Advantages and Disadvantages of Standard Amplitude Modulation

Advantages of Standard Amplitude Modulation

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The following are the advantages of Standard Amplitude Modulation :

  1. AM transmitters are less complex .
  2. AM receivers are simple, detection is easy .
  3. AM receivers are cost efficient .
  4. AM waves can travel a longer distance .
  5. Low bandwidth

Applications of AM

  1. Radio broadcasting
  2. Picture transmission in a TV system

Disadvantages of Standard Amplitude Modulation

The disadvantages of standard Amplitude modulation or DSB-FC (Double sideband – Full Carrier ) system are as follows :

  1. Power wastage takes place in DSB-FC transmission
  2. DSB-FC system is bandwidth inefficient system
  3. AM wave gets affected due to noise

Now we will discuss each one in detail .

Power wastage in DSB-FC transmission

The carrier signal in the DSB-FC system does not convey any information . The information is contained in the two sidebands only .

But, the sidebands are images of each other and hence both of them contain the same information .

Thus, all the information can be conveyed by only one sideband .

As we know that the total power transmitted by an AM wave is given by :

eq26

eq27

Out of these three terms in the above equation , the carrier component does not contain any information and one sideband is redundant . Hence, out of the total power, the wasted power is given by :

eq28

This shows that we have to transmit much higher power than what is actually required . Hence, DSB-FC system is a power inefficient system .

Bandwidth Requirement of DSB-FC

The bandwidth (BW) of DSB-FC system is 2fm .  This is due to the simultaneous transmission of both the sidebands, out of which only one is sufficient to convey all the information .

Thus, the BW of DSB-FC is double than actually required and therefore, DSB-FC is a bandwidth inefficient system .

Effect of Noise

When the AM wave travels from the transmitter to receiver over a communication channel, noise gets added to it .

The noise changes the amplitude of the envelope of AM in a random manner .

As the information is contained in the amplitude variations of the AM wave, the noise will contaminate the information contents in the AM .

Hence, the performance of AM is very poor in presence of noise .