Noise suppression system for AM using quadrature demodulation and Hilbert transformation

In recent years, interference of artificial noises from electrical power transfer becomes large and deterioration of sound quality of AM radio is worried. In this paper, a noise suppression system using quadrature demodulation techniques is proposed to reduce the effect of the interference. The proposed system utilizes the fact that the in-phase signal from the demodulator includes both of AM signal and interference, however, the quadrature signal includes only the interference. Thus, the interference in the in-phase signal could be canceled by the quadrature signal. Because of the sign of the both interference is different each other, Hilbert transformation is utilized to match the sign of the interferences. Validity of the proposed system is shown through computer simulation and experiments.