Phased array using the sequential rotation principle: analysis of coupling effects

The growing demand for broadband multimedia services urges the aeronautical industry to provide bi-directional on-board communication services in near future. Today, the first aircrafts are already being equipped with the technology necessary to provide Internet access for staff and passengers. Up to now, these solutions are developed to operate in L- and Ku-band, due to the satellite systems available and the existence of affordable RF-components for these frequency ranges. Considering broadband multimedia applications, however, it is obvious that in the near future the technology will have to explore higher frequency regions like Ka-band, where the required bandwidth can be provided. Several studies show that, for airborne broadband satellite communications, the terminal antenna is one of the key components in the system design. To compensate for the aircrafts movement, the terminal antenna must be steerable, to allow satellite tracking. Due to the limitations of mechanically steerable antennas, an electronically steerable array antenna using digital beamforming seems to be the most promising solution. Still, the development of such antenna arrays in Ka-band technology faces high demands regarding performance, integration and, last but not least, component costs. In the framework of a project called SANTANA (smart antenna terminal), funded by the German government (BMBF) on behalf of the DLR, several antenna concepts have been investigated. One promising concept, which will be discussed in this paper, is a transmit-only array at 30 GHz that uses the sequential rotation principle to improve the circular polarisation.