Slot-Coupled Circularly Polarized Array Antenna With Substrate-Integrated Waveguide Cavity for Parallel-Plate-Mode Suppression

A slot-coupled circularly polarized (CP) patch antenna with parallel-plate-mode (PPM) suppression for phased array systems is presented in this paper. The radiation performances of the CP array antenna with PPM suppression are improved using a substrate-integrated waveguide (SIW) cavity. In order to obtain a high isolation between the feeds of a feeding circuit, the cavity size and locations of the feeds are attentively designed. In addition, the performances of the proposed array antenna are thoroughly investigated. A comparative study between antennas (with and without the SIW cavity) is presented, involving both simulation and measurement. The proposed antenna with the SIW cavity has a 17-dB lower mutual-coupling level compared with the antennas without the SIW cavity; the individual antennas in the array, therefore, present more consistent and reliable characteristics in terms of impedance and radiation performances. The beam scanning performance of an 8 x 8 phased CP array system is experimentally validated, and shown to exhibit the expected improvements in terms of gain, cross-polarization level, and axial ratio. The obtained results clearly demonstrate the advantages of the proposed antenna for CP phased array systems.