Topic: Digital Communications
The eye diagram of a digital communication system closes vertically and horizontally due to
- A. Inter-symbol interference only
- B. Timing jitter and ISI
- C. AWGN only
- D. Synchronization drift only
Answer: B. Timing jitter and ISI
Explanation: In an eye diagram, the vertical opening indicates the system's immunity to noise and is reduced primarily by Inter-Symbol Interference (ISI) and additive noise. The horizontal opening represents the time interval over which the signal can be reliably sampled and is reduced by timing jitter and phase variations. Therefore, the diagram closes both vertically and horizontally due to the combined effects of Timing jitter and ISI.