Answer / jyoti sheoran

MODULATION IS A SCHEME WHICH ALTERS SOME CHARACTERISTICS OF
THE HIGH FREQUENCY CARRIER IN ACCORDANCE WITH THE LOW
FREQUENCY MESSAGE SIGNAL CALLED THE MODULATING SIGNAL.

THERE ARE THREE TYPES OF MODULATION :-

1). AMPLITUDE MODULATION(AM) :-
IN THIS TYPE OF MODULATION
FREQUENCY AND PHASE REMAINS SAME, ONLY THE AMPLITUDE
CHANGES.

2). FREQUENCY MODULATION(FM) :-
IN FM THE PEAK AMPLITUDE
AND PHASE REMAINS CONSTANT BUT AS THE AMPLITUDE OF THE
INFORMATION CHANGES, THE FREQUENCY OF THE CARRIER CHANGES
CORRSEPONDINGLY.

3). PHASE MODULATION(PM) :-
PM IS USED IN THE SAME SYSTEM
AS AN ALTERNATIVE TO FREQUENCY MODULATION. IN PHASE
MODULATION, THE PHASE OF THE CARRIER SIGNAL IS MODULATED TO
FOLLOW THE CHANGING VOLTAGE LEVEL OF THE MODULATING SIGNAL.

NEED FOR MODULATION :-

1: EFFICIENT RADIATION
2: FREQUENCY TRANSLATION
3: MULTIPLEXING
4: REDUCTION OF NOISE

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