Multiband circularly-polarized planar array based on the complementary strip-slot element

The concept of a circularly-polarized planar array based on the use of the complementary strip-slot element is explored. This element is a conventional microstrip-fed slot that overcomes its narrow bandwidth by using a strip superimposed onto it. The array is fed in a traveling-wave configuration and a ring shape is used to provide the required circular polarization with the sequential rotation technique. A design example is analysed by electromagnetic simulation. Thanks to the broadly-matched strip-slot element, multiband behaviour with axial ratio below 3 dB, good matching (better than 15 dB) and high radiation efficiency is obtained at 6.2, 8.9 and 12.3 GHz. This novel antenna offers design flexibility with a very simple structure.