  The scattering of surface plasmons polaritons by a one-dimensional defect of
the surface is theoretically studied, by means of both Rayleigh and modal
expansions. The considered defects are either relief perturbations or
variations in the permittivity of the metal. The dependence of transmission,
reflection and out-of-plane scattering on parameters defining the defect is
presented. We find that the radiated energy is forwardly directed (with respect
to the surface plasmon propagation) in the case of an impedance defect.
However, for relief defects, the radiated energy may be directed into backward
or forward (or both) directions, depending on the defect width.
