A thorough analytical study is conducted of linear mode conversion near lower hybrid resonance in a one-dimensional weakly inhomogeneous plasma. The analysis is based on the cold-, warm- and hot-plasma approximations depending on the ratio of the ion Larmor radius to the perpendicular wavelength. Mode conversion is found to take place in two different locations. An appropriate differential equation is derived to describe the electric field in each of the mode conversion regions. A complete conversion of a long wavelength mode to a short wavelength mode is confirmed in both regions. The energy coupled into the plasma and the surface impedance of the plasma are computed for slow-wave excitations.