Mushroom-typed artificial magnetic surface(AMS) with double periodicity is proposed, measurements of surface wave show multi-band structures and dips in spectra both for TE and TM mode, which are in good agreement with FDTD simulation of surface wave and reflected phase spectra. Radiation patterns for a small dipole parallel to the surface are measured at different positions on the AMS. Forward radiation patterns in far field are enhanced within the surface band-gaps, which also are the regions of in phase, while backward radiation patterns are. suppressed effectively. Deep return loss corresponding to those frequencies with in phase reflection shows that the dipole work very well. At some frequencies, directivity can be observed, this may be due to the in phase reflection and out phase reflection inherited by this doubly periodic AMS.
