Lecture on pifa a ntenna1

Presented By :

Akhilesh Verma

NITTTR, Chandigarh

Outline

Introduction

o What is antenna

o How antennas work

o Need of antenna

o Use of antenna

o Parameters of antenna

Types of antenna use in mobile phone

o External antenna

o Internal antenna

Antennas use in different cell phones

Handset Design Evolution

1 June 2014 National Institute of Technical Teacher's Training & Research, Chandigarh

2

What is an antenna

An Antenna is a device used to transform an RF signal, travelling on a

conductor into an EM wave in free space or vice versa.

or

o An antenna is a transducer between a guided wave and a radiated wave, or

vice versa.

The structure that “guides” the energy to the antenna is most evident as a

coaxial cable attached to the antenna. The radiated energy is characterized

by the antenna’s radiation pattern.


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Continued…

Antennas demonstrate a property known as reciprocity , which means that

an antenna will maintain the same characteristic regardless if it is

transmitting or receiving.

Antennas can be broadcast or receive only.

A special license is needed to broadcast but not to receive.


4

How antennas work?

First of all to work properly the antenna system must be matched to the

transmitter.

All modern transmitter have an output impedance of 50Ω.

There are several ways to match them:

o Pruning the length of the antenna

o Using an antenna tuner

o Matching the antenna with the length of transmission line called a

matching section.

To understand the working of antenna, firstly you have to understand

electromagnetism.


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Continued…

If two poles of direct current(DC) voltage source to the two ends of a

coil of wire, current will flow through the coil of wire and it will

become magnetized. The magnetized coil is known as electromagnet.

If voltage and current can cause a coil to become magnetized, the

reverse is true i.e a magnetic field can produce a voltage and a current

in a coil, this is known as faradays principle of magnetic induction.

A voltage will produced at the ends of the coil of wire as we move any

permanent magnet close to and parallel to the coil.

Move the magnet in one direction, and current will flow in one

direction, reverse the direction the magnet is moving and the current

will flow in the opposite direction.


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Continued…

Moving the magnet back and forth produces alternating current.

Any moving magnetic field can induce current in another coil, if that

moving magnetic field passes through a second nearby coil, it will induce an

alternating current in the second coil.

A straight wire that has an AC current flowing through it also has a

magnetic field surrounding it. The magnetic field from the wire radiate out

into and become weaker with distance.

The radiating magnetic field from a wire is known as “electromagnetic

radiation”, the wire that radiates becomes the transmitting antenna.

Some distance away, a second wire in the path of these waves has current

induced into it by the passing electromagnetic waves. This second wire will

be the receiving antenna. 1 June 2014 National Institute of Technical Teacher's Training & Research, Chandigarh

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Need of antenna

For transmission

For reception

1 June 2014 National Institute of Technical Teacher's Training & Research, Chandigarh 8

Uses of antennas

Antennas are used for:

o Radio

o TV

o Satellite

o Cellular

o Wifi

o Radar

o Space communications


Parameters of antenna

1. Input impedance

2. Return loss

3. Bandwidth

4. Directivity

5. Gain

6. Radiation pattern

7. Beamwidth

8. Side lobes

9. Nulls

10. Polarization

National Institute of Technical Teacher's Training & Research, Chandigarh 10

Continued…

1. Input impedance

o For an efficient transfer of energy, the impedance of the radio, of the

antenna and of the transmission cable connecting them must be the same.

o Transceivers and their transmission lines are typically designed for 50Ω

impedance.

o If the antenna has an impedance different from 50Ω, then

there is a mismatch and an impedance matching circuit is required.

2. Return loss

o The return loss is another way of expressing mismatch.

o It is a logarithmic ratio measured in dB that compares the power reflected

by the antenna the power that is fed into the antenna from the transmission

line.


Continued…


Continued… 4. Directivity

o Directivity is the ability of an antenna to focus energy in a particular

direction when transmitting, or to receive energy better from a particular

direction when receiving.

o In a static situation, it is possible to use the antenna directivity to

concentrate the radiation beam in the wanted direction.

o In a dynamic system where the transceiver is not fixed, the antenna should

radiate equally in all directions, and this is known as an omni-directional

antenna.

5. Gain

o The gain of an antenna (in any given direction) is defined as the ratio of

the power gain in a given direction to the power gain of a reference

antenna in the same direction.


Continued…

o isotropic radiator as the reference antenna in this definition.

o isotropic radiator would be lossless and that it would radiate its energy

equally in all directions.

o An antenna gain of 3 dB compared to an isotropic antenna would be

written as 3 dBi.

6. Radiation pattern

o The radiation or antenna pattern describes the relative strength of the

radiated field in various directions from the antenna, at a constant

distance.


Continued…


Continued…

Dipole Antenna 3D radiation pattern Omni-Directional 3D pattern


Continued…

7. Beamwidth

o The angular distance between the half power points is defined as the

beamwidth.

o Half the power expressed in decibels is —3dB, so the half power

beamwidth is sometimes referred to as the 3dB.


Continued…

8. Side lobes

o No antenna is able to radiate all the energy in one preferred direction.

Some is inevitably radiated in other directions. The peaks are referred to as

side lobes, commonly specified in dB down from the main lobe.


Continued…

9. Nulls

o In an antenna radiation pattern, a null is a zone in which the effective

radiated power is at a minimum.

o A null often has a narrow directivity angle compared to that of the main

beam.

10. Polarization

o Polarization is defined as the orientation of the electric field of an

electromagnetic wave.

o Polarization is in general described by an ellipse.

o Two special cases of elliptical polarization are linear polarization

and circular polarization.


Continued… o With linear polarization the electric field vector stays in the same plane

all the time.

o Vertically polarized radiation is somewhat less affected by

reflections over the transmission path.

o Omnidirectional antennas always have vertical polarization.

o With horizontal polarization, such reflections cause variations in received

signal strength.

o In circular polarization the electric field vector appears to be rotating

with circular motion about the direction of propagation, making one

full turn for each RF cycle.


Continued…


Antennas for Mobile devices • The type of antenna that is used with a particular type of phone is normally

determined by dimensional considerations and specific absorption rate (SAR)

regulations.

• SAR(specific absorption rate) is a measurement of how much electromagnetic radiation

is absorbed by body tissue while using a mobile phone. Higher the SAR more radiation

will absorbed.

• In the United States, the Cellular Telecommunications and Internet Association

(CTIA) requires all cell phones to comply with the Federal Communications

Commission (FCC) SAR limit of 1.6 W/kg in 1g of tissue.


Data Sheet of SAR Values for Diff.

Mobile Phones

http://www.s21.com/sar.htm


Manufacturer Model SAR (W/Kg)

Apple iPhone 3G S 1.19

Apple iPhone 5 1.25

BlackBerry Curve 8900 1.01

BlackBerry Curve 9320 1.56

Samsung Chat S3350 0.817

Samsung Galaxy Nexus 0.456

Motorola A830 0.69

Motorola Z3 1.02

Nokia 2100 0.55

Nokia N97 0.66

Sony Xperia Z Ultra 0.339

Bad Effect of Cellphone on Health Impaired Concentration

o Excess use of mobile phones reduces your ability to focus.

o You take more time to do a task whether it’s solving

mathematical question or approaching the car breaks to avoid

an accident.

General Sickness

o The moment you touch the mobile screen , 20% to 30% of all

Virus and bacteria were transmitted to your hands and finally

into your body.


Bad Effect of Cellphone on Health Eye problems

o The combination of holding your phone too close to your

Eyes along with staring at its viciously small font can lead

to eye strain, headaches, dry eye and blurred vision.

Risk to Unborn

o Use of Cellphones during pregnancy slows down the rate of

brain development of the fetus or may lead to hyper activity.


Bad Effect of Cellphone on Health Neurodegenerative Disorders

o The harmful radiations emitted by the cell phones can

damage DNA

o DNA damage in brain cells can affect neurological functions

o This can possibly lead to neurodegenerative diseases

Heart risks

o Radiations from cordless phones (including mobile phones)

can cause irregularities in normal functioning of heart


Bad Effect of Cellphone on Health Loss of Hearing

o The radiation emitted by cell phones can damage delicate workings

of the inner ear

o People who are subjected to long-term mobile phone use are

at a higher risk of developing hearing loss

Brain Cancer

o Cell phone radiation may be slowly damaging your brain

o radio frequency field generated by your cell phone triggers heating

up of brain tissue


How to reduce your exposure to

phone radiation o Do not use your phone more than necessary and keep your calls short.

o Send a text instead of making a call.

o Try to avoid using your phone if the signal strength is low - find a better location to

make a call.

o Try to use the phone outdoors rather than inside, or move close to a window to

make a call.

o Keep the phone (and particularly the aerial) as far as possible from your head.

o Switch off your phone when not in use.

http://www.s21.com/sar.htm


Antennas for Mobile devices Following are main types of antennas used in cellular phones:

External Antennas

• Monopoles

• Helical


Continued… Following are main types of antennas used in cellular phones:

Internal Antennas

Microstrip antennas(MSA)

Planar inverted F antennas(PIFA)

Menader line antennas(MLA)


Planar inverted F antenna

The inverted F Antenna (IFA) typically consists of a rectangular planar element located

above a ground plane, a short circuiting plate or pin, and a feeding mechanism for the

planar element.

The inverted F antenna is a variant of the monopole where the top section has been

folded down so as to be parallel with the ground plane.

This is done to reduce the height of the antenna, while maintaining a resonant training

length.

PIFA can be considered as a kind of linear inverted F antenna (IFA) with the wire

radiator element replaced by a plate to expand the bandwidth.


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Continued…

Advantages of PIFA Antenna

o It can be hiding into the housing of the mobile while comparable to whip/rod/helix

antennas.

o It reduces the backward radiation toward the user’s head, minimizing specific absorption

rate (SAR).

Disadvantage of PIFA Antenna

o Narrow bandwidth characteristic of PIFA is one of the limitations for its commercial

application for wireless mobile.


Antennas use in different cell phones


Model Antenna Frequency bands

Apple iPhone 2G Planar Monopole GSM850/900/1800/1900

Apple iPhone 3G Planar Monopole GSM850/900/1800/1900+3G

Blackberry 8100 Planar Monopole GSM850/900/1800/1900

Motorola E398 PIFA GSM900/1800/1900

Motorola L2000/P7389 Helix GSM900/1800/1900

Motorola W208 PIFA GSM900/1800

Nokia 2626 PIFA

GSM900/1800

Nokia 2652 PIFA GSM900/1800

Sony Ericsson K660i PIFA GSM850/900/1800/1900+3G

Nokia 5300 Planar Monopole GSM900/1800/1900

Nokia 6210 PIFA GSM900/1800

Samsung SGH-2200

Helix GSM900/1800

Handset Design Evolution


1 June 2014 Cell Phone Antennas 35

The first DynaTAC

phone weighted

around 2.2 Kgs (approx.)

The battery life would

last for only 20 minutes

Nicknamed the

‘The BRICK’

Its cost was around

4,000 US Dollars

Quick Facts About the First Cell

Phone

How the handset antennas get evolved in the past 20 years?


1G(Analog) in 1980s-800 MHz


2G(Digital) in 1990s-GSM900 MHz

And 1800 MHz

New services came-text messaging, multimedia, internet access ,etc operated at GSM 900

MHz, later introduced at 1800 MHz


Continued…


Dual Band Internal Antenna


Single Band PIFA


First Dual Band PIFA


First 2G Mobile with Fully Internal

Antenna



First Triple Band PIFA


Handset Antennas in 2000s-3G 0


Location of antennas in different

mobile phones


Continued…


6/1/2014 Intrusion Detection Systems 49

Lecture on pifa a ntenna1

Documents

antenna tuner o

antenna directivity

transmitting antenna

receiving antenna

antenna system

working of antenna

loss o

o transceivers