Telecommunication
Technology
Transmitter
In electronics and telecommunications a transmitter or radio
transmitter is an electronic device which produces radio waves with an antenna.
(Wikipedia)
1st step of sending a massage
Communication
channel
Medium
of sent electrical signal one place to another place.
Type
of media
1. Electrical conductor
2. Fiber optic cable
3. Free space(wireless)
For more
information about type of transmission media[Visited 2019.12.13]
Gain
Means
amplification
Symbol
– A
No
Unit
Av
–Voltage gain
Ap
– Power gain
Av
= Vout/Vin
Ap
= Pout/Pin
Cascaded
Amplifiers
If
two or more amplifiers are connected with together it called cascaded
amplifiers.
In
this,
Total Gain (At) = A1 x A2 x A3 x …An
For more information[visited 2019.12.13]
Signal
Attenuation
The
loss of signal strength.
·
Reduce
the signal amplitude
·
Represented
by A like gain
·
If
A is less than 01, then the circuit has attenuation.
Av
= Vout/Vin
Ap
= Pout/Pin
Total
Attenuation (At) = A1 x A2 x A3 x …An
v If circuit has both gain and
attenuation,
Total gain and attenuation will
be,
(At) = A1 x A2 x A3 x …An
Total
gain and attenuation in dB
At
(dB) = A1+A2+A3+…..An
Important
: Power gain in dB = 10 log (Pout/Pin)
Voltage gain in dB = 20 log (Vout/Vin)
Signal
to Noise Ratio (SNR)(S/N)
v Measure of noise
v Expressed in decibels (dB)
Ø Signal Power = Ps
Ø Noise Power = Ns
SNR =10 log( Ps/Ns)
v Very high SNR is preferred for
best performance.
v Communication equipment is design
to produce the highest feasible SNR.
It
is difficult to measure SNR, so how can we calculate it??????
It
may possible to measure the noise power by turn off the signal but it is not
possible to turn off the noise in order to measure signal power.
Input
signal power + nose power = output signal power (Ps)
(S+N)/N
SNR = 10 log ((S+N)/N)
Noise
ratio (NR)
NR
= (S/Ni)/(S/No) S/Ni - input
SNR,S/No – output S/No
Noise figure (NF)
NF
= 10 log( NR) , NF = 10 log ((S/Ni)/(S/No))
If
all the elements in dB,
NFdB = (S/Ni)dB
- (S/No)dB
