Q. Illustrate Signal attenuation?

Signal attenuation in many channels can be offset by using amplifiers to boost the signal level during transmission. However, the amplifier also introduces additive noise in the process of amplification, thereby corrupting the signal. The additional noise must also be taken into consideration in the design of the communication system.

Any conductive two-terminal device is characterized generally as lossy, with some resistance R. A resistor, which is at a temperature τ above absolute zero, contains free electrons that exhibit randommotion and, thus, result in a noise voltage across the terminals of the resistor. Such a noise voltage is known as thermal noise. If the noise is introduced primarily by electronic components and amplifiers at the receiver, it may be characterized as thermal noise.