  Studies of the three-dimensional (3D) structures of galactic magnetic fields
are now entering a new era, with broadband, highly sensitive radio observations
and new analysis methods. To reveal the magnetic field configuration from the
observed value integrated along the line of sight, it is necessary to derive an
appropriate model that can reproduce the observational characteristics. We aim
to clarify the relationship between the radiation field and the spatial
distribution of physical quantities through pseudo-observations using global 3D
magnetohydrodynamics (MHD) simulation results. In particular, we focus on using
the depolarization effect to verify the polarization model and to identify the
emission region. First, we show that wavelength-independent depolarization,
which takes into account anisotropic turbulence, does not work efficiently
because the polarized emission is stronger in regions of ordered spiral fields
than in regions dominated by isotropic turbulent fields. Beam depolarization
becomes more effective below 1 GHz. Although close to the equatorial plane
there will be strong depolarization which increases with observing wavelength,
this effect is less in the halo, making halo magnetic fields detectable through
their polarized emission at meter-wavelength bands. Although polarized emission
from the halo is below the detection limit of current facilities, it will be
detectable within the SKA era. In addition, we found that the spiral
polarization projected on a screen is produced by overlapping magnetic flux
tubes extending to different heights from the equatorial plane. This suggests
that the traditional classification of global magnetic fields has difficulty
reproducing the global structure of the magnetic fields. Finally, we
demonstrate the method to separate magnetic flux tubes at different heights by
using peak frequencies which cause the decreasing of polarized flux.
