35-GHz Wideband Circularly Polarized Patch Array on LTCC

Abstract

A 35-GHz wideband circularly polarized (CP) patch array of $2\times 2$ elements using low-temperature cofired ceramic technology is presented. The widened 3-dB axial ratio (AR) bandwidth is achieved by constructing a $1 \times 2$ sequentially rotated CP patch array with small inner-element spacing in the antenna element. The antenna element consists of two close circular patches with diagonal perturbations, and the patches are rotated with respect to each other. The two patches are fed with equal amplitude and orthogonal phase difference using one probe, which has one vertical part and two different horizontal parts. The fabricated array with a dimension of $15.3 \times 28.3\times 1.3$ mm3 shows wide −10-dB $\mid S_{11} \mid $ and 3-dB AR bandwidths of over 29.6% and 26%, respectively. The measured maximum gain of the four-element array is 9.3 dBi with slight fluctuations over 31–39 GHz frequency range.