28-12-2012, 03:54 PM
Modulation
Modulation.ppt (Size: 331 KB / Downloads: 200)
Characteristics of Amplitude Modulation
Amplitude of the analog signal is modulated
One amplitude represents a 0
Another amplitude represents a 1
Frequency remains unchanged in both cases
Signals that are modulated at one end are demodulated at the other end
Usage
Amplitude is susceptible to interference
This technique in not normally used in modems
A variation of this technique is used in AM radio transmission
Analog-to-analog modulation takes place
Characteristics of Frequency Modulation
Frequency is modulated
Frequency f1
Represents 1
Frequency f2
Represents 0
The amplitude remains unaltered in both cases
Sample ITU Specifications
Modulation
ITU V.34
Error correction
ITU V.42
MNP 5
Data compression
ITU V.42 bis
MNP 2 to 4