  The recent WMAP data represents a milestone in cosmology and helps constrain
cosmological parameters with unprecedented accuracy. In this work we combine
the WMAP data with previous CMB anisotropy measurements at smaller angular
scales to characterize the shape of the CMB anisotropy power spectrum. We carry
out a phenomenological analysis of the data. By allowing non-physical shapes of
the power spectrum we analyse high and low frequency experiments separately and
together. We find that WMAP dramatically constrains the power spectrum up to l
\~ 700. On smaller scales, the data show discrepancies that can be associated
with experimental systematics. If we combine all types of experiments, the
observable features in the power spectrum are in excellent agreement with the
WMAP cosmological parameter estimation. This work illustrates the advantages of
a model-independent approach to understanding experimental systematics that
might affect CMB observations.
