Numerical - Power saving in AM when carrier and side band are suppressed

Numerical - Power saving in AM when carrier and side band are suppressed

Calculate the power saved in an Amplitude Modulated wave when it is transmitted with 45% modulation
- Without carrier
- Without carrier and a sideband

a.) 90%, 95%
b.) 82%, 91%
c.) 82%, 18%
d.) 68%, 16%

Correct Answer: a) 90%, 95%

Explanation:

The total power in an AM is given by
P_t= P_c ( 1 + m²/2)

Given: m= 0.45
Therefore P_t= P_c ( 1 +0.45²/2 )
P_t= P_c *1.10125
P_c/ P_t = 1/1.10125
= 0.908
= 90%

This shows that the carrier occupies 90% of total power. So 90% of total power may be saved if carrier is suppressed in the AM signal.

(ii) If one of the sidebands is also suppressed, half of the remaining power will be saved
i.e., 10/2 = 5 %. So a total of 95% (90% + 5% ) will be saved when carrier and a side band are suppressed.