Digital waveform generating apparatus

Claim 1

Digital waveform generating apparatus for generating a signal of a desired waveform at a selected frequency within a frequency range comprising generating means for generating a first data word whose digital value corresponds to said selected frequency; accumulating means for storing a second data word corresponding to a data memory address; adding means for adding the first data word to the second data word and storing the result in said accumulating means as an accumulated second data word; waveform storage means for storing a plurality of waveform data words corresponding to said desired waveform, each of said waveform data words being stored at a predetermined respective data memory address therein; clock means providing a timing signal of fixed frequency; and control means responsive to said timing signal for controlling said accumulating means and for addressing the waveform data words stored in said waveform storage means in accordance with the accumulated second data word stored in said accumulating means upon occurrence of said timing signal so that the addressed waveform data words are read out from said waveform storage means as said output signal; wherein, to avoid a folded error in the output signal, said waveform storage means is partitioned into a plurality of data banks each corresponding to a predetermined portion of said frequency range and each storing a corresponding plurality of waveform data words therein, with each such plurality of waveforms data words representing waveforms having progressively fewer harmonics as the frequency of the corresponding portion of the frequency range increases, and said control means includes means for selecting one of said data banks in accordance with the particular portion of the frequency range containing said selected frequency to provide as said output signal its waveform data words in response to said accumulated second data words.