Question

You connected your PC to a projector or printer, which is located 20 m away and transmitted a signal x(t) from the PC to the receiver through USB cable. State and briefly explain three impairments the signal x(t) may likely experience as it propagates through the transmission channel

Answer 1

Three impairments the signal is likely to experience are:

1. Attenuation : Attenuation basically means loss of energy. The strength of signal decreases as the distance increases which causes loss of energy in overcoming the resistance provided by the medium. This is also known as attenuated signal. Factors affecting attenuation are : The received signal should have sufficient strength to be interpreted by a receiver. The signal should be at a level higher than the noise so that error will not be generated. An amplifier or a repeater can be used.

2. Delay Distortion :  It means changes in the form or the shape of the signal. This is usually seen signals which are made up of different frequencies. Each frequency component has a different propagation speed travelling through a medium and thats why there is a delay in arriving at the destination. Every component arrives at different time and this leads to distortion. Delay distortion is a major reason for the timing jitter problem.

3. Noise : The unwanted signal which mixes up with the original signal is called noise. There are several types of noise such as induced noise, crosstalk noise, thermal noise and impulse noise which may corrupt the signal. Induced noise comes from sources such as appliances. These act as senders and the transmission medium act as a receivier. Thermal noise is a function of temperature and bandwidth. It cannot be eliminated. Crosstalk noise is caused by electrical coupling in the near by twisted pair or by unwanted signal picked by microwave antennas.