Phase is the position of a point within the cycle of a wave, expressed in degrees (0–360°) or radians.¹ Two waves of the same frequency can differ in phase, meaning one is shifted in time relative to the other.

Phase is where a wave sits in its cycle; shifting phase is the basis of PSK digital modulation.

How it works

On the IQ plane, a sample’s angle is its phase and its distance from the origin is its amplitude. Deliberately jumping the phase between fixed values encodes data — the basis of phase-shift keying.

Relevance to SDR

Tracking phase is essential to demodulating PSK and QAM signals; a Costas loop recovers the carrier phase so symbols land correctly on the constellation.

Sources

1. Phase (waves) — Wikipedia, on the position within a wave’s cycle and phase difference. ↩

See also

• Amplitude
• IQ data
• Phase-shift keying (PSK)
• Constellation diagram

Learn it step by step

• IQ data & complex signals