Analysis on the Definition Consistency Problem of EVM Measurement and its Solution

Abstract

The definition consistency problem of error vector magnitude (EVM) measurement is analyzed, and a solution using the peak-to-average ratio of the constellation diagram as a correction factor is proposed. Using different vector signal analyzers, the EVM values for 16-quadratic-amplitude modulation (QAM) and 64-QAM digitally modulated signals with certain distortions are measured. Furthermore, the corresponding theoretical EVM values are obtained through numerical simulation and analytical calculation. Comparing these results, it could be found that the definitions of EVM in different instruments are different. The essential reason is the different definition of EVM in the radio broadcast television technical standards and the wireless communication technology standards. This difference will lead to measurement errors and cognitive confusion. In order to solve this problem, a method using the peak-to-average ratio of the constellation diagram as a correction factor is proposed, and the experimental results proved that this solution is effective. At the same time, we strongly recommend the adoption of a unified EVM definition.