Telecommunications Engineering andvery much gained and encouraged by the professors and staffs ofSingapore polytechnic & it would be an initial step for me tostartup, develop & achieve my career. The course also upgradedmy previous theoretical & practical knowledge.

I would like thank to my Prof. MR.A.L.SATHYAPRAKASH, Head of the department Electronics andTelecommunications Engineering , singapore polytechnic ,singapore. For his kind effort and motivate, guidance on my

completion of project, I also thanks for him on spending hisvaluable and precious time on clearing various discussion &Queries.


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ABSTRACT

The fundamental idea behind smart antennais to improve the performance of the wirelesscommunication system by increasing the gain in a chosendirection. This can be achieved by pointing the main lobes ofthe antenna-beam patterns towards the desired users. Smartantenna system combines multiple antenna elements with asignal processing capability to automatically optimise itsradiation and/or reception pattern in response to the signalenvironment.

In addition to pointing the direction of the mainlobe towards a chosen user the smart antenna system canautomatically steer one or more nulls of the directivity patterntowards one or several sources of interferences. There are severalbenefits of using a smart antenna system for a wireless systemand among these are the following: larger covering area,increased SNR and capacity, saving energy for the sameperformances, providing spatial diversity etc. In this paper bothswitched and adaptive beamforming techniques are analysed inorder to point out the advantages of using smart antennatechnique in wireless communications systems.


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TABLE OF CONTENT

Acknowledgements

Abstract

1. Introduction

2. antenna and antenna system

2.1 antenna

2.1.1 omnidirectional antenna

2.1.2 directional antenna

2.2 antenna system

2.2.1 sectorised system

2.2.2 diversity system

2.2.3 switched diversity

2.2.4 diversity combining

3. smart antenna

3.1 introduction of smart antenna

3.2 history of smart antenna

3.3 types of smart antenna

3.3.1 adaptive array

3.3.2 switched beam

3.4 relative benefits of switched beam and

Adaptive array system

3.5 working of smart antenn

3.6 categories of smart antenna

3.7 functions of smart antenna


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3.7.1 beamforming

3.7.2 direction of arrival(doa)

3.8 parameters affecting antenna

Performance

3.9 application of smart antenna

3.10 advantages and disadvantages of smart

Antenna

3.11 features and benefits of smart antenna

4.Conclusion

5.References


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Introduction

Wireless Communication is growing with a very rapid rate for several years.

The progress in radio technology enables new and improved services.

Current wireless services include transmission of voice, fax and low-speed

data. More bandwidth consuming interactive multimedia services like video-

on demand and internet access will be supported in the future.

Wireless systems that enable higher data rates and higher capacities are a

pressing need. Wireless networks must provide these services in a wide

range of environments, dense urban, suburban, and rural areas.

Because the available broadcast spectrum is limited, attempts to increase

traffic within a fixed bandwidth create more interference in the system and

degrade the signal quality.

The solution to this problem is SMART ANTENNA. Today's modern wireless

mobile communications depend on adaptive "smart" antennas to provide

maximum range and clarity. With the recent explosive growth of wireless

applications, smart antenna technology has achieved widespread

commercial and military applications.

There is an ever-increasing demand on mobile wireless operators to provide

voice and high-speed data services. At the same time, operators want to

support more users per basestation in order to reduce overall network cost

and make the services affordable to subscribers. As a result, wireless

systems that enable higher data rates and higher capacities have become

the need of the hour.


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Antenna and Antenna

System

2.1 Antenna

An antenna (or aerial) is a transducer designed to transmit or receive

electromagnetic waves. In other words, antennas convert electromagnetic

waves into electrical currents and vice versa. Antennas are used in systems

such as radio and television broadcasting, point-to-point radio

communication, wireless LAN, radar, and space exploration. Antennas are

most commonly employed in air or outer space, but can also be operated

under water or even through soil and rock at certain frequencies for short

distances.

Physically, an antenna is simply an arrangement of one or more conductors,

usually called elements in this context. . In transmission, an alternating

current is created in the elements by applying a voltage at the antenna

terminals, causing the elements to radiate an electromagnetic field. In

reception, the inverse occurs: an electromagnetic field from another source

induces an alternating current in the elements and a corresponding voltage

at the antenna's terminals. Some receiving antennas (such as parabolictypes) incorporate shaped reflective surfaces to collect EM waves from free

space and direct or focus them onto the actual conductive elements.

There are two fundamental types of antenna directional patterns, which,

with reference to a specific three dimensional (usually horizontal or vertical)

plane are either:

1. Omni-directional (radiates equally in all directions), such as a verticalrod.

2. Directional (radiates more in one direction than in the other).


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2.1.1- Omnidirectional Antenna

Omni-directional usually refers to all horizontal directions with reception

above and below the antenna being reduced in favor of better reception (and

thus range) near the horizon .

Since the early days of wireless communications, there has been the simple

dipole antenna, which radiates and receives equally well in all directions. To

find its users, this single-element design broadcasts omnidirectionally in a

pattern resembling ripples radiating outward in a pool of water. While

adequate for simple RF environments where no specific knowledge of the

users' whereabouts is available, this unfocused approach scatters signals,

reaching desired users with only a small percentage of the overall energysent out into the environment.

Figure 2.1:- Omnidirectional Antenna and Coverage Patterns

Given this limitation, omnidirectional strategies attempt to overcome

environmental challenges by simply boosting the power level of the signals

broadcast. In a setting of numerous users (and interferers), this makes a

bad situation worse in that the signals that miss the intended user become

interference for those in the same or adjoining cells.

In uplink applications (user to base station), omnidirectional antennas offer

no preferential gain for the signals of served users. In other words, users

have to shout over competing signal energy. Also, this single-element


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approach cannot selectively reject signals interfering with those of served

users and has no spatial multipath mitigation or equalization capabilities.

Omnidirectional strategies directly and adversely impact spectral efficiency,

limiting frequency reuse. These limitations force system designers and

network planners to devise increasingly sophisticated and costly remedies.

In recent years, the limitations of broadcast antenna technology on the

quality, capacity, and coverage of wireless systems have prompted an

evolution in the fundamental design and role of the antenna in a wireless

system.

2.1.2- Directional Antenna

A "directional" antenna usually refers to one focusing a narrow beam in a

single specific direction. A single antenna can also be constructed to have

certain fixed preferential transmission and reception directions. As an

alternative to the brute force method of adding new transmitter sites, many

conventional antenna towers today split, or sectorize cells. A 360 area is

often split into three 120 subdivisions, each of which is covered by a

slightly less broadcast method of transmission

All else being equal, sector antennas provide increased gain over a restricted

range of azimuths as compared to an omnidirectional antenna. This is

commonly referred to as antenna element gain and should not be confused

with the processing gains associated with smart antenna systems.

While sectorized antennas multiply the use of channels, they do not

overcome the major disadvantages of standard omnidirectional antenna

broadcast such as co-channel interference.

All antennas radiate some energy in all directions in free space but careful

construction results in substantial transmission of energy in a preferred

direction and negligible energy radiated in other directions.


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Figure 2.2 - Directional Antenna

and Coverage Pattern

2.2- Antenna System

First, its physical design can be modified by adding more elements.

Second, the antenna can become an antenna system that can be designed to

shift signals before transmission at each of the successive elements so that

the antenna has a composite effect. This basic hardware and software

concept is known as the phased array antenna.

2.2.1- Sectorised System

Sectorized antenna systems take a traditional cellular area and subdivide it

into sectors that are covered using directional antennas looking out from the

same base station location. Operationally, each sector is treated as a

different cell, the range of which is greater than in the omnidirectional case.

Sector antennas increase the possible reuse of a frequency channel in such

cellular systems by reducing potential interference across the original cell,


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and they are widely used for this purpose. As many as six sectors per cell

have been used in practical

service. When combining more than one of these directional antennas, the

base station can cover all directions.

Figure 2.3 - Sectorized

Antenna and

Coverage

Patterns

2.2.2- Diversity System

In the next step toward smart antennas, the diversity system incorporates

two antenna elements at the base station, the slight physical separation

(space diversity) of which has been used historically to improve reception by

counteracting the negative effects of multipath.

Diversity offers an improvement in the effective strength of the received

signal by using one of the following two methods:-

A).Switched Diversity

B).Diversity combining.

Diversity antennas merely switch operation from one working element to

another. Although this approach mitigates severe multipath fading, its use

of one element at a time offers no uplink gain improvement over any other

single-element approach. In high-interference environments, the simple

strategy of locking onto the strongest signal or extracting maximum signal


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power from the antennas is clearly inappropriate and can result in crystal-

clear reception of an interferer rather than the desired signal.

The need to transmit to numerous users more efficiently without

compounding the interference problem led to the next step of the evolution

antenna systems that intelligently integrate the simultaneous operation of

diversity antenna elements.

2.2.3- Switched Diversity

Assuming that at least one antenna will be in a favorable location at a given

moment, this system continually switches between antennas (connects each

of the receiving channels to the best serving antenna) so as always to use

the element with the largest output. While reducing the negative effects of

signal fading, they do not increase gain since only one antenna is used at a

time.

Figure 2.4 - Switched Diversity Coverage with Fading and Switched Diversity

.


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2.2.4- Diversity Combining

This approach corrects the phase error in two multipath signals and

effectively combines the power of both signals to produce gain. Other

diversity systems, such as maximal ratio combining systems, combine the

outputs of all the antennas to maximize the ratio of combined received

signal energy to noise.

Figure 2.5. Combined Diversity Effective Coverage Pattern with

Single Element and Combined Diversity


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Smart Antenna

3.1- Introduction of Smart Antenna

Contrary to the name smart antennas consist of more than an antenna. A

Smart Antenna is an antenna system which dynamically reacts to its

environment to provide better signals and frequency usage for wireless

communications. There are a variety of smart antennas which utilize

different methods to provide improvements in various wireless applications.

This report aims to explain the main types of smart antennas and there

advantages and disadvantages.

The concept of using multiple antennas and innovative signal processing to

serve cells more intelligently has existed for many years. In fact, varying

degrees of relatively costly smart antenna systems have already been applied

in defense systems. Until recent years, cost barriers have prevented their

use in commercial systems. The advent of powerful low-cost digital signal

processors (DSPs), general-purpose processors (and ASICs), as well as

innovative software-based signal-processing techniques (algorithms) have

made intelligent antennas

practical for cellular communications systems.

Today, when spectrally efficient solutions are increasingly a business

imperative, these systems are providing greater coverage area for each cell

site, higher rejection of interference, and substantial capacity improvements.


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Fig 3.1:- Smart Antenna System

Figure 3.2- Block Diagram ofSmart Antenna

3.2- History of Smart Antenna

Early smart antennas were designed for governmental use in military

applications, which used directed beams to hide transmissions from an

enemy. Implementation required very large antenna structures and time-

intensive processing and calculation.

As personal wireless communications began to emerge, it was evident that

interference in wireless networks was limiting the total number of

simultaneous users the network could handle before unacceptable call

quality and blocking occurred. Since the narrow beams of the early

governmental smart antennas created less overall interference, researchers

began to explore the possibility of extending the use of smart antennas to

reduce overall network interference in commercial wireless networks, thusincreasing the total number of users a wireless system could handle in a

given block of spectrum. But the hardware and processing technologies

required to perform the complex calculations in the very small spaces of

time available in personal wireless communications would prove to be a

hurdle that was extremely difficult to overcome. A few select companies have


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successfully developed and introduced smart antenna technologies into

commercial wireless networks.

Antennas were used in 1888 by Heinrich Hertz (1857-1894) to prove the

existence of electromagnetic waves predicted by the theory of James

Clerk Maxwell. Hertz placed the emitter dipole in the focal point of a

parabolic reflector.

The origin of the word antennarelative to wireless apparatus is attributed to

Guglielmo Marconi. In 1895, while testing early radio apparatus in the Swiss

Alps ,Marconi experimented with early wireless equipment.

A 2.5 meter long pole, along which was carried a wire, was used as a

radiating and receiving aerial element . Until then wireless radiating

transmitting and receiving elements were known simply as aerials or

terminals. Marconi's use of the word antenna(Italian forpole) would become

a popular term for what today is uniformly known as the antenna.

Smart Antennas Today

Today, smart antennas have been widely deployed in many of the top

wireless networks worldwide to address wireless network capacity and

performance challenges.

Several different versions of smart antennas are either in development or

available on the market today. Appliqu smart antenna systems can be

added to existing cell sites, enabling software-controlled pattern changes or

software-optimized antenna patterns that have produced capacity increases

of up to 35-94% in some deployments. Appliqu smart antenna systems

provide greater flexibility in controlling and customizing sector antenna

pattern beamwidth and azimuthal orientation over that of standard sector

antennas.


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A second approach, embedded smart antennas, uses adaptive array

processing within the channel elements of a base station. The smart

antenna processing takes place in the base station signal path, using a

custom, narrow beam to track each mobile in the network. Embedded smart

antenna system trials have been proven to deliver 2.5-3 times the capacity

of current 2-2.5G base stations.

3.3- Types of Smart Antenna

The following are distinctions between the two major categories of smart

antennas regarding the choices in transmit strategy:

1).Adaptive array - an infinite number of patterns (scenario-based) that are

adjusted in real time .

2).Switched beam - a finite number of fixed, predefined patterns or

combining strategies (sectors).

3.3.1- Adaptive Array

Adaptive antenna technology represents the most advanced smart antenna

approach to date. Using a variety of new signal-processing algorithms, the

adaptive system takes advantage of its ability to effectively locate and track

various types of signals to dynamically minimize interference and maximize

intended signal reception.

Both systems attempt to increase gain according to the location of the user;

however, only the adaptive system provides optimal gain while

simultaneously identifying, tracking, and minimizing interfering signals


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Both systems attempt to increase gain according to the location of the

ultaneously identifying, tracking, and minimizing interfering signals.

Figure 3.3:- Adaptive

Array System:-

Representative

Depiction of a Main Lobe Extending Toward a User.

3.3.2- Switched Beam

Switched beam antenna systems form multiple fixed beams with heightened

sensitivity in particular directions. These antenna systems detect signal

strength, choose from one of several predetermined, fixed beams, and switch

from one beam to another as the mobile moves throughout the sector.

Instead of shaping the directional antenna pattern with the metallic

properties and physical design of a single element (like a sectorized

antenna), switched beam systems combine the outputs of multiple antennas

in such a way as to form finely sectorized (directional) beams with more

spatial selectivity than can be achieved with conventional, single-element

approaches.

Figure 3.4:-Switched BeamSystem


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3.4- Relative Benefits of Switched Beam and

Adaptive Array Systems

Integration

Switched beam systems are traditionally designed to retrofit widely deployed

cellular systems. It has been commonly implemented as an add-on or

appliqu technology that intelligently addresses the needs of mature

networks

Range/coverage

Switched beam systems can increase base station range from 20 to 200

percent over conventional sectored cells, depending on environmental

circumstances and the hardware/software used. The added coverage can

save an operator substantial infrastructure costs and means lower prices for

consumers. Also, the dynamic switching from beam to beam conserves

capacity because the system does not send all signals in all directions. In

comparison, adaptive array systems can cover a broader, more uniform area

with the same power levels as a switched beam system.

Interferencesuppression

Switched beam antennas suppress interference arriving from directions

away from the active beam's center. Because beam patterns are fixed,

however, actual interference rejection is often the gain of the selected

communication beam pattern in the interferer's direction. Also, they are

normally used only for reception because of the system's ambiguous

perception of the location of the received signal (the consequences of

transmitting in the wrong beam being obvious). Also, because their beams

are predetermined, sensitivity can occasionally vary as the user moves

through the sector.

Adaptive array technology currently offers more comprehensive interference

rejection. Also, because it transmits an infinite, rather than finite, number


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of combinations, its narrower focus creates less interference to neighboring

users than a switched-beam approach.

3.5-Working of Smart Antenna

Traditional switched beam and adaptive array systems enable a base station

to customize the beams they generate for each remote user effectively by

means of internal feedback control. Generally speaking, each approach

forms a main lobe toward individual users and attempts to reject

interference or noise from outside of the main lobe.

Listening to the Cell (Uplink Processing)

It is assumed here that a smart antenna is only employed at the base

station and not at the handset or subscriber unit. Such remote radio

terminals transmit using omnidirectional antennas, leaving it to the base

station to separate the desired signals from interference selectively.

Typically, the received signal from the spatially distributed antenna

elements is multiplied by a weight, a complex adjustment of an amplitude

and a phase. These signals are combined to yield the array output. An

adaptive algorithm controls the weights according to predefined objectives.

For a switched beam system, this may be primarily maximum gain; for an

adaptive array system, other factors may receive equal consideration. These

dynamic calculations enable the system to change its radiation pattern for

optimized signal reception.

Speaking to the Users (Downlink Processing)

The task of transmitting in a spatially selective manner is the major basis

for differentiating between switched beam and adaptive array systems. As

described below, switched beam systems communicate with users by

changing between preset directional patterns, largely on the basis of signal

strength. In comparison, adaptive arrays attempt to understand the RF

environment more comprehensively and transmit more selectively.


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The type of downlink processing used depends on whether the

communication system uses time division duplex (TDD), which transmits

and receives on the same frequency (e.g., PHS and DECT) or frequency

division duplex (FDD), which uses separate frequencies for transmit and

receiving (e.g., GSM). In most FDD systems, the uplink and downlink fading

and other propagation characteristics

may be considered independent, whereas in TDD systems the uplink and

downlink channels can be considered reciprocal. Hence, in TDD systems

uplink channel information may be used to achieve spatially selective

transmission. In FDD systems, the uplink channel information cannot be

used directly and other types of downlink processing must be considered.

3.6- Categories of Smart Antenna

A smart antenna is a digital wireless communications antenna system that

takes advantage of diversity effect at the source (transmitter), the

destination (receiver), or both. Diversity effect involves the transmission

and/or reception of multiple radio frequency (RF) waves to increase data

speed and reduce the error rate.

In conventional wireless communications, a single antenna is used at thesource, and another single antenna is used at the destination. This is called

SISO (single input, single output). Such systems are vulnerable to problems

caused by multipath effects. When an electromagnetic field (EM field) is met

with obstructions such as hills, canyons, buildings, and utility wires, the

wavefronts are scattered, and thus they take many paths to reach the

destination. The late arrival of scattered portions of the signal causes

problems such as fading, cut-out (cliff effect), and intermittent reception

(picket fencing). In a digital communications system like the Internet, it can

cause a reduction in data speed and an increase in the number of errors.

The use of smart antennas can reduce or eliminate the trouble caused by

multipath wave propagation.

Smart antennas fall into three major categories:--


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1). SIMO (single input, multiple output)

2). MISO (multiple input, single output)

3). MIMO (multiple input, multiple output).

SIMO

SIMO (single input, multiple output) is an antenna technology for wireless

communications in which multiple antennas are used at the destination

(receiver). The antennas are combined to minimize errors and optimize data

speed. The source (transmitter) has only one antenna. SIMO is one of

several forms of smart antenna technology, the others being MIMO (multiple

input, multiple output) and MISO (multiple input, single output).

In digital communications systems such as wireless Internet, it can cause a

reduction in data speed and an increase in the number of errors. The use of

two or more antennas at the destination can reduce the trouble caused by

multipath wave propagation.

SIMO technology has widespread applications in digital television (DTV),

wireless local area networks (WLANs), metropolitan area networks (MANs),

and mobile communications. An early form of SIMO, known as diversity

reception, has been used by military, commercial, amateur, and shortwave

radio operators at frequencies below 30 MHz since the First World War.

MISO

MISO (multiple input, single output) is an antenna technology for wireless

communications in which multiple antennas are used at the source

(transmitter). The antennas are combined to minimize errors and optimize

data speed. The destination (receiver) has only one antenna. MISO is one of

several forms of smart antenna technology, the others being MIMO (multiple

input, multiple output) and SIMO (single input, multiple output).

In digital communications systems such as wireless Internet, it can cause a

reduction in data speed and an increase in the number of errors. The use of


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two or more antennas, along with the transmission of multiple signals (one

for each antenna) at the source, can reduce the trouble caused by multipath

wave propagation.

MISO

technology has widespread applications in digitaltelevision (DTV), wireless local area networks (WLANs), metropolitan area

networks (MANs), and mobile communications.

MIMO

MIMO (multiple input, multiple output) is an antenna

technology for wireless communications in which multiple antennas are

used at both the source (transmitter) and the destination (receiver). The

antennas at each end of the communications circuit are combined to

minimize errors and optimize data speed. MIMO is one of several forms of

smart antenna technology, the others being MISO (multiple input, single

output) and SIMO (single input, multiple output).

In digital communications systems such as wireless Internet, it

can cause a reduction in data speed and an increase in the number of

errors. The use of two or more antennas, along with the transmission of

multiple signals (one for each antenna) at the source and the destination,

eliminates the trouble caused by multipath wave propagation, and can even

take advantage of this effect.

MIMO technology has aroused interest because of its

possible applications in digital television (DTV), wireless local area networks

(WLANs), metropolitan area networks (MANs), and mobile communications.


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sometimes called a mic (pronounced mike), is a device that converts sound

into an electrical signal. In telecommunications, and particularly in radio,

signal strength is the measure of how strongly a transmitted signal is being

received, measured, or predicted, at a reference point that is a significant

distance from the transmitting antenna.

Beamforming takes advantage of interference to change the directionality of

the array. When transmitting, a beamformer controls the phase and relative

amplitude of the signal at each transmitter, in order to create a pattern of

constructive and destructive interference in the wavefront. When receiving,

information from different sensors iscombined in such a way that the

expected pattern of radiation is preferentially observed. Interference of two

circular waves - Wavelength (decreasing bottom to top) and Wave centers

distance (increasing to the right).

In the receive beamfomer the signal from each antenna may be amplified by

a different "weight." Different weighting patterns (eg Dolph-Chebyshev) can

be used to achieve the desired sensitivity patterns. . A main lobe is produced

together with nulls and sidelobes. As well as controlling the main lobe width

(the beam) and the sidelobe levels, the position of a null can be controlled.

Figure3.5:- BeamForming Lobe


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This is useful to ignore noise or jammers in one particular direction, whilelistening for events in other directions. A similar result can be obtained ontransmission. Jammer can refer to: A device used in electronic warfare toinhibit or halt the transmission of signals.

Figure3.6:- Figure show pattern ofBeamforming

Beamforming techniques can be broadly divided into two categories:

A).Conventional (fixed) beamformers or switched beam smart antennas.

B).Adaptive beamformers or adaptive array smart antennas

Conventional beamformers use a fixed set of weightings and time-delays (or

phasings) to combine the signals from the sensors in the array, primarily

using only information about the location of the sensors in space and the

wave directions of interest. In contrast, adaptive beamforming techniques,

generally combine this information with properties of the signals actually

received by the array, typically to improve rejection of unwanted signals

from other directions. This process may be carried out in the time or


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frequency domains. Smart Antenna refers to a system of antenna arrays

with smart signal processing algorithms that are used to identify the

direction of arrival (DOA) of the signal, and use it to calculate beamforming

vectors, to track and locate the antenna beam on the mobile/target. ...

Smart Antenna

refers to a system of antenna arrays with smart signal processing algorithms

that are used to identify the direction of arrival (DOA) of the signal, and use

it to calculate beamforming vectors, to track and locate the antenna beam

on the mobile/target. ...

As the name indicates, an adaptive beamformer is able to adapt

automatically its response to different situations. Some criterion has to be

set up to allow the adaption to proceed such as minimising the total noise

output. Because of the variation of noise with frequency, in wide band

systems it may be desirable to carry out the process in the frequency

domain. An adaptive beamformer is signal processing system often used

with an array of radar antennae (or phased array) in order to transmit orreceive signals in different directions without having to mechanically steer

the array. ... Frequency domain is a term used to describe the analysis of

mathematical functions with respect to frequency.

3.7.2- Direction of Arrival(DOA)

Direction of arrival(DOA) denotes the direction from which usually a

propagating wave arrives at a point, where usually a set of sensors are

located. This set of sensors forms what is called a sensor array. Often there

is the associated technique of beamforming which is estimating the signal

from a given direction. Various engineering problems addressed in the

associated literature are as follows: A wave crashing against the shore A

wave is a disturbance that propagates. Beamforming is the process of

delaying the outputs of the sensors in an arrays aperture and adding these


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together, to reinforce the signal with respect to noise or waves propagating

in different directions.

Find the direction relative to the array where the underwater sound

Source is located.

Direction of different sound sources around you are also located by you

using a process similar to those used by the algorithms in the literature.

Radio telescopes use these techniques to look at a certain location in the

sky.

Recently beamforming has also been used in RF applications such as

wireless communication. Compared with the spatial diversity techniques,

beamforming is preferred in terms of complexity. On the other hand

beamforming in general has much lower data rates.In multiple access

channel(CDMA,FDMA,TDMA) beamforming is necessary & sufficient.

The smart antenna system estimates the direction of arrival of the signal,

using any of the techniques like MUSIC (Multiple Signal Classification) or

ESPRIT (Estimation of Signal Parameters via Rotational Invariant

Techniques) algorithms,Matrix Pencil method or their derivatives. They

involve finding a spatial spectrum of the antenna/sensor array, and

calculating the DOA from the peaks of this spectrum. MUSIC involves

calculation of eigenvalues and eigenvectors of an autocorrelation matrix of

the input vectors from the receiving antenna array. These calculations are

computationally intensive. Matrix Pencil is very efficient in case of real time

systems, and under the correlated sources. In mathematics, a number is

called an eigenvalue of a matrix if there exists a nonzero vector such that

the matrix times the vector is equal to the same vector multiplied by the

eigenvalue.In linear algebra, the eigenvectors (from the German eigen


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meaning own) of a linear operator are non-zero vectors which, when

operated on by the operator, result in a scalar multiple of themselves.

3.8- Parameters affecting Antenna

performance

There are several critical parameters affecting an antenna's performance

that can be adjusted during the design process. These impedance are

resonant frequency, gain, aperture or radiation pattern, polarization,

efficiency and bandwidth. Transmit antennas may also have a maximum

power rating, and receive antennas differ in their noise rejection properties.

All of these parameters can be measuredthrough various means.

Resonant frequency

The "Resonant frequency and electrical resonance is related to the

electrical length of an antenna. The electrical length is usually the physical

length of the wire divided by its velocity factor (the ratio of the speed of wavepropagation in the wire to c0, the speed of light in a vacuum). Typically an

antenna is tuned for a specific frequency, and is effective for a range of

frequencies that are usually centered on that resonant frequency. However,

other properties of an antenna change with frequency, in particular the

radiation pattern and impedance, so the antenna's resonant frequency may

merely be close to the center frequency of these other more important

properties.

Antennas can be made resonant on harmonicfrequencies with lengths that

are fractions of the target wavelength. Some antenna designs have multiple

resonant frequencies, and some are relatively effective over a very broad

range of frequencies. The most commonly known type of wide band aerial is


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the logarithmic or log periodic, but its gain is usually much lower than that

of a specific or narrower band aerial.

Gain

Gain as a parameter measures the efficiency of a given antenna with respect

to a given norm, usually achieved by modification of its directionality. An

antenna with a low gain emits radiation with about the same power in all

directions, whereas a high-gain antenna will preferentially radiate in

particular directions. Specifically, the Gain, Directive gain or Power gain of

an antenna is defined as the ratio of the intensity (power per unit surface)

radiated by the antenna in a given direction at an arbitrary distance divided

by the intensity radiated at the same distance by a hypothetical isotropic

antenna.

The gain of an antenna is a passive phenomenon - power is not added by the

antenna, but simply redistributed to provide more radiated power in a

certain direction than would be transmitted by an isotropic antenna. If an

antenna has a gain greater than one in some directions, it must have a gain

less than one in other directions, since energy is conserved by the antenna.

An antenna designer must take into account the application for the antenna

when determining the gain. High-gain antennas have the advantage of

longer range and better signal quality, but must be aimed carefully in a

particular direction. Low-gain antennas have shorter range, but the

orientation of the antenna is relatively inconsequential. For example, a dish

antenna on a spacecraft is a high-gain device that must be pointed at the

planet to be effective, whereas a typical Wi-Fiantenna in a laptop computer

is low-gain, and as long as the base station is within range, the antenna can

be in any orientation in space. It makes sense to improve horizontal range at

the expense of reception above or below the antenna. Thus most antennas

labelled "omnidirectional" really have some gain.


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Radiation pattern

Theradiation pattern of an antenna is the geometric pattern of the relative

field strengths of the field emitted by the antenna. For the ideal isotropic

antenna, this would be asphere. For a typical dipole, this would be a toroid.

The radiation pattern of an antenna is typically represented by a three

dimensional graph, or polar plots of the horizontal and vertical cross

sections. The graph should show sidelobes and backlobes, where the

antenna's gain is at a minima or maxima.

Impedance

As an electro-magnetic wave travels through the different parts of the

antenna system (radio, feed line, antenna, free space) it may encounter

differences in impedance (E/H, V/I, etc). At each interface, depending on the

impedance match, some fraction of the wave's energy will reflect back to thesource[5], forming a standing wave in the feed line. The ratio of maximum

power to minimum power in the wave can be measured and is called the

standing wave ratio (SWR). A SWR of 1:1 is ideal. A SWR of 1.5:1 is

considered to be marginally acceptable in low power applications where

power loss is more critical, although an SWR as high as 6:1 may still be

usable with the right equipment. Minimizing impedance differences at each

interface (impedance matching) will reduce SWR and maximize power

transfer through each part of the antenna system.

Complex impedance of an antenna is related to the electrical length of the

antenna at the wavelength in use. The impedance of an antenna can be

matched to the feed line and radio by adjusting the impedance of the feed

line, using the feed line as an impedance transformer.


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More commonly, the impedance is adjusted at the load (see below) with an

antenna tuner, a balun , a matching transformer, matching networks

composed of inductors and capacitors, or matching sections such as the

gamma match.

Efficiency

Efficiency is the ratio of power actually radiated to the power put into the

antenna terminals. A dummy loadmay have an SWR of 1:1 but an efficiency

of 0, as it absorbs all power and radiates heat but not RF energy, showing

that SWR alone is not an effective measure of an antenna's efficiency.

Radiation in an antenna is caused by radiation resistancewhich can only

be measured as part of total resistance including loss resistance. Loss

resistance usually results in heat generation rather than radiation, and

reduces efficiency. Mathematically, efficiency is calculated as radiation

resistance divided by total resistance.

Bandwidth

The bandwidth of an antenna is the range of frequencies over which it is

effective, usually centered on the resonant frequency. The bandwidth of an

antenna may be increased by several techniques, including using thicker

wires, replacing wires with cages to simulate a thicker wire, tapering

antenna components (like in afeed horn), and combining multiple antennas

into a single assembly and allowing the natural impedance to select the

correct antenna. Small antennas are usually preferred for convenience, but

there is a fundamental limit relating bandwidth, size and efficiency.


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Polarization

Thepolarizationof an antenna is the orientation of the electric field (E-plane)

of the radio wave with respect to the Earth's surface and is determined by

the physical structure of the antenna and by its orientation. It has nothing

in common with antenna directionality terms: "horizontal", "vertical" and

"circular". Thus, a simple straight wire antenna will have one polarization

when mounted vertically, and a different polarization when mounted

horizontally. "Electromagnetic wave polarization filters" are structures whichcan be employed to act directly on the electromagnetic wave to filter out

wave energy of an undesired polarization and to pass wave energy of a

desired polarization.

Reflections generally affect polarization. For radio waves the most important

reflector is the ionosphere - signals which reflect from it will have their

polarization changed unpredictably. For signals which are reflected by the

ionosphere, polarization cannot be relied upon. For line of sightcommunications for which polarization can be relied upon, it can make a

large difference in signal quality to have the transmitter and receiver using

the same polarization; many tens of dB difference are commonly seen and

this is more than enough to make the difference between reasonable

communication and a broken link.

Polarization is largely predictable from antenna construction but, especially

in directional antennas, the polarization of side lobes can be quite different

from that of the main propagation lobe. For radio antennas, polarization

corresponds to the orientation of the radiating element in an antenna. A

vertical omnidirectional Wi-Fi antenna will have vertical polarization (the

most common type). An exception is a class of elongated waveguide

antennas in which vertically placed antennas are horizontally polarized.


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Many commercial antennas are marked as to the polarization of their

emitted signals.

Polarization is the sum of the E-plane orientations over time projected onto

an imaginary plane perpendicular to the direction of motion of the radiowave. In the most general case, polarization is elliptical (the projection is

oblong), meaning that the antenna varies over time in the polarization of the

radio waves it is emitting. Two special cases are linear polarization (the

ellipse collapses into a line) and circular polarization (in which the ellipse

varies maximally). In linear polarization the antenna compels the electric

field of the emitted radio wave to a particular orientation. Depending on the

orientation of the antenna mounting, the usual linear cases are horizontal

and vertical polarization. In circular polarization, the antenna continuously

varies the electric field of the radio wave through all possible values of its

orientation with regard to the Earth's surface. Circular polarizations, like

elliptical ones, are classified as right-hand polarized or left-hand polarized

using a "thumb in the direction of the propagation" rule. Optical researchers

use the same rule of thumb, but pointing it in the direction of the emitter,

not in the direction of propagation, and so are opposite to radio engineers'

use.

In practice, regardless of confusing terminology, it is important that linearly

polarized antennas be matched, lest the received signal strength be greatly

reduced. So horizontal should be used with horizontal and vertical with

vertical. Intermediate matchings will lose some signal strength, but not as

much as a complete mismatch. Transmitters mounted on vehicles with large

motional freedom commonly use circularly polarized antennas so that there

will never be a complete mismatch with signals from other sources. In the

case of radar, this is often reflections from rain drops.


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Transmission and reception

All of the antenna parameters are expressed in terms of a transmission

antenna, but are identically applicable to a receiving antenna, due to

reciprocity. Impedance, however, is not applied in an obvious way; for

impedance, the impedance at the load (where the power is consumed) is

most critical. For a transmitting antenna, this is the antenna itself. For a

receiving antenna, this is at the (radio) receiver rather than at the antenna.

Tuning is done by adjusting the length of an electrically long linear antenna

to alter the electrical resonance of the antenna.

Antenna tuning is done by adjusting an inductance or capacitance

combined with the active antenna (but distinct and separate from the active

antenna). The inductance or capacitance provides the reactance which

combines with the inherent reactance of the active antenna to establish a

resonance in a circuit including the active antenna. The established

resonance being at a frequency other than the natural electrical resonant

frequency of the active antenna. Adjustment of the inductance or

capacitance changes this resonance.

Antennas used for transmission have a maximum power rating, beyond

which heating, arcing or sparking may occur in the components, which may

cause them to be damaged or destroyed. Raising this maximum power rating

usually requires larger and heavier components, which may require larger

and heavier supporting structures. This is a concern only for transmitting

antennas, as the power received by an antenna rarely exceeds the microwatt

range.

Antennas designed specifically for reception might be optimized for

noise rejection capabilities. An antenna shield is a conductive or low

reluctance structure (such as a wire, plate or grid) which is adapted to be

placed in the vicinity of an antenna to reduce, as by dissipation through a

resistance or by conduction to ground, undesired electromagnetic radiation,


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a.

or electric or magnetic fields, which are directed toward the active antenna

from an external source or which emanate from the active antenna. Other

methods to optimize for noise rejection can be done by selecting a narrow

bandwidth so that noise from other frequencies is rejected, or selecting a

specific radiation pattern to reject noise from a specific direction, or by

selecting a polarization different from the noise polarization, or by selecting

an antenna that favors either the electric or magnetic field.

For instance, an antenna to be used for reception of low frequencies (below

about ten megahertz) will be subject to both man-made noise from motors

and other machinery, and from natural sources such as lightning.

Successfully rejecting these forms of noise is an important antenna feature.

A small coil of wire with many turns is more able to reject such noise than a

vertical antenna. However, the vertical will radiate much more effectively on

transmit, where extraneous signals are not a concern.

3.9- Application of Smart Antenna

Smart Antenna is used in number of fields. It has number of Applications.

Here are some of the fields where Smart Antenna used:-

1). MOBILE COMMUNICAION.

2).WIRELESS COMMUNICATION.

3). RADAR.

4).SONAR

APPLICATION OF SMART ANTENNAS TO MOBILECOMMUNICATIONS SYSTEMS

Smart or adaptive antenna arrays can improve the performance of wireless

communication systems. An overview of strategies for achieving coverage,

capacity, and other improvements is presented, and relevant literature is


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discussed. Multipath mitigation and direction finding applications of arrays

are briefly discussed, and potential paths of evolution for future wireless

systems are presented. Requirements and implementation issues for smart

antennas are also considered.

Smart antennas are most often realized with either switched-beam or fully

adaptive array antennas. An array consists of two or more antennas (the

elements of the array) spatially arranged and electrically interconnected to

produce a directional radiation pattern. In a phased array the phases of the

exciting currents in each element antenna of the array are adjusted to

change the pattern of the array, typically to scan a pattern maximum or null

to a desired direction.

A smart antenna system consists of an antenna array, associated RF

hardware, and a computer controller that changes the array pattern in

response to the radio frequency environment, in order to improve the

performance of a communication or radar system.

Switched-beam antenna systems are the simplest form of smart antenna. By

selecting among several different fixed phase shifts in the array feed, several

fixed antenna patterns can be formed using the same array. The appropriate

pattern is selected for any given set of conditions. An adaptive array controlsits own pattern dynamically, using feedback to vary the phase and/or

amplitude of the exciting current at each element to optimize the received

signal.

Smart or adaptive antennas are being considered for use in wireless

communication systems. Smart antennas can increase the coverage and

capacity of a system. In multipath channels they can increase the maximum

data rate and mitigate fading due to cancellation of multipath components.

Adaptive antennas can also be used for direction finding, with applications

including emergency services and vehicular traffic

monitoring. All these enhancements have been proposed in the literature

and are discussed in this paper. In addition, possible paths of evolution,

incorporating adaptive antennas into North American cellular systems, are


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presented and discussed. Finally, requirements for future adaptive antenna

systems and implementation issues that will

influence their design are outlined.

Range extension

In sparsely populated areas, extending coverage is often more important

than increasing capacity. In such areas, the gain provided by adaptive

antennas can extend the range of a cell to cover a larger area and more

users than would be possible with omnidirectional or sector antennas.

Interference reduction and rejection

In populated areas, increasing capacity is of prime importance. Two related

strategies for increasing capacity are interference reduction on the downlink

and interference rejection on the uplink. To reduce interference, directional

beams are steered toward the mobiles. Interference to co-channel mobiles

occurs only if they are within the narrow beamwidth of the directional beam.

This reduces the probability of co-channel interference compared with a

system using omnidirectional base station antennas.

Interference can be rejected using directional beams and/or by forming

nulls in the base station receive antenna pattern in the direction of

interfering co-channel users.

Interference reduction and rejection can allow N c (which is dictated by co-

channel interference) to be reduced, increasing the capacity of the system.

Interference reduction can be implemented using an array with steered or

switched beams. By using directional beams to communicate with mobiles

on the downlink, a base station is less likely to interfere with nearby co-

channel base stations than if it used an omnidirectional antenna.

There will be a small percentage of time during which co-channel

interference is strong, e.g., when a mobile is within the main beam of a

nearby co-channel base station.


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This can be overcome by handing off the mobile within its current cell to

another channel that is not experiencing strong co-channel interference.

3.10- Advantages and Disadvantages of

Smart Antenna

Advantages

Increased number of users

Due to the targeted nature of smart antennas frequencies can be reusedallowing an increased number of users. More users on the same frequency

space means that the network provider has lower operating costs in terms of

purchasing frequency space.

Increased Range

As the smart antenna focuses gain on the communicating device, the range

of operation increases. This allows the area serviced by a smart antenna to

increase. This can provide a cost saving to network providers as they will not

require as many antennas/base stations to provide coverage.

Geographic Information

As smart antennas use targeted signals the direction in which the antenna

is transmitting and the gain required to communicate with a device can be

used to determine the location of a device relatively accurately. This allows

network providers to offer new services to devices. Some services include,

guiding emergency services to your location, location based games and

locality information.


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Security

Smart antennas naturally provide increased security, as the signals are not

radiated in all directions as in a traditional omni-directional antenna. This

means that if someone wished to intercept transmissions they would need tobe at the same location or between the two communicating devices.

Reduced Interference

Interference which is usually caused by transmissions which radiate in all

directions are less likely to occur due to the directionality introduced by the

smart antenna. This aids both the ability to reuse frequencies and achieve

greater range.

Increased bandwidth

The bandwidth available increases form the reuse of frequencies and also in

adaptive arrays as they can utilize the many paths which a signal may

follow to reach a device.

Easily integrated

Smart antennas are not a new protocol or standard so the antennas can be

easily implemented with existing non smart antennas and devices.

Disadvantages

Complex

A disadvantage of smart antennas is that they are far more complicated

than traditional antennas. This means that faults or problems may be

harder to diagnose and more likely to occur.

More Expensive

As smart antennas are extremely complex, utilizing the latest in processing

technology they are far more expensive than traditional antennas. However

this cost must be weighed against the cost of frequency space.


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Larger Size

Due to the antenna arrays which are utilized by smart antenna systems,

they are much larger in size than traditional systems. This can be a

problem in a social context as antennas can be seen as ugly or unsightly.

Location

The location of smart antennas needs to be considered for optimal

operation. Due to the directional beam that swings from a smart antenna

locations which are optimal for a traditional antenna are not for a smart

antenna. For example in a road context, smart antennas are better situated

away from the road, unlike normal antennas which are best situated along

the road.

3.11- Features and Benefit of Smart Antenna

Feature of Smart Antenna

1).Signal gain - Inputs from multiple antennas are combined to optimize

available power required to establish given level of coverage.

2).Interference Rejection - Antenna pattern can be generated toward

cochannel interference sources, improving the signal-to-interference ratio of

the received signals.

3).Spatial diversity-Composite information from the array is used to

minimize fading and other undesirable effects of multipath propagation.

4).Power efficiency- Combines the inputs to multiple elements to optimize

available processing gain in the downlink (toward the user)


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Benefit of Smart Antenna

1).Better range/coverage- Focusing the energy sent out into the cell

increases base station range and coverage. Lower power requirements also

enable a greater battery life and smaller/lighter handset size.

2).Increased capacity- Precise control of signal nulls quality and mitigationof interference combine to frequency reuse reduce distance (or cluster size),

improving capacity. Certain adaptive technologies (such as space division

multiple access) support the reuse of frequencies within the same cell.

3).Multipath rejection- Can reduce the effective delay spread of the

channel, allowing higher bit rates to be supported without the use of an

equalizer.

4).Reduced expense- Lower amplifier costs, power consumption, and higher

reliability will result.


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Conclusion

This project has discussed about the history and working

performance of Smart Antenna. This project summarized different types and

functions of Smart Antenna and design of possible arrangements of Smart

Antenna. Here, also we discussed about advantages and disadvantages of

Smart antenna also. Here, we can get so many examples and applications of

Smart Antenna.

In this project, it will help us to understand about Smart

Antenna clearly with different structures, Adaptive array antennas play

important role in the evolution of wireless communication system and

Mobile communication systems. In Beamforming antenna system improve

the wireless network performance, increases system capacity and save

power, improve signal quality, suppress interference and noise.


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a.

References

1).www.wikipedia.com

2).www.statemaster.com

3).www.iec.org

4).http://www.iec.org/online/tutorials/smart_ant/

5).W. L. Stutzman and G. A. Thiele, Antenna theory and Design,

JohnWiley & Sons, New York, 1981.

6). D. Johnson and D. Dudgeon, Array Signal Processing,

Prentice-

Hall, Englewood Cli_s, NJ, 1993

7). http://www.smartanteenas.googlepages.com

8). Michael Chryssomallis Smart antennas IEEE antenna and

propagat

ion

m

agazine

Vol 42 No 3 pp 129-138, June 2000.9). D. Johnson and D. Dudgeon, Array Signal Processing,

Prentice-

Hall, Englewood Cli_s, NJ, 1993

10). Special issue on blind identi_cation and estimation," IEEE

Proceedings, mid-1998 .

11). R Kronberger,H Lindermerier,J Hopf Smart antenna

applications on vehicles with low profile array antenna Proc

IEEEVol 53 pp1-3 September 2003.

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