Sequentially Fed Rhombus Patch Subarray for Wide-Angle Circularly Polarized Antenna-in-Package

Abstract

This paper presents a sequentially fed rhombus patch subarray for a wide-angle circularly polarized (CP) antenna-in-package in Ka-band low-Earth-orbit satellite communications. The proposed design approach is based on integrating a sequentially fed patch array, showing broadband and wide-angle CP performance, into a hexagonal lattice. Three rhombus patches are arranged with 120 degrees rotational symmetry, each aperture-coupled by a feeding network consisting of a three-way power divider and 120 degrees phase delay lines. This enables maximum radiation and CP property in the given hexagonal lattice. Moreover, due to the proximity effect between the tightly coupled patches, the antenna size can be reduced to 0.58 lambda(0) diameter (lambda(0) is a free-space wavelength at 28 GHz), while mitigating the mutual coupling effect on CP radiation by exciting a pair of patches simultaneously. The honeycomb-shaped array configuration enables symmetric beam scanning and maintains CP properties for wide-angle beamforming while preventing grating lobes. The proposed antenna is fabricated as a 4 x 4 array with dimensions of 2.2 lambda(0)x 2.7 lambda(0) and validated through measurement. The measured averaged matching bandwidth is 2.6 GHz (27.1-29.7 GHz), and port isolation is higher than 30 dB. The measured 3-dB axial ratio bandwidth is 1.2 GHz, with stable beamforming gains of 11.93 dBic, 12.27 dBic, and 8.72 dBic at theta(0) = 0 degrees , 15 degrees , and 30 degrees .