Not all signals behave the same over time. In this lesson, we’re diving into the concept of phase and how phase shift can modify the alignment of waves.

The phase of a signal is a measure that represents the shape of a sine wave at a specific moment. It’s usually expressed in degrees (from 0° to 360°) or in radians (from 0 to 2π).
But what does the number π have to do with our radio waves? Let’s take a trip back to trigonometry with this diagram:

No matter what the frequency of a signal is, its period (or cycle) always corresponds to a full rotation, either 360° or 2π.

Two signals are said to be in phase when their peaks and troughs line up; in other words, they oscillate together. This is called zero phase shift.

A phase shift is simply a difference in the timing or position of a wave. In basic terms, if two waves start at different times or reach their peaks at different moments, they are phase-shifted.
For example, if the phase shift is 180° (or π radians), one signal is exactly out of step with the other, this is known as phase opposition. In that case, the maximum amplitude of one signal aligns with the minimum of the other.

Alternatively, if the phase shift is 90° (or π/2 radians), one signal leads the other by a quarter cycle. This is called quadrature, meaning that the peak of one signal coincides with the zero crossing of the other.

And that’s a wrap on this quick lesson on phase. Understanding these basics will help when we dive into wave polarity later.