  A technique to derive the propagation characteristics and field distributions
of waves guided by scalar and tensorial reactance surfaces modulated by
periodic or discrete Fourier spectrum functions in the propagation direction is
presented. The method, based on an equivalent lumped circuits approach, can be
seen as a generalization of the Oliner method for the TM propagation on scalar
sinusoidally modulated reactance surfaces. Numerical results are obtained for
both surface wave and leaky wave solutions. The relevance of these studies to
modulated metasurface antennas is discussed.
