The present disclosure relates to a method for testing a device under test by using a test system. The method comprises the steps of: generating a wideband modulated signal; forwarding the wideband modulated signal to an input of a device under test; separating an electromagnetic wave reflected at the input by the directional element; forwarding the reflected electromagnetic wave to a test and measurement instrument; processing a reference signal associated with the wideband modulated signal; and determining a channel response by taking the reference signal and at least one scattering parameter of the device under test into account, wherein the scattering parameter depends on the reflected electromagnetic wave. Further, the present disclosure relates to a test system.