The received signal may undergo various distortions and degradations during transmission, impacting both analog and digital signals. The three primary types of transmission impairments are attenuation, delay distortion, and noise.
Cause: Signal strength degrades with distance.
- The received signal needs sufficient strength for intelligent interpretation; and requires amplification or repeater.
- The signal must be maintained above the noise level to avoid errors; may need amplification or a repeater.
- Attenuation increases with frequency; an equalizer can mitigate frequency-dependent attenuation.
Solution: Amplifiers or repeaters to boost signal strength.
Cause: Velocity of signal propagation varies with frequencies.
Effect: Fast at the center frequency, falls off at frequency edges.
Solution: Equalization techniques to smooth out delay distortion.
Challenge: A timing jitter may occur, affecting the synchronization between the receiver clock and the incoming signal.
Cause: Unwanted signals inserted during transmission.
- Thermal Noise: Proportional to temperature and bandwidth.
- Intermodulation Noise: Caused by nonlinearity, producing unwanted frequency combinations.
- Cross Talk: Noise due to electrical coupling or unwanted signal pick-up.
- Impulse Noise: Irregular pulses with high amplitude, caused by lightning or faults.
- Cross-talk may lead to unintended eavesdropping on conversations.
- Impulse noise is especially problematic for digital data, causing distortion.
Solution: Mitigation strategies and error correction techniques.
Cause: Proportional to temperature and bandwidth.
Characteristics: Cannot be eliminated; an inherent factor in communication systems.
Understanding and addressing these transmission impairments is major for maintaining the quality and reliability of transmitted signals, whether they are analog or digital. Various techniques, such as amplification, equalization, and error correction, are employed to minimize the impact of these impairments on the received signal.