A broadband single-fed circularly polarized patch filtenna with high suppression level

In this manuscript, a single-fed circularly polarized patch antenna is presented, which features a large bandwidth and a high out-of-band suppression level, simultaneously. By loading a stacked patch and etching U-shaped slots on the driven and stacked patches respectively, a high out-of-band suppression level can be obtained without any extra filtering circuits. Furtherly, to widen the bandwidth of the filtering CP patch, two T-shaped slots and a stepped via-line-via feeding structure are introduced. Finally, for demonstration, a prototype was fabricated and measured. The measurements indicated a large impedance bandwidth of 35.7%, an axial-ratio bandwidth of 10.8%, a peak gain of 8.5 dBic, and a high out-of-band suppression level of up to 28.5 dB in stopbands.