  We have analyzed the polarization properties of pulsars at an observing
frequency of 4.9 GHz. Together with low frequency data, we are able to trace
polarization profiles over more than three octaves into an interesting
frequency regime. At those high frequencies the polarization properties often
undergo important changes such as significant depolarization. A detailed
analysis allowed us to identify parameters, which regulate those changes. A
significant correlation was found between the integrated degree of polarization
and the loss of rotational energy E^dot. The data were also used to review the
widely established pulsar profile classification scheme of core- and cone-type
beams. We have discovered the existence of pulsars which show a strongly
increasing degree of circular polarization towards high frequencies. Previously
unpublished average polarization profiles, recorded at the 100m Effelsberg
radio telescope, are presented for 32 radio pulsars at 4.9 GHz. The data were
used to derive polarimetric parameters and emission heights.
