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Figure (EP) shows a communication system...

Figure (EP) shows a communication system. What is the output power when input signals is of 1.01 mW? [ gain in `dB = 10 log_10(P_0//P_t)]`.

A

90mW

B

101mW

C

1112mW

D

120mW

Text Solution

Verified by Experts

The correct Answer is:
B

Here, transmission path =5km
Loss suffered in transmission path
`=-2dB km^(-1)xx5km=-10dB`
Total amplifier gain =10dB+20dB=3 0dB
Overall gain of singal =30dB-10dB=20dB
As, gain in `dB=10"log"_(10)((P_(0))/(P_(i))): therefore 20=10"log"_(10)((P_(0))/(P_(i)))`
or `"log"_(10)((P_(0))/(P_(i)))=(20)/(10)=2="log"_(10)100` or `(P_(0))/(P_(i))=100`
or `P_(0)=P_(i)xx100=1.01 mWxx100=101mW`
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