  Angular power spectra and structure functions of the Stokes parameters Q and
U and polarized intensity P are derived from three sets of radio polarimetric
observations. Two of the observed fields have been studied at multiple
frequencies, allowing determination of power spectra and structure functions of
rotation measure RM as well. The third field extends over a large part of the
northern sky, so that the variation of the power spectra over Galactic latitude
and longitude can be studied. The power spectra of Q and U are steeper than
those of P, probably because a foreground Faraday screen creates extra
structure in Q and U, but not in P. The extra structure in Q and U occurs on
large scales, and therefore causes a steeper spectrum. The derived slope of the
power spectrum of P is the multipole spectral index, and is consistent with
earlier estimates. The multipole spectral index decreases with Galactic
latitude (i.e. the spectrum becomes flatter), but is consistent with a constant
value over Galactic longitude. Power spectra of the rotation measure RM show a
spectral index of about 1, while the structure function of RM is approximately
flat. The structure function is flatter than earlier estimates from polarized
extragalactic sources, which could be due to the fact that extragalactic source
RM probes the complete line of sight through the Galaxy, whereas as a result of
depolarization diffuse radio polarization only probes the nearby ISM.
