Broadband Circularly Polarized Stacked Antenna with Sequential-Phase Feed Technique

A broadband circularly polarised (CP) stacked antenna with a sequential-phase feed technique is proposed in this study. The antenna contains a square ring that is encircled by four driven patches. The gap-coupled feed method is used to transfer energy from the square ring to the driven patches. Moreover, four stacked patches are placed above the bottom layer to enhance the impedance and CP bandwidths. The measured results yield an impedance bandwidth of 33.6% (4.78–6.71 GHz) and a wide 3 dB axial ratio bandwidth of 19.4% (4.90–5.95 GHz) is obtained. The average gain is ∼9 dBi and the variation of gain is <1 dB within the CP bandwidth.