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.Este trabajo ha sido financiado por el Ministerio de Ciencia e Innovaci ón (Programa CONSOLIDER-INGENIO 2010) bajo los proyectos CSD2008-00066, EMET, y CSD2008-00068, Terasense, y por la Junta de Andalucía bajo el proyecto P10- TIC-6883
