Periodic analog signals can be classified as **simple or composite**. A simple periodic analog signal, a sine wave, cannot be decomposed into simpler signals. A composite periodic analog signal is composed of multiple sine waves.

- Sine Wave
- Wavelength
- Time and Frequency Domain
- Composite Signals
- Bandwidth

Sine Wave is the most fundamental form of a periodic signal.

**Frequency**

Frequency is the rate of change with respect to time.

Change in a short span of time means high frequency.

Change over a long span of time means low frequency.

**Phase**

Phase describes the position of the waveform relative to time 0.

**Signals and Communication**

A single-frequency sine wave is not useful in data communications.

We need to send a

**composite signal**, a signal made of many simple sine waves.According to Fourier analysis, any composite signal is a combination of simple sine waves with different frequencies, amplitudes, and phases.

**Composite Signals and Periodicity**

If the composite signal is periodic, the decomposition gives a series of signals with discrete frequencies.

If the composite signal is nonperiodic, the decomposition gives a combination of sine waves with continuous frequencies.

**Bandwidth**

The bandwidth of a composite signal is the difference between the highest and the lowest frequencies contained in that signal.