The analytic part of a signal f (t) is obtained by suppressing the neg
ative frequency content of f, or in other words, by suppressing the ne
gative portion of the Fourier transform, (f) over cap of f. In the tim
e domain, the construction of the analytic part is based on the Hilber
t transform (f) over cap of f(t), We generalize the definition of the
Hilbert transform in order to obtain the analytic part of a signal tha
t is associated with its fractional Fourier transform, i,e,, that part
of the signal f (t) that is obtained by suppressing the negative freq
uency content of the fractional Fourier transform of f (t), We also sh
ow that the generalized Hilbert transform has similar properties to th
ose of the ordinary Hilbert transform, but it lacks the semigroup prop
erty of the fractional Fourier transform.