Summary: To determine the transmission bandwidth of certain signal sets, consider the baseband version.

What is the transmission bandwidth of these signal sets? We
need only consider the baseband version as the second is an
amplitude-modulated version of the first. The bandwidth is
determined by the bit sequence. If the bit sequence is constant
— always 0 or always 1 — the transmitted signal is a
constant, which has zero bandwidth. The
worst-case—bandwidth consuming—bit sequence is the
alternating one shown in Figure 1. In this case, the transmitted signal is a square
wave having a period of

From our work in Fourier series, we know that this signal's
spectrum contains odd-harmonics of the fundamental, which here
equals

Show that indeed the first and third harmonics contain 90%
of the transmitted power. If the receiver uses a front-end
filter of bandwidth

The harmonic distortion is 10%.

What is the 90% transmission bandwidth of the modulated signal set?

Twice the baseband bandwidth because both positive and
negative frequencies are shifted to the carrier by the
modulation: