Concentric Annular-Ring Microstrip Antenna With Circular Polarization

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. Broad band phase shifters and Wilkinson power combiners are used to generate the required circular polarization.