  We investigate the coherent mixing of co-propagating edge channels in a
quantum Hall bar produced by step potentials. In the case of two edge channels
it is found that, although a single step induces only a few percent mixing, a
series of steps could yield 50% mixing. In addition, a strong mixing is found
when the potential height of a single step allows a different number of edge
channels on the two sides of the step. Charge density probability has been also
calculated even for the case where the step is smoothened.
