Experimental performance comparison of two polarimeter techniques for CMB applications

Polarisation modulators are necessary for present and next generations of CMB polarisation experiments. Because of the very faint B-mode signal expected, these instruments have not only to be extremely sensitive but also to have low and well-characterised systematic effects. The beam RF characterisation in the W-band (75-110 GHz) of two polarimeter pixels using the same corrugated horn has been performed using two different modulators: a waveguide rotator modulator and a quasi-optical half-wave plate. Co- and cross-polarisation beam measurements are presented together with the systematic effects introduced by both modulators.