In continuous time, a periodic signal , with period
seconds,^{B.2} may be expanded
into a Fourier series with coefficients given by

(B.5)

where
is the th harmonic frequency
(rad/sec). The generally complex value
is called the
th Fourier series coefficient. The normalization by
is optional, but often included to make the Fourier series
coefficients independent of the fundamental frequency , and
thereby depend only on the shape of one period of the time
waveform.