误差矢量幅度（Error Vector Magnitude，EVM），是误差矢量平均功率与参考信号的平均功率之比的平方根。

EVM一般用来评估发射机发射信号的调制质量，避免了用多个参数来表征发送射频信号，在开发设计过程中是一个很有价值的整个信号质量的指示器。在WiMAX 802.16-2004和802.16e-2005协议里面，使用的是一个新的术语——相对星座图误差（RCE），EVM一般用百分数或者dB数来表示，其换算关系如下。

例如，3%的EVM用对数表示为 -30.5dB。

The error vector magnitude or EVM (sometimes also called receive constellation error or RCE) is a measure used to quantify the performance of a digital radio transmitter or receiver. A signal sent by an ideal transmitter or received by a receiver would have all constellation points precisely at the ideal locations, however various imperfections in the implementation (such as carrier leakage, low image rejection ratio, phase noise etc.) cause the actual constellation points to deviate from the ideal locations. Informally, EVM is a measure of how far the points are from the ideal locations.