Ultrawideband Conformal Transmitarray Employing Connected Slot-Bowtie Elements

In contrast to using multi-layer frequency selective surface (FSS) elements or tightly coupled elements, a novel technique is introduced here to achieve ultrawideband planar and conformal transmitarrays, which are based on connected elements like those used in connected arrays. In particular, the elements consist of a horizontally connected slot-bowtie and vertical meander slot-lines. The elements are capable of achieving a 360° phase variation range at the highest frequency 17 GHz with the transmission loss less than 3 dB from 6 GHz to 17 GHz. The transmitarrays have been designed, fabricated and measured in both planar and conformal versions. Stable boresight radiation patterns from 6 GHz to 17 GHz have been obtained for both antennas. Compared to conformal transmitarrays using multi-layer FSS elements, the proposed solution has a much wider bandwidth of radiation patterns. Good agreement has been found between simulation and measurement.