The polarization properties of extragalactic radio sources at frequencies
higher than 20 GHz are still poorly constrained. However, their
characterization would provide invaluable information about the physics of the
emission processes and is crucial to estimate their contamination as
foregrounds of the polarized cosmic microwave background (CMB) angular power
spectrum on scales < 30 arcmin. In this contribution, after summarizing the
state-of-the-art of polarimetric observations in the millimetric wavelength
bands, we present our observations of a complete sample of 53 sources with S >
200 mJy (at 20 GHz) carried out with the Australia Telescope Compact Array
between 5.5 and 38 GHz. The analysis clearly shows that polarization properties
cannot be simply inferred from total intensity ones, as the spectral behaviors
of the two signals are typically different
