A broadband substrate/feed design for conformal slot arrays

Conformal slot arrays have been widely used in mobile communication systems due to their distinctive features such as compactness, ease of fabrication, high power handling, frequency-scanning capability and wideband/wide-scanning performance. So far, the focus has been on waveguide-fed slot arrays. On the other hand, cavity-backed slot (CBS) arrays have also been considered mainly because of their low-profile, flush-mountable features. Nevertheless, the bandwidth of CBS antennas has been very limited except for the traveling-wave slot configurations. Here, our goal is to achieve bandwidth enhancement for cavity-backed planar slot arrays by introducing a novel substrate/feed design. When conformal slots are placed over cavity-backed, planar or curved substrates, their bandwidth and radiation characteristics are altered due to the presence of undesired modes (surface-wave or parallel-plate modes) within the cavity. Hence, it is essential to use a frequency-dependent substrate to improve antenna performance. This can be achieved by using a multilayer frequency selective surface as an artificial substrate with a tailored frequency response.