Bandwidth- and Gain-Enhanced Circularly Polarized Antenna Array Using Sequential Phase Feed

A technique is developed in this letter to enhance the impedance and axial-ratio (AR) bandwidths as well as broadside gain of a sequential phase (SP) feed 2 × 2 patch array. The proposed antenna is composed of a probe-fed patch, a 2 × 2 corner truncated patch array with a loop, and a slotted metal wall surrounding the feeding structure. The proposed antenna combines the attractive features such as wide impedance and AR bandwidths, low profile, and easiness of design and manufacture. The antenna operating at 5-GHz band is designed and fabricated with overall volume of 1.5 λ0×1.5 λ0×0.06 λ0. Measured results show that the antenna array achieves an impedance bandwidth of about 20.8% for |S11|<;-10 dB, a 3-dB AR bandwidth of about 17.6%, a peak gain of 11.5 dBi, and a 3-dB gain bandwidth of 13%, which is completely within the impedance and AR bandwidths.