Vector signal analyzer

The primary use is to make in-channel measurements, such as error vector magnitude, code domain power, and spectral flatness, on known signals.

[1] These measurements are used to determine the quality of modulation and can be used for design validation and compliance testing of electronic devices.

A portion of the input signal spectrum is down-converted[broken anchor] (using a voltage-controlled oscillator and a mixer) to the center frequency of a band-pass filter.

Usually there is a windowing function option to limit spectral leakage and enhance frequency resolution.

By representing the quadrature and in-phase components as the vertical and horizontal axes, the error vector magnitude can be computed as the distance between the ideal and measured constellation points on the diagram.