"Richard Fry" wrote in message
...
Why would varying the pulse width without changing the characteristics of
the pulse transitions (rise/fall) affect the harmonic content of the
pulse?
No bandwidth and no harmonics at all are produced by the constant DC level
of the pulse before and after each transition.

Wouldn't the harmonic structure and bandwidth needed to produce/reproduce
a
pulse be related only to the rise and fall times of that pulse, and the
transition shapes (sin^2, etc), and be independent of the width (time)
between the transitions?
============================

The shape of the pulse, the width of the pulse, the time interval between
pulses, all affect the harmonic frequency spectrum. They act both
independently and in conjunction with each other.

The best way to grasp what happens is to calculate the amplitudes of the
series of harmonics which result from several different shaped pulses, of
different pulse widths, spaced at different intervals.

In particular, you will find that varying the ratio of pulse width to
spacing results in some of the harmonics virtually disappearing in
amplitude.

You can also graphically reconstruct pulses and waveshapes but excluding
harmonics beyond the N'th to see what happens.

You will need a good book which gives the amplitudes and phases of the
harmonic sinewave terms in the infinite series of a selection pulse shapes.

Or you can construct a harmonic generator and examine its output with a
spectrum analyser.

Fascinating if you have the time to spare.