What is EVM?
EVM is the key RF quality metric that quantifies how accurately a transmitter reproduces a target digital modulation signal. It measures the vector difference between each actual transmitted symbol and its ideal reference position on the IQ constellation, expressed as a percentage or in dB. EVM is the primary indicator of transmitter impairments including phase noise, IQ imbalance, and amplifier nonlinearity.
How Does EVM Work?
At each symbol period, the error vector is the difference between the ideal symbol position and the actual received/transmitted symbol in the IQ plane. EVM is the RMS magnitude of all error vectors, normalised to the reference signal power. 5G NR requires EVM ≤ 3.5% for 256-QAM and is studying sub-1% EVM for 1024-QAM (Release 16).
Use Cases
Transmitter quality verification in base station and UE conformance testing, power amplifier linearisation assessment, validation of 256-QAM/1024-QAM capability.
3GPP / Standards Reference
3GPP TS 38.104 (BS Radio Requirements), TS 38.101-1 (UE Radio Requirements, FR1)
Related Terms
QAM | ACLR | OTA | Modulation
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
