  We study systematic effects from half-wave plates (HWPs) for cosmic microwave
background (CMB) experiments using full-sky time-domain beam convolution
simulations. Using an optical model for a fiducial spaceborne two-lens
refractor telescope, we investigate how different HWP configurations optimized
for dichroic detectors centred at 95 and 150 GHz impact the reconstruction of
primordial B-mode polarization. We pay particular attention to possible biases
arising from the interaction of frequency dependent HWP non-idealities with
polarized Galactic dust emission and the interaction between the HWP and the
instrumental beam. To produce these simulations, we have extended the
capabilities of the publicly available beamconv code. To our knowledge, we
produce the first time-domain simulations that include both HWP non-idealities
and realistic full-sky beam convolution. Our analysis shows how certain
achromatic HWP configurations produce significant systematic polarization angle
offsets that vary for sky components with different frequency dependence. Our
analysis also demonstrates that once we account for interactions with HWPs,
realistic beam models with non-negligible cross-polarization and sidelobes will
cause significant B-mode residuals that will have to be extensively modelled in
some cases.
