EVM: Why it Matters and how it’s Measured

In Wi-Fi networks, successful data transmissions depend on the performance of the transmitter, the receiver and the air interface in-between. Because the air interface cannot be controlled, during device development and manufacturing the focus is placed on ensuring high performance of the transmitter and receiver chains. New Wi-Fi generations have increased the modulation constellation size with 1024-QAM and 4096-QAM, placing an even higher requirement into transmitter accuracy. 

EVM (Error Vector Magnitude) is the key metric used to evaluate transmitter performance, because it provides a consistent “yardstick” to characterize the transmitter regardless of the receiver implementation and it encapsulates a wide range of possible impairments on the transmitter chain into a single measurement. This application note provides the necessary background to understanding why and how EVM is measured.