Gain-Improved Broadband Circularly Polarized Antenna Array With Parasitic Patches

A broadband circularly polarized (CP) antenna array with improved gain is proposed. The antenna consists of a CP loop that provides sequential phase, a 2 × 2 patch array, and four parasitic rectangular elements. The square patches are capacitively coupled with four strips, which are connected to the loop feeding network. Moreover, four parasitic rectangular patches are introduced to enhance the gain in the lower band. The measured 10-dB impedance bandwidth is 15.9% (5.01-5.87 GHz), and the 3-dB axial-ratio bandwidth of 640 MHz (5.08-5.72 GHz) is also obtained. Besides, the proposed antenna array has a flat gain over the operating frequency and the maximum gain of 12.5 dBi is achieved at 5.3 GHz.