A Circularly Polarized Strip Dipole Antenna Array With Working Bandwidth Above 40% for Wireless and Satellite Communications

A broadband circularly polarized (CP) strip dipole antenna array is proposed in this letter. The basic structure is a Z-shaped dipole excited by a rectangular slot. CP radiation with a narrow axial ratio (AR) bandwidth is realized at the high-frequency band first. To widen bandwidth, a pair of transverse stubs are arranged at the beginnings of the Z-shaped dipole, which greatly increases the phase difference of two orthogonal electric fields and produces one new AR minimum point at the low-frequency band. Furthermore, two short vertical stubs are connected to the Z-shaped dipole, which can control the AR minimum point of high frequency. Hence, a wide AR bandwidth can be realized by manipulating two AR minimum points separately. To achieve good impedance matching and minimize the impact on AR, two vertical slots are incorporated into the rectangular coupling slot. Finally, the proposed CP strip dipole obtains an operating bandwidth of 46
${\rm{\% }}$
(19.1–30.5 GHz). Then, the single antenna is expanded into an antenna array with 64 elements to obtain high gain. The experimental results of the proposed array reveal an impedance bandwidth of 58
${\rm{\% }}$
(17.6–32 GHz) and an AR bandwidth of 42.8
${\rm{\% }}$
(19.25–29.75 GHz). The peak gain is 22.18 dBic. The experimental results verify good performance of the designed array.