Harada, T., Hattori, Y., Ito, S., Fujimoto, M. et al., "Noise Suppression System for AM Radio Receiver Using Quadrature Component of Receiving Signal," SAE Int. J. Passeng. Cars – Electron. Electr. Syst. 9(1):147-152, 2016, doi:10.4271/2016-01-0079.
Recently, the electromagnetic interference in an AM radio by the noise generated from a power control unit (DC-DC converters, inverters) in a hybrid vehicle (HV) has become a serious problem. To solve the problem, most noise suppression methods, for example, use noise filters for noise sources and shield wiring and ferrite cores for noise propagation paths. In this paper, we propose a noise suppression method using the digital signal processing in an AM radio receiver. In this method, first the receiving AM radio signal containing HV noise is quadrature demodulated. Next, a replica signal of the noise is generated by using the noise signal in the quadrature component. Then, the replica signal is subtracted from the AM radio signal containing the noise of the in-phase component. We construct a prototype of the radio receiver system based on this method and demonstrate that the system can reduce the HV noise superimposed on the AM radio signal by more than 20 dB. By applying this system to the radio receiver, it is expected that conventional noise suppression methods can be significantly simplified.