Alias-Free Digital Synthesis of Classic Analog Waveforms
Timothy S. Stilson, Julius O. Smith · 1996
Techniques are reviewed and presented for alias-free digital synthesis of classical analog synthesizer waveforms such as pulse train and sawtooth waves. Techniquesdescribed include summation of bandlimited primitive waveforms as well as table-lookup techniques. Bandlimited pulse and triangle waveforms are obtained by integrating the difference of two out-of-phase bandlimited impulse trains. Bandlimited impulse trains are generated as a superposition of windowed sinc functions. Methods for more general bandlimited waveform synthesis are also reviewed. Methods are evaluated from the perspectives of sound quality, computational economy, and ease of control. 1 Introduction Any analog signal with a discontinuity in the waveform (such as pulse train or sawtooth) or in the waveform slope (such as triangle wave) must be bandlimited to less than half the sampling rate before sampling to obtain a corresponding discrete-time signal. Simple methods of generating these waveforms digitally contain...