  We investigate systematically the quark-hadron mixed phase in dense stellar
matter, and its influence on compact star structures. The properties of quark
matter and hadronic matter are fixed based on various model predictions. Beside
adopting constant values, the surface tension $\Sigma$ for the quark-hadron
interface is estimated with the multiple reflection expansion method and
equivparticle model. To fix the structures of quark-hadron pasta phases, a
continuous dimensionality of the structure is adopted as proposed by Ravenhall,
Pethick, and Wilson. The corresponding properties of hybrid stars are then
obtained and confronted with pulsar observations. It is found that the
correlation between radius and tidal deformability in traditional neutron stars
preserves in hybrid stars. For those permitted by pulsar observations, in
almost all cases the quark phase persists inside the most massive compact
stars. The quark-hadron interface plays an important role on hybrid star
structures once quark matter emerges. The surface tension $\Sigma$ estimated
with various methods increases with density, which predicts stiffer EOSs for
the quark-hadron mixed phase and increases the maximum mass of hybrid stars.
The EOSs of hybrid star matter are well constrained at densities $n\lesssim
0.8$ fm${}^{-3}$, while larger uncertainty is expected at higher densities.
