Numerical study of undercut cavity under triplate array element

The parallel plate mode (PPM) is a major loss mechanism within triplate arr ays, and placing a cavity under each array element is a means of suppressin g PPM. A numerical investigation as to the effect of extending the lateral dimensions of the cavity backing a single triplate element using Ansoft HFS S version 6 is presented. The directivity and radiation efficiency of the r adiating element have been found to vary with the lateral extension of the cavity. The optimal cavity lateral size in terms of radiation efficiency an d directivity are identified for two cavity depths.