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Basics of Antenna

Shunmugapriyan.MII Year M.E(Communication Systems)

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Outline

Antenna

Antenna Classification

Antenna Characteristics

RF tools

Antenna Design

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Antenna

An antenna is an electrical device which

converts electrical power into radio waves, and

vice versa.

The antenna radiates the energy from the

current electromagnetic waves(radio waves).

In reception an antenna converts

electromagnetic wave into a tiny voltage at its

terminals, that is applied to a amplifier.

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Wave Propagation in Antenna

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Antenna Classifications

Omni Directional

Monopole/Whip

Dipole

Loop

Whip

PIFA( Planar Inverted-F antenna) Bi-Conical

Directional Patch

YagiUda

Horn Helical

Parabolic

Log Periodic

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Characteristics of Antenna

Resonance Frequency

Return Loss

VSWR

Radiation Pattern

Directivity

Bandwidth

Beam Width

SAR-Specific Absorption Rate

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Resonance FrequencyFrequencies at which the response amplitude is

a relative maximum are known as the system's

resonant frequencies.

Resonance occurs when a system is able to

store and easily transfer energy between two

or more different storage modes.

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Return LossReturn loss is ratio between incident power

and reflected power.

= 10

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VSWR

VSWR=

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Relation between VSWR, Reflection

Coefficient and Return lossVSWR Refection

Coefficient()

Reflected

Power(%)

Reflected

Power(dB)

1 0.000 0.000 -infinity

1.5 0.200 4 -14

2 0.333 11.1 -9.55

2.5 0.429 18.4 -7.36

3 0.5 25 -6

6 0.714 51 -2.92

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Radiation Pattern

Graphical representation of received power by

an antenna.

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Directivity

antenna radiates in the direction of its strongest

emission, versus the power density radiated by

an ideal isotropic radiator.

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Bandwidth

Bandwidth is difference between upper cut off

frequency and lower cut off frequency.

Bandwidth(Hz)=

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SAR

Specific absorption rate (SAR) is a measure

of the rate at which energy is absorbed by the

body when exposed to a radio frequency (RF)

electromagnetic field.

It can also refer to absorption of other forms of

energy by tissue, including ultrasound.

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Mobile Phone SAR

Brand SAR(W/Kg)

SAMSUNG 0.29-0.96

NOKIA 0.8-1.3

SONY ERICSSON 1.22-1.56

MOTOROLA 0.45-1.52

LG 0.35-1.52

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RF Tools

2D Tools

Agilent Advanced Design System (ADS)

Empire Xccel

3D Tools HFSS

CST Studio Suite

IE3D

COMSOL

FEKO

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Antenna Design

Dielectric constant(FR4=4.4-4.6)

Substrate Height(1.6mm)

Application

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Return Loss

Return loss is -22.71dB

at the Resonance

frequency of 2.4GHz

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VSWR

VSWR is 1.16 at the

Resonance frequency

of 2.4GHz

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Radiation Pattern

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