Recently, the authors introduced a novel planar radiating element that exploits the characteristics of the slotline microstrip coupling to obtain a microstrip-fed slot with broadband matching. This paper reviews the main characteristics of the so-called complementary strip-slot element and comments on its use for building series-fed planar arrays. In this way, two different configurations of series-fed arrays are described: a traveling-wave array of five elements and a circularly-polarized ring array with four elements. The scanning capabilities of the former, together with the multiband behaviour of the circularlypolarized array are highlighted.