FRACTAL ANTENNAS –A NOVEL

MINIATURIZATION TECHNIQUE

FOR WIRELESS COMMUNICATIONS

Prepared By : Patel Jay C

ME(EC)-140870705004

OBJECTIVE

To provide a study of different fractal antenna with an overview of recent

developments.

FRACTAL ANTENNA – AN INTRODUCTION

Fractal antenna theory – a new area

“fractal ” means broken or irregular fragments

“Family of complex shapes that possess an inherent self similarity or self

affinity in their geometrical structure”

Came from unique occurances in nature

FRACTAL ANTENNA

FRACTAL ANTENNA

Suggests some attractive solutions for using single small antenna needed

for different frequency bands (multiband operation)

Size, area and mass reduction (miniaturization)

The effective length of the antenna can be increased keeping the total area

same

GEOMETRY OF FRACTALS

The shape can be formed by iterative mathematical process called IFS

Based on series of affine transformations

w(x,y) = (ax+by+e, cx+dy+f)

○ a,b,c,d control rotation and scaling

○ e , f control linear translation

Repeatedly applying W to the previous geometryfractal geometry

A1=W(A0); A2 = W (A1);……..

GEOMETRY OF FRACTALS

IFS generated a sequence that converges to a final image

More no. of iterations increase in effective length decrease in resonant

frequency

Fractal geometry used in most of the works:

Koch fractal

Sirepinski fractal

Koch island fractal

A three iteration Sirepinski fractal

A FOUR ITERATION KOCH FRACTAL

A THREE ITERATION KOCH ISLAND

HOW MINIATURIZATION ?

Achieving lower fr with reduced length is miniaturization.

Fractal geometry comprise larger antenna length in a smaller

volume.

HOW MULTIBAND OPERATION?

A single antenna operating in two

or more freuquency bands

multiband operation

Antenna elements operating in

different frequency used

In fractal antenna coupling

between sharp angles produce

different current paths achieving

multi band operation

FRACTAL LOOP ANTENNAS

Loop antenna needs more space

Small loop

low input resistance-

mismatch to the transmission

line

KOCH LOOP

•A koch loop can be used loop antenna

•Perimeter gets increased maintaining the same volume

• less volume required for resonance

• input impedance improved

SIREPINSKI MONOPOLE AND DIPOLE

Multiple bands controlled by scale factors

Flare angle controls the frequency shift

Models developed to predict the performance

FRACTAL ANTENNA ARRAY

Antenna array : to improve the gain

Random fractal used to generate array configuration between periodic and

random

Low side lobe (feature of periodic array )

Robust (feature of random array)

four stage linear Cantor array

CONCLUSION

An overview of fractal antenna theory was presented.

Small sized, lo profile and low weight antennas can be developed by using

fractal geometries.

Being in early stage of development more innovations to come in the

future.

What is GPS ?

A very precise positioning system

• Developed and maintained by the US Department of Defense

(DOD)

• Satellite Based

* 24 satellites* 20,200 km high orbit

BUT!

Although it is a very precise geographic positioning system

•It is very easy to get youself into trouble

•Why?

•Because you (probably) don’t understand how it works

•And that leads to garbage

Characteristics of GPS

• Free

• Precise

• Reliable

• Anytime & anywhere

• All weather

• Unlimited user capacity

Almost!

Segments of GPS

1. Space Segment

A constellation of 24 satellites

2. Monitor StationA network of earth-based facilities

3. Users & Equipment

Source:Trimble

Segments of GPS

1. Space Segment

A constellation of 24 satellites

GPS Monitoring Station

How GPS Works ………

Uses measurements from 4+ satellites

Distance = travel time x speed of light

Source:Trimble

Determining GPS Position

• Suppose the distance fromSatellite A to our position is 11,000miles

• At this point we could be locatedanywhere on the specified sphere

Satellite A+

• Next, let us take another measurementfrom a second satellite, Satellite BSatellite B

+

• Now our position is narrowed down to the

intersection of theses two sphere

Satellite C+

Determining GPS Position

Satellite A

Satellite B+

+• Taking another measurement from

a 3rd satellite narrows our position down even further, to the two points

• So by ranging from 3 satellites we can narrow our position to just two points in space

• These points are located where the 3rd

sphere cuts through the the intersection of first two spheres

Satellite C+

How do we decide which one is our true location?

Satellite A

Satellite B+

+• We could make a 4th measurement

from another satellite to determine the true point

• However, GPS receivers use a 4th satellite to precisely locate our position

• We can eliminate one of the two points that gives a ridiculous answer

• The ridiculous point may be too far from the earth

OR

Determining GPS Position

How accurate is GPS?

Depends on some variables

• Design of receiver

• Relative positions of satellites, technically known as PDOP (Position

dilution of precision)

• Postprocessing

• Time spent on measurement

GPS Receivers

GeoXT Versus Garmin

Mostly used for GIS data collection

Mostly used for recreational purposes

How accurate is GPS?

Depends on some variables

• Design of receiver

• Relative positions of satellites, often known as DOP (Dilution of

Precision)

• Postprocessing

• Time spent on measurement

WAAS

• Wide Area Augmentation System.

• It provides FREE GPS differential correction data for visible satellites.

• Developed & operated by the FAA (Federal Aviation Administration) for flight

navigation but it’s available free to GPS users.

• WAAS-enabled receivers can provide sub-meter level accuracy anywhere in

most locations of the US and southern Canada.

WAAS

• Differential corrections are computed from ground stations and then

uploaded to geostationary satellites for broadcasting.

• WAAS-enabled GPS receiver automatically uses such correction data to

enhance the positional accuracy.

PDOP

Multipath

SNR

Sources of error

Source:Trimble

Multipath

• When GPS signals arrive at the receiver

having traveled different paths

What is a PDOP?

• Position Dilution of Precision

Good PDOP Poor PDOP

SNR (signal-to-noise ratio)

• SNR determines the signal strength relative to noise

• GPS position is degraded if the SNR of one or more satellites

in the constellation falls below certain range

Signal Strength

Indicators

Common use of GPS

A. GIS data collection & mapping

B. Navigation

C. Recreation

GPS for Navigation

GPS for Navigation

• GPS in PDA

are getting popular in car

comes with voice guidance.

GPS in Recreation

GPS in Farmland

Future GPS

A. GPS in USA

B. GLONASS program from Russia

C. GALILEO from European countries