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

In this paper, a low-temperature co-fired ceramic (LTCC)-based E-shaped planar in-verted-F antenna (PIFA) is proposed for circularly polarized (CP) at D-band (110-170GHz). For stable CP radiation characteristic, a densified self-sequential rotation feeding (DSRF) 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 (HOM) substrate integrated waveguide (SIW) 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 (THz) CP antenna array designs.