  This paper presents an exact solution for a perfect conversion of a
TM-polarized surface wave (SW) into a TM-polarized leaky-wave (LW) using a
reciprocal and lossless penetrable metasurface (MTS) characterized by a scalar
sheet impedance, located on a grounded slab. In contrast to known realizations
of leaky-wave antennas, the optimal surface reactance modulation which is found
here ensures the absence of evanescent higher-order modes of the field
Floquet-wave expansion near the radiating surface. Thus, all the energy carried
by the surface wave is used for launching the single inhomogeneous plane wave
into space without accumulation of reactive energy in the higher-order modes.
It is shown that the resulting penetrable MTS exhibits variation from an
inductive to a capacitive reactance passing through a resonance. The present
formulation complements a previous paper of the authors in which a perfect
conversion from TM-polarized SW to TE-polarized LW was found for impenetrable
boundary conditions. Here, the solution takes into account the grounded slab
dispersion and it is convenient for practical implementation.
