Design of SIW-Fed End-fire Exponential Tapered Horn Antenna for sub-THz Communications

High gain and broadband antennas are crucial to meet the demand for efficient high-speed communication in sub-terahertz (Sub-THz) frequencies. Achieving both simultaneously is typically challenging for planar antennas in this frequency band. This letter proposes a low-profile substrate integrated waveguide (SIW) fed end-fire exponential tapered horn antenna (ETHA) designed and analyzed for sub-THz communications. To mitigate the impedance mismatch caused by the thin substrate (0.254 lambda(0)), a semi-open SIW horn is designed by exponentially detaching one broadwall in the flare part while retaining the other. Additionally, to improve the radiation performances, a dielectric slab is added to the aperture of the horn to facilitate a smooth transition to free space. The antenna element operates within the frequency band from 220- 328.68 GHz, providing a -10 dB fractional impedance bandwidth of 39.6% centered at 274 GHz. With stable endfire radiation patterns, the antenna achieves a peak realized gain of 15.5 dBi at the center frequency with 3 dB beamwidth of 11.6 degrees in the H-plane and 18.1 degrees in the E-plane. These outcomes make this antenna highly promising for operation within channel 69, as defined by the IEEE 802.15.3d standard.