  The high frequency vortex motion in Nb$_3$Sn was analyzed in this work up to
12 T. We used a dielectric loaded resonator tuned at 15 GHz to evaluate the
surface impedance $Z$ of a Nb$_3$Sn bulk sample (24.8 at.\%Sn). From the field
induced variation of $Z$, the high frequency vortex parameters (the pinning
constant $k_p$, the depinning frequency $\nu_p$ and the flux flow resistivity
$\rho_{ff}$) were obtained over a large temperature and field range; their
field and temperature dependence were analyzed. Comparison with other
superconducting materials shows that high frequency applications in strong
magnetic fields are also feasible with Nb$_3$Sn. In the present work, we report
the first measurements about the microwave response in Nb$_3$Sn in strong
magnetic fields.
