For magnetoelectric antenna ,we put a magnetostrictive(MS) layer on piezoelectric layer to radiate electromagnetic wave. But i find that the piezoelectric layer can also radiate electromagnetic wave without MS layer and has a similar radiated power. What is the advantage for ME antenna compared with only piezoelectric antenna?
If you have a planar E antenna without a metal back, it will radiate symmetrically about the plane. So will a planar M antenna without a metal back. An EH antenna without a metal back will radiate unsymmetrically. A simple example of this is the difference between an elementary electric dipole, and elementary magnetic dipole, and a Huygens source, which combines both, with the same electric polarization in the forward direction. If you add a metal backing plane, none of the antennas can radiate backwards. There will be pattern differences off-normal because the null directions for an electric dipole and magnetic dipole, of the same electric polarizations, are in different directions.
I think that over a ground plane the ME antenna has no basic advantage but there may be some situations where it might be better to use.
an "ME" antenna is a Huygens source, which consists of an electrically-short electric dipole and an orthogonal short magnetic dipole. The combination then radiates in one direction only, like a Huygens source, when the M and E dipoles are excited in-phase. The magneto-strictive part is your magnetic dipole. The piezzoelectric part is the electric dipole, so you need both to make a Huygens source. Each dipole on its own is merely a short dipole which radiates in all directions (except along its axis).
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