Field Guide · term

Also known as: IQ data, IQ samples

IQ data is the stream of paired numbers an SDR produces — I (in-phase) and Q (quadrature, 90° apart). Together each pair captures both the amplitude and phase of the signal at that instant.1

IQ phase amplitude
Each IQ sample is a point on the complex plane: distance from the origin is amplitude, angle is phase.

How it works

Treating each sample as a point (I, Q), its distance from the origin is amplitude and its angle is phase — the basis of the constellation diagram. IQ also lets a receiver distinguish frequencies above and below the tuned centre.

Relevance to SDR

Everything GopherTrunk does begins with the IQ stream from the radio: tuning, filtering, demodulation, and the scopes all operate on it.

Sources

  1. In-phase and quadrature components — Wikipedia, on representing a signal as paired I and Q components. ↩

See also

Learn it step by step

From the blog