Wideband FM Demodulation and Multirate Frequency Transformations

Abstract : Conventional narrowband demodulation approaches assume that the signal of interest is narrowband, i.e., with bandpass spectral content confined to a bandwidth that is much smaller in comparison to the carrier frequency. However if the signal of interest is a wideband signal, the underlying assumptions are violated and these approaches incur significant demodulation error. In this report, we summarize the proposed wideband demodulation approach that employs multirate frequency transformations to convert the wideband signal to a narrowband signal so that conventional demodulation algorithms can be applied. The information signals associated with the wideband input are obtained via the inverse multirate frequency transformation. We then outline an approach that employs multirate Noble identities to extend the proposed approach to larger wideband to narrowband conversion factors and more practical implementations. We further detail its application to the associated problems of wideband image demodulation, wideband speech formant demodulation, and wideband demodulation. These applications demonstrate the efficacy of the wideband demodulation approach.