A quadrature low-IF homodyne radio receiver

摘要

A single-ended homodyne receiver demodulates quadrature signals containing spectral nulls by using an extremely low intermediate-frequency that normally would create substantial self-interference. This is accomplished by judiciously placing the spectral nulls over the critical sections of the signal spectrum, ensuring that the self-interference is minimized. As an example, a direct-sequence CDMA signal that was constructed with not more than one half the available Walsh functions is demodulated directly by placing the intermediate frequency such that spectral nulls in the CDMA signal overlap the spectral peaks in the desired signal, thereby eliminating the self-interference. This single-ended homodyne receiver can be implemented using either integrated or discrete components.