Variable Frequency Electric Circuit Theory with Application to the Theory of Frequency-Modulation
John R. Carson, Thornton C. Fry · Bell System Technical Journal · 1937
In this paper the fundamental formulas of variable frequency electric circuit theory are first developed. These are then applied to a study of the transmission, reception and detection of frequency modulated waves. A comparison with amplitude modulation is made and quantitative formulas are developed for comparing the noise-to-signal power ratio in the two modes of modulation.