  We consider the extension of the supersymmetric Pati-Salam model which solves
the b-quark mass problem of supersymmetric grand unified models with exact
Yukawa unification and universal boundary conditions and leads to the so-called
new shifted hybrid inflationary scenario. We show that this model can also lead
to a new version of smooth hybrid inflation based only on renormalizable
interactions provided that a particular parameter of its superpotential is
somewhat small. The potential possesses valleys of minima with classical
inclination, which can be used as inflationary paths. The model is consistent
with the fitting of the three-year Wilkinson microwave anisotropy probe data by
the standard power-law cosmological model with cold dark matter and a
cosmological constant. In particular, the spectral index turns out to be
adequately small so that it is compatible with the data. Moreover, the
Pati-Salam gauge group is broken to the standard model gauge group during
inflation and, thus, no monopoles are formed at the end of inflation.
Supergravity corrections based on a non-minimal Kaehler potential with a
convenient choice of a sign keep the spectral index comfortably within the
allowed range without generating maxima and minima of the potential on the
inflationary path. So, unnatural restrictions on the initial conditions for
inflation can be avoided.
