A Wideband Scanning Circularly Polarized Array Antenna Based on the Shorted Transmission Line Model

Due to the huge potential of application in the communications, electronic jamming, and radar fields, circularly polarized (CP) array antennas with wide axial ratio (AR) scanning performance at wide frequency bandwidth have received great attention. A wideband scanning CP planar array antenna built by new, tightly coupled dipole array (CP-TCDA) elements, which have achieved promising results in terms of both scanning AR bandwidth and angle range in all scanning planes, is presented in this paper. Based on the shorted transmission line model, a CP-TCDA element arranged along the ±45° direction is constructed, which can shift the middle-frequency scanning blind zone out of band and thus obtain a wideband scanning AR bandwidth. Furthermore, the proposed CP-TCDA element adopts four shorting pins and four square parasitic strips, which improve wide-angle CP performance for
xz
-plane and diagonal-plane scans, respectively. An
$8\times 8$
left-handed CP planar array antenna based on the proposed CP-TCDA elements is designed and prototyped. The results show that the array antenna is able to operate over a 3:1 (4–12 GHz) overlapping bandwidth, and it meets the requirements of AR < 3 dB and active VSWR < 2.9 within a ±45° scanning angle range.