HOMODYNE DOWN-CONVERTER WITH DIGITAL HILBERT TRANSFORM FILTERING

摘要

A homodyne down-converter, for use in an IFsignal demodulator and the lake, includes ananalog-to-digital converter (ADC) which receives theIF analog signal for conversion to a digital datastream by sampling at a sampling rate frequencysubstantially equal to four times the IF signalfrequency. A digital mixer controllably inverts thesampled data to convert the data to baseband, before acircuit removes the effects of DC offset in the analogIF signal applied to the ADC. A discrete HilbertTransform filter is used for generating streams ofsequential in-phase I' and quadrature-phase Q' datawords, which are resampled to temporally align the twodata word streams at a new data rate, thus effectivelyremoving sample offset without the need for separatemisalignment correction circuitry.