Digital Generation of Low-Frequency Sine Waves

Generation of approximately sinusoidal waveforms by a digital method is described. Very low frequencies (below 1 Hz) are easily obtained without the use of large inductors or capacitors, and the method is fully compatible with integrated circuit techniques. A process equivalent to nonrecursive digital filtering is used to remove the majority of harmonics from a binary waveform generated by a feedback shift register, leaving the fundamental together with only a few high-order harmonics of small amplitude.