EVM to SNR Calculator

This tool converts from Error Vector Magnitude (EVM) to Signal-to-Noise Ratio (SNR).

In order to calculate SNR the following are required:

  • EVM% (use this tool to convert from dB to %)
  • Peak-to-Average Power Ratio (PAPR). Use the table below to find the PAPR of a modulated signal. In the case of OFDM waveforms use this tool.

Formula

SNR = – [PAPR + 20 * log10 (EVM% / 100)]

Example EVM to SNR calculation

If you want to calculate the SNR for QPSK waveform for instance, use the PAPR value of 1.76 dB from the table below in the calculator above.

For a 1% EVM, the SNR is 38.24 dB. As the EVM increases the SNR degrades and at a certain point it will become difficult to demodulate the signal.

Peak-to-Average-Power-Ratio Values

Below is a table of PAPR values for different modulation formats. These can be used in the calculator.

WaveformPAPR (dB)
Sine Wave3.01
Full-wave rectified sine3.01
Half-wave rectified sine6.02
Triangle wave4.77
PWM signal10*log10(T/dT)
QPSK1.76
8-PSK3.3
π⁄4-DQPSK3
OQPSK3.3
64-QAM3.7
\infty -QAM4.8
WCDMA downlink carrier10.6
OFDM12
GMSK0
Gaussian noise\infty
Periodic chirp3.01
Peak-to-average-power of different signals

References

  1. Crest Factor on Wikipedia