SIW pillbox antenna with integrated beam-switching feeds for mutual coupling reduction between close-spaced sources

The beam overlapping level between adjacent beams is a very important factor in order to obtain an efficient coverage of the beam-scanning range using electrically switched multi-beam antennas. Typically, a -3 dB beam-crossing level is desired. In a reflector system, this can be achieved by reducing the interspace distance between consecutive sources. By reducing the distance between adjacent feeds and eventually their size, the mutual coupling between them increases. Typically, a high level of mutual coupling can reduce the directivity of the sources, affecting the efficiency of the whole antenna system (Llombart et al., IEEE Trans. Antennas Propag., 56, 4, 1201-1206, 2008). Besides, in pillbox systems, the parabola taper and overall losses also increase.