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16 Νοε 2013 (πριν από 4 χρόνια και 5 μήνες)

102 εμφανίσεις

F
ACULTY

OF

C
OMPUTER

S
CIENCE

&
E
NGINEERING

Frequency

F
ORMATION

OF

R

F
REQUENCY

Carrier Wave is Sin signal have high frequency
in which it will have components such as phase
or amplitude will vary according to the signal
wave, waves to create high
-
rise to bring these
signals in space

F
ORMATION

OF

R

F
REQUENCY

O
BJECTIVES

Questions about the waves?

Wave mechanics of natural

Concept

Amplitude

Wave length

Phare

Cycle

Frequency

O
BJECTIVES

Formation Of Electromagnetic Waves

Electric Fields

Magnetic Fields

Electromagnetic Fields

Electromagnetic Waves And Radio Communication

The Operation Of The Radio Waves

Concept Carrier Wave

Modulation methods Carrier Wave

Frequency range of applications in wireless media.

O
BJECTIVES

RF Behaviors

Gain

Loss

Reflection

Refraction

Diffraction

VSWR

The Units Used In Radio Communication

Q
UESTIONS

THE

WAVES
?

What is the wave ?

What is the shape wave ?

How is the wave active ?

Define of Amplitude, Cycle, Frequency, Phase

What is bandwidth? What frequency band?

What is 3G , GSM ,CDMA ……?

Q
UESTIONS

THE

WAVES
?

Why do we hear the sound coming from far away?

Why do we listen to the radio at night better normal?

Why do we communicate with each other via phone ?

Why was the data transmitted through outer space ?

We want to watch TV, listen to the radio antenna
must be why?

Meaning of UHF, VHF .

W
AVE

MECHANICS

OF

NATURAL

W
AVE

MECHANICS

OF

NATURAL

For waves on the water above, the oscillation
perpendicular to the direction of wave
propagation. It is the shear wave

Has the oscillation wave coincides with that of
wave propagation along the wave.

Sound waves as we speak, it is a longitudinal
wave

RF C
HARACTERISTICS

All RF waves have characteristics
that vary to define the wave. Some of
these properties can be modified to
modulate information onto the wave.
These properties are
wavelength,
frequency, amplitude,
and
phase.

A
MPLITUDE

Amplitude is high, the strength or power of the
wave

W
AVELENGTH

Wavelength is the distance between two points
on two similar consecutive wave crests

P
HASE

C
YLE
, F
REQUENCY

What cycle? What is the frequency? Frequency is
the number of vibrations per unit time and is
equal to f = 1 / T. Longer period is the time to
perform a full oscillation.

C
YLE
, F
REQUENCY

The impact of frequency usage on WLANs is
tremendous. By using different frequencies, you
can enable distinct connections or RF links in a
given coverage area or cell. For example, an
IEEE 802.11g network using channel 1 can exist
in the same cell as an IEEE 802.11g network
using channel 11. This is because these channels
use different frequencies that do not cancel or
interfere with each other.

S
OUND

WAVES

AND

S
OUND

FEELINGS

Example :

When you shake a piece of mild steel plates that we found
lower vibration

When we rung steel plate with a larger force

Ears begin to hear a certain gently, that is, pieces of steel that
has a sound start

Human ear is sensing the oscillation frequency from about
16Hz to 20.000Hz.

Sound waves in any solid, liquid, gas

Mechanical waves with frequencies greater than 20.000Hz
called ultrasonic

E
LECTROMAGNETIC

W
AVES

An electromagnetic wave is a propagating combination
of electric and magnetic fields.

In terms of nature, electricity and magnetism are
manifestations of a separate unified field called
electromagnetic fields

E
LECTRIC

F
IELDS

Example :

When an AC is running. It immediately
generates an electric field around it

In general the electric field is the physical
environment surrounding the special charge

In terms of nature, electricity and magnetism are
manifestations of a separate unified field called
electromagnetic fields

M
AGNETIC

F
IELDS

Example :

When an AC is running. We move the wires of
the electric current is running. It immediately
generates a magnetic field.

In terms of nature, electricity and magnetism are
manifestations of a separate unified field called
electromagnetic fields

E
LECTROMAGNETIC

W
AVES

Principle
Macxoen

Electromagnetic field due to a charge of vertical
vibrations generated at O will spread in space as
waves. Wave which is called electromagnetic waves.

Hecxo

the first to develop the electromagnetic wave

The velocity of electromagnetic waves is 300.000km/s.
Coincides with the velocity of the light

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

Applications of Electromagnetic waves :

-
controlled

In the radio communication

Waves with frequencies from thousands hectares or
more, known as radio waves.

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

The radio waves are classified into the following
categories

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

Characteristics of waves :

Long and ultra long wave

Less water absorption

They are used to communicate underwater

Normal wave

During the day they are strongly absorbed by the
ionosphere, so far not been transmitted

So the night medium wave radio better day

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

Characteristics of waves :

Short wave ( Microwave)

They are reflective ionosphere on the ground

So a short radio stations with large capacity can wave to all
locations on the ground.

Supper Short wave ( Microwave)

The microwave has the largest energy

Ionosphere are not absorbed or reflected

Used in information space

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

Man
-

Principles of operation of a radio transmitter

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

E
LECTROMAGNETIC

WAVES

AND

COMMUNICATION
.

High
-
frequency waves is called carrier

Carrier Wave is Sin signal have high frequency
in which it will have components such as phase
or amplitude will vary according to the signal
wave, waves to create high
-
rise to bring these
signals in space

M
ODULATION

METHODS

Definition digital

Digital data

Analog data

Digital data

Digital signal

Analog signal

Analog data

Digital signal

Analog signal

M
ODULATION

METHODS

Vary amplitude call amplitude

Vary frequency call frequency

Vary
phare

call
phare

Modulated at the digital data:

Amplitude Shift Keying

Frequency Shift Keying
-

FSK

Phase Shift Keying

PSK

M
ODULATION

METHODS

M
ODULATION

METHODS

Modulated at the analog data:

AM (Amplitude Modulation)

FM (Frequency Modulation)

PM (Phase Modulation)

M
ODULATION

METHODS

RF B
EHAVIORS

RF

waves

that

have

been

modulated

to

contain

information

are

called

RF

signals
.

These

RF

signals

have

behaviors

that

can

be

predicted

and

detected

Gain

Loss

Reflection

Refraction

Diffraction

Scattering

VSWR

RF B
EHAVIORS

GAIN

Increase in an RF signal's amplitude.

Conventional amplifier is an active process

But the process is passive amplification can
occur.

RF B
EHAVIORS

RF B
EHAVIORS

LOSS

Described as the decline of signal strength

There are many causes of the radio wave
attenuation

RF B
EHAVIORS

RF B
EHAVIORS

Reflection

When an RF signal bounces off of a smooth,
nonabsorptive

surface, changing the direction of
the signal, it is said to
reflect
and the process is
known as
reflection.

RF B
EHAVIORS

RF B
EHAVIORS

Refraction

Refraction occurs when an RF signal changes
speed and is bent while moving between media of
different densities.

RF B
EHAVIORS

RF B
EHAVIORS

Diffraction is often caused by buildings, small
hills, and other larger objects in the path of the
propagating RF signal.

RF B
EHAVIORS

RF B
EHAVIORS

VSWR

RF B
EHAVIORS

Voltage Standing Wave Radio

VSWR values are often found to be 1.5: 1

EX:

1:1 VSWR value combination perfect impedance

Influence VSWR

Reduce the amplitude of radio waves

This capacity can burn the circuit area

RF B
EHAVIORS

Solutions for VSWR

Never use a cable to a device 75 Om 50 Om cable

The equipment needs to be synchronized

R

F
REQUENCY

M
ATHEMATICS

There are four parameters are calculated in the
WLAN:

Power at the transmitting device

The attenuation and amplification devices connected

Capacity at the last connector before the antenna

Power at the antenna elements (EIRP)

R

F
REQUENCY

M
ATHEMATICS

W (Watt)
of the basic unit of power is Watt (W)

1 W is defined as an electric current is 1 A and 1
V

EX:

Light used 120 V will have 7 W.

In a totally dark 7W bulb is visible from about 83 km
away from it in all directions

R

F
REQUENCY

M
ATHEMATICS

Miliwatt

(
mW
)

Often, the power level of WLAN rarely exceed
100
mW

100
mWcan

transmitting data to 0.8 km

1 W= 1000
mW

R

F
REQUENCY

M
ATHEMATICS

Units of dB and
dBm

Measurement Units amplification and
attenuation

Unit
dBm

is a unit of absolute power

R

F
REQUENCY

M
ATHEMATICS

Have unit conversion table as follows

R

F
REQUENCY

M
ATHEMATICS

EX: Transfer from
dBm

to W units

We have 43 = 10 + 10 + 10 +10 + 3

So infer

10
dBm

based on the first panel would be 10
mW

Or 1mW x 10 = 10
mW

10mW x 10 = 100
mW

100
mW

x10 = 1000mW

1000mW x 10 = 10,000
mW

10,000mW x2 = 20,000
mW

= 20 W

R

F
REQUENCY

M
ATHEMATICS

Unit
dBi

Amplification antenna

The
END