Suppose a signal travels through a transmission medium and its power is reduced to one-half.
This means that P2 is (1/2)P1.
In this case, the attenuation (loss of power) can be calculated as
A loss of 3 dB (–3 dB) is equivalent to losing one-half the power.
Delay distortion
it defines as the signal changes in its form or shapes.
Noise
noise the external energy that corrupts a signal.
types of noise :- 1) Atmospheric Noise.
2) Gaussian noise.
3) Cross talk
4) Impulse noise.
Atmospheric Noise:
- Lightning : static discharge of clouds..
- solar noise: sun's loinized gases.
- Cosmic noise: distant stars radiate high frequency signal.
Gaussian Noise:
- Thermal noise: generated by random motion of free electrons.
Crosstalk:
- NEXT (near-end crosstalk): Interface in a wire at the transmitting end of a signal sent on a different wire.
- FEXT (far-end crosstalk): Interface in a wire at the receiving end of a signal sent on a different wire.
Impulse Noise: Sudden bursts of irregular pulses. its a signal of high energy in a very short time.
