A digital baseband modulator having a flexible architecture that is readily adaptible to a variety of digital modulation types is provided. A symbol builder maps the input data to a series of modulation states corresponding to data symbols that are represented as state indexes. A pair of digital filters accepts the state indexes being generated by the symbol builder to provide both up-sampling and filtering functions. The digital filters are implemented using random access memory (RAM) to implement blocks of interpolating look-up multipliers which may be readily configured between fast, normal, and long modes. The filtered output data from the digital filters is provided to a resampler that converts the filtered output data to an output sample rate that corresponds to the sample rate of output DACs and corresponding analog low pass filters.