The shape of the pulse wave is defined by its duty cycle D, which is the ratio between the pulse duration () and the period (T).A pulse wave or pulse train is a kind of non-sinusoidal waveform that is similar to a square wave, but does not have the symmetrical shape associated with a perfect square wave.It is a term common to synthesizer programming, and is a typical waveform available on many synthesizers.he Fourier series expansion for a rectangular pulse wave with period T and pulse time τ is. Note that, for symmetry, the starting time (t = 0) in this expansion is halfway through the first pulse. The phase can be offset to match the accompanying graph by replacing t with t - τ/2.