Physical Layer - Data Signals
Sine Waves
Sine waves can be made using the following function:
\[s(t)=A\sin(2\pi ft+\phi)\]Where:
- $A$ - Amplitude
- $f$ - Frequency
- $t$ - Time
- $\phi$ - Phase
- $T$ - Period ($\frac1f$)
Any signal can be made of many sine components.
Frequency Domain Representation
- You can plot the frequencies of a periodic signal on a bar graph to represent the signal. (Discrete)
- Aperiodic signals have continuous frequency domain representations.
If a signal has a spectrum with a zero frequency component (direct current), this is used as a voltage offset.
Bandwidth
The bandwidth of a signal is the upper and lower limit of the frequencies that can be represented in the medium.
A higher bandwidth gives more definition to analogue signals.
Advantages of Digital
- Digital is lower cost.
- Data integrity is preserved over longer distances with digital data.
- Repeaters can amplify the data without including line noise.
- High degree of multiplexing is easier with digital techniques.
- Increases utilisation.
- Data is easier to encrypt.