reflectionless matching

I'm writing a program for simulating a 1D wave propagating across a boundary between two media using FDTD. I note that even though the refectionless matching condition is satisfied (e2=e1, nuy2=nuy1, e2/sigma=nuy2/sigma*), a large portion of wave is reflected backward. I think that the problem results from a spatial offset (a half of an unit cell) between E and H. Is it right? Could you help me to solve the problem?
Thank you very much.

use one-order Mur ABC