Factors affecting signal bandwidth (cont.)

Not only is the shape of the waveform important in determining the amplitude of the frequency components within the Fourier series expansion, but the width of the data pulses also plays an important role.

As can be seen here, reducing the width of the pulse but keeping the period of the waveform constant results in an increase in the level of the higher harmonics at the expense of the lower harmonic levels. Overall, the energy content in the waveform has also gone down and so the combined power of the harmonics must also be reduced.

In the limit, as the pulse width tends to zero, that is, a delta function, we can expect the amplitude of each harmonic to approach a constant yet diminishing value.