Equation (
4.4) can be used to write down the spectral representation of

by inspection, as shown in Fig.
4.12. In the example
of Fig.
4.12, we have

Hz and

Hz,
where, as always,

. For comparison, the spectral
magnitude of an
unmodulated 
Hz
sinusoid is shown in
Fig.
4.6. Note in Fig.
4.12 how each of the two
sinusoidal components at

Hz have been ``split'' into two
``side bands'', one

Hz higher and the other

Hz lower, that
is,

. Note also how the
amplitude of the split component is divided equally among its
two side bands.

figure[htbp]
Recall that

was defined as the
second term of
Eq.

(
4.1). The first term is simply the original unmodulated
signal. Therefore, we have effectively been considering AM with a
``very large'' modulation index. In the more general case of
Eq.

(
4.1) with

given by Eq.

(
4.2), the magnitude of
the spectral representation appears as shown in Fig.
4.13.
figure[htbp]
Next Section: Bessel Functions