Estimation of single-to-noise ratio by processing measured error vector magnitude

摘要

The signal-to-noise ratio of a demodulated received signal is estimated by measuring the error vector magnitude (EVM) of the demodulated signal; and processing the measured EVM in combination with a correction term to estimate the signal-to-noise ratio of the demodulated signal. The correction term is a polynomial function of the measured EVM. The signal-to-noise ratio is estimated in accordance with the formula: $\frac{E_S}{N_0}\cong 10.{\mathrm{LOG}}_{10}\left(\frac{\mathrm{pi}.\lceil E_S\rceil }{{4\left[{\widehat{\mathrm{mu}}}_z+C\left({\widehat{\mathrm{mu}}}_z\right)\right]}^2}\right)\left(\mathrm{dB}\right)$ wherein {circumflex over (mu)}_z is the measured EVM based on the mean of a Rayleigh density of EVM measurements; and C is the correction term. For QPSK modulated signals, C is calculated in accordance with the formula: C_QPSK({circumflex over (mu)}_z)≅2.71x10^-3{circumflex over (mu)}_z³-7.54x10^-2{circumflex over (mu)}_z²+0.7{circumflex over (mu)}_z-2.25. For BPSK modulated signals, C is calculated in accordance with the formula: C_BPSK({circumflex over (mu)}_z)≅1.78x10^-4{circumflex over (mu)}_z³-1.03x10^-3{circumflex over (mu)}_z²+4.62x10^-2{circumflex over (mu)}_z-0.588.