Error Vector Magnitude (EVM) RMS to dB Calculator

This tool allows you to calculate the Root mean square value of EVM to its dB equivalent. It also computes the dB value from RMS.

Formula

EVMRMS = 100 * 10^(EVMdB/20)

EVMdB = 20 * LOG10^(EVMRMS/100)

How to use the calculator

EVM is a measure of modulation quality of a communication system. Enter a number in either field of the tool. The dB value should be a negative number lower than zero. The percent value should be a number between 0 and 100.

The lower the value of EVM either in percentage or dB, the lower the error. This translates directly to lower Bit error rate and higher quality signals.

Example calculations

A value of -40 dB translates to 1% EVM.

What is a good value of EVM?

The answer depends on the modulation format and target performance levels. For 802.11 Wi-Fi systems, the IEEE for instance requires -30 dB EVM for 256 QAM modulation and coding rate of 3/4. As the modulation constellation size increases from 256 to higher, the target EVM becomes lower.

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