1. In an amplitude modulation technique, amplitude of modulating signal is 0.5v and carrier amplitude is 1v. Find modulation index.
Answers
Answer:It is possible to vary the level of modulation applied to an amplitude modulated signal.
If little modulation is applied then the audio (assuming it us an audio transmission) will be difficult to hear. However if too much is applied, distortion can result and signals will not be easy to listen to and interference will increase and could affect users on nearby frequencies or channels.
As a result of this it is necessary to have a way of defining the level of modulation applied to an amplitude modulated signal.Two figures are used for this, namely the amplitude modulation, AM modulation index, and the modulation depth. Both are related, but they have slightly different meanings.
AM modulation index basics
The term, Modulation Index, is used for a number of forms of modulation, including AM.
For amplitude modulation, the modulation index is defined as the measure of extent of amplitude variation about an un-modulated carrier.
In other words it describes the amount by which the modulated carrier envelope varies about the static level.
Modulation Index, m=MA
Where:
A = the carrier amplitude.
M = the modulation amplitude and is the peak change in the RF amplitude from its un-modulated value.
Using the equation above it can be seen that a modulation index of 0.75 means that the signal will increase by a factor of 0.75 and decrease to 0.25 of its original level.
AM modulation depth basics
The amplitude modulation AM modulation depth figure is complementary to the modulation index.
Typically the modulation depth is the amplitude modulation index expressed as a percentage.
In this way an AM modulation index of 0.75 would be expressed as a modulation depth of 75%.
In reality the terms AM modulation index and the AM modulation depth are often used interchangeably, so there are often no hard and fast rules regarding their use.