A.V. Zenkovich, V.L. Ballo, V.B. Dobrovolsky

A theoretical basis of the new principle of measurement of the signal-to-noise ratio is presented. The relationship between the mean-square noise amplitude modulation index of the mixture of signal and noise and the signal-to noise ratio is analyzed. This relationship is shown to be simple and definite, thus allowing one to calculate the signal-to-noise ratio by measuring the mentioned modulation index of the mixture of signal and noise. Only one instrument of domestic manufacture or made by a foreign brand is needed for the proposed measurement technique, namely, the modulation index meter or the modulation analyzer. The best results are expected with the instrument that measures the root-mean-square modulation index directly. Typically, such instruments allow smooth and wide frequency band operation from low frequencies up to 26,5 Gigahertz. When using the proposed technique, such elements of the traditional method for measuring the signal-to-noise ratio as signal and noise discrimination are eliminated, thus signal filtering is not needed anymore. The separate measurement of voltage or power of the signal and the noise is excluded thereby reducing the measurement error. The results of experimental verification and mathematical modeling of the proposed technique are presented in comparison with the known method. They prove the theoretical conclusion and the advantages of the proposed technique.