In the wavetable formulation, a pulse train can be made by a stretched
wavetable:

where is the phase, i.e., the value wrapped to lie between and . The function should be zero at and beyond the points and , and rise to a maximum at 0. A possible choice for the function is

which is graphed in part (a) of Figure 6.4. This is known as the

Realizing this as a repeating waveform, we get a succession of (appropriately sampled) copies of the function , whose duty cycle is (parts b and c of the figure). If you don't wish the copies to overlap the index must be at least 1. If you want to allow overlap the simplest strategy is to duplicate the block diagram (Figure 6.3) out of phase, as described in Section 2.4 and realized in Section 2.6.