In this letter,we present a concentric annular-ring microstrip
antenna that covers the bands of Galileo (E5a, E5b, E1, E2,
L1), GPS (L1, L2, L5), and GLONASS (L1, L3). This microstrip
antenna is fed by four apertures that improve the coupling. Broadband
phase shifters and Wilkinson power combiners are used to
generate the required circular polarization.
Ramirez, M. [et al.]. Concentric annular-ring microstrip antenna with circular polarization. "IEEE antennas and wireless propagation letters", 2011, vol. 10, p. 517-519.