i)to increase the bandwidth of the signal
ii)to multiplex the signals
iii)to reduce the interferencemade when we transmit the
signals with nearly same frequency in the audio frequency
iv)to favour the complexity of the transmission system
for example if a person is sitting at the bus to go to hyd.
there is a bus which will go to the hyd. it is not the
matter that if the bus goes to the hyd he will also go.
he will also go to the hyd only when he sit in the bus.
here the bus is the carrier & the man is the information.
from this it is clear that modulation is why because the
information which is having less power can't travel large
distances that will put on the carrier which is having
large power that it can travel large distances.
1)in shortly it improves the signal strength . means the low
frequency signal can't transmit long distance here low
frequency signal means low strength (weak signal) ,when we
modulate that signal it can be transmitted long distance.
while it transmit long distance i.e., nothing but it's
strength s improves.
2) reduces noise or distortion.
3) multiplexing means we r using frequency translation theorem.
4) we transmit large amount of information at long
distances.i.e., narrow banding the signal.
5) reduce antenna height.
6) we can change the information from one form to another
form. i.e., encryption of data. thats whys we hiding the
information without any hackings.
BASIC NEED FOR MODULATION IS:
1.TO REDUCE ANTENNA HEIGHT
2.TRANSMIT THE INFORMATION TO MORE DISTANCE WITH OUT
3.TO REDUCE BAND WIDTH
EX:SUPPOSE IF U WANT THROUGH A PAPER HAVING INFORMATION TO
YOUR OPP APPARTMENT FROM YOUR APPARTMENT(EX:D=500cm)IF U
SIMPLY THROUGH A PAPER IT WILL NEVER REACH TO THE OPP
APPARTMENT BUT IF YOU USE A STONE.i.e COMBINELY WE CAN
THROUGH BECAUSE STONE HAVE WEIGHT LIKE WISE CARRIER HAVE
MORE POWER THAN BASE SIGNAL THAN WE CAN TRANSMITE THE
Modulation is a process in which the characteristics of a
signal circuit is caried in accordance with the information
signal which is to be transmitted.
The modulation signal,which is to be transmitted isknown
as Modulating signal.
Need for modulation:
ii)practicability of antennas height
an unknown semiconductor has Eg=1.1ev and Nv=Nc.it is doped
with 10^15 donors,where the donor level is 0.2ev below Ec.
given that Ef is 0.25ev below Ec, calculate ni and the
concentration of electrons and holes in the semiconductor at