  We model s- and d-wave ceramic superconductors with a three-dimensional
lattice of randomly distributed Josephson junctions with finite
self-inductance. The field and temperature dependences of the microwave
absoption are obtained by solving the corresponding Langevin dynamical
equations. We find that at magnetic field H=0 the microwave absoption of the
s-wave samples, when plotted against the field, has a minimum at any
temperature. In the case of d-wave superconductors one has a peak at H=0 in the
temperature region where the paramagnetic Meissner effect is observable. These
results agree with experiments. The dependence of the microwave absorption on
the screening strength was found to be nontrivial due to the crossover from the
weak to the strong screening regime.
