A QUADRATURE LOW-IF HOMODYNE RADIO RECEIVER

摘要

A single-ended homodyne receiver demodulates quadrature signals containingspectral nulls by using an extremely low intermediate-frequency that normallywouldcreate substantial self-interference. This is accomplished by judiciouslyplacing thespectral nulls over the critical sections of the signal spectrum, ensuringthat theself-interference is minimized. As an example, a direct-sequence CDMA signalthat wasconstructed with not more than one half the available Walsh functions isdemodulateddirectly by placing the intermediate frequency such that spectral nulls in theCDMAsignal overlap the spectral peaks in the desired signal, thereby eliminatingtheself-interference. This single-ended homodyne receiver can be implementedusing eitherintegrated or discrete components.