An LTCC-Based Antenna Array With Densified Self-Sequential Rotation Feeding Configuration for Circularly Polarized Terahertz Communications

In this article, a low-temperature cofired ceramic-based E-shaped planar inverted-F antenna is proposed for circularly polarized (CP) at D-band (110—170 GHz). For stable CP radiation characteristic, a densified self-sequential rotation feeding technique is applied for 2 × 2 subarray. Certain perturbance of field distribution is achieved by arranging the coupling feed disks properly. Hence, a TE₄₁₀-mode/quasi-TE₃₃₀ high-order-mode substrate integrated waveguide cavity is excited with four coupling feeding slots properly arranged to obtain equal amplitudes and sequential 90°-phase shifts, which can be deemed as high-order-mode-based densified self-sequential rotation feeding (HOM-DSRF) configuration. Thanks to the proposed HOM-DSRF configuration, the overall dimension of the 2 × 2 CP subarray is only 1.05λ × 1.05λ with a simulated aperture efficiency up to 96%, which is significantly superior to conventional sequentially rotation feeding methods in terms of overall dimension and aperture efficiency. Finally, a 4 × 4 antenna array is designed, fabricated, and measured. The measured impedance bandwidth and 3-dB axial ratio bandwidth are 10.4% from 145.7 to 161.7 GHz and 10.5% from 144 to 160 GHz, respectively. The measured peak gain is 15.1 dBic, with measured aperture efficiency up to 71%. The measured results agree well with the simulated ones. The proposed HOM-DSRF configuration has potential applications for terahertz CP antenna array designs.