Abstract :
This paper discusses the derivation, limitations, and use of system equations relating input and output signal/noise ratios in fm detection with band-pass and with low-pass output filters and in fm/fm multiplex transmission. The fm/fm equation is: (S/N)D = (S/N)c (3/4)½ (fDC/fS) (fDS/FUD) where (S/N)D is the output (data voltage) rms signal/noise ratio, (S/N)C is the input (radio carrier channel) rms signal/noise ratio, BC is the input (radio carrier channel) bandwidth, FUD is the output (data voltage) low-pass filter bandwidth, fDC is the peak deviation of the carrier due to the subcarrier, fS is the center frequency of the frequency-modulated subcarrier, and fDS is the peak deviation of the subcarrier due to the data voltage (assumed a sine wave).
