  Coherent curvature radiation as the radiation mechanism for fast radio bursts
(FRBs) has been discussed since FRBs were discovered. We study the spectral and
polarization properties of repeating FRBs within the framework of coherent
curvature radiation by charged bunches in the magnetosphere of a highly
magnetized neutron star. The spectra can be generally characterized by
multisegment broken power laws, and evolve as bunches move and the line of
sight sweeps. Emitted waves are highly linear polarized if the line of sight is
confined to the beam within an angle of $1/\gamma$, while circular polarized
degree becomes strong for off-beam cases. The spectro-temporal pulse-to-pulse
properties can be a natural consequence due to the magnetospheric geometry. We
investigate the relationship between drift rate, central frequency and their
temporal duration. The radius-to-frequency mapping is derived and simulated
within the assumptions of both dipolar and quadrupolar magnetic configurations.
The geometric results show that FRBs are emitted in field lines more curved
than open field lines for a dipolar geometry. This suggests that there are most
likely existing multipolar magnetic configurations in the emission region.
