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CHAPTER 3 - Coggle Diagram
CHAPTER 3
Components of RF communications
Transmitter
The initial components in the creation of the
wireless medium.
Generates signal at specific frequency
Determines amplitude (power level) of signal
The computer hands the data off to the transmitter, and it is the transmitter’s job to begin the RF communication
The transmitter takes data provided and modifies the AC signal by using a modulation techniques to encode the data into signal.
Receiver
Receives the signal from the antenna and
translates the signal into 1s and 0s.
It then takes this data dan passes it to the
computer to be processed.
It is not easy job.
This signal that is received is a much less powerful signal that what was transmitted because of distance it has traveled and the effect of free spaces path loss (FSPL)
Antenna
Provides two functions in a communication
system.
When connected to the transmitter,it collects AC signal that it receives from the transmitter and directs,or radiates,the RF waves away from the antenna in a patern specific to the antenna type.
When connected to the receiver,the antenna take the RF waves that it receives through the air and directs the AC signal to the receiver.
The receiver converts the AC signal to bits and
bytes
Generate more power at transmitter
Direct or focus,the RF signal that is
radiating from antenna
Isotropic radiator
Intentional radiator (IR)
Specifically designed to generate RF.
Consists of all components from transmitter to antenna (such as the transmitter, amplifiers, cables, and other knobs and dials found in wireless devices), excluding antenna
A device that intentionally generates and emits radio frequency energy by radiation or induction
It measured in miliwatts(mW)
Cordless phones, walkie-talkies, and wireless
cards are all good examples of Irs.
Equivalent isotropically radiated power (EIRP)
Highest RF signal strength transmitted
from antenna.
Focuses the RF generated by the IR and
makes it stronger.
A measure of the amount of actual power
emitted from an antenna.
The isotropy in EIRP describes an ideal situation whereby the radio energy is assumed to be equally distributed in all directions.
It is the sum total of the power output from the IR and the passive gain (or loss) caused by the antenna.
Units of power and comparison
Units of Power
1/1,000 of a watt
Milliwatt (mW)
Decibels relative to 1 milliwatt (dBm)
Compares signal to 1 milliwatt of
power
0 dBm = 1 milliwatt
1 Watt = 1 ampere (amp) of current
flowing at 1 volt
Amp is current
Voltage is pressure generated
Amount of watts generated =
volts X amps
Watt
Units of Comparison
Represents difference btw 2 values
Decibel (dB)
Gain or increase of power from an antenna when compared to what an isotropic radiator would generate
Decibels isotropic
Increase in gain of an antenna when it is compared to the signal of a dipole antenna
If antenna has value of 3 dBd, it is 3
dB greater than a dipole antenna
Decibels dipole (dBd)