SLA Printed Sub-Terahertz Bifilar Helix Antenna for Radar Imaging

The continuous improvement of additive stereo-lithographic manufacturing (SLA) allows to fabricate filigree sub-Terahertz antennas. This paper presents the first 3D-printed bifilar WR6 helix antenna, which depends on recent developments of printed transition from waveguides to bifilar helices. The measurements of the circularly polarized antenna indicate a $-15\mathrm{~dB}$ bandwidth of $B_{15\mathrm{~dB}}=10\mathrm{GHz}$. The axial ratio $AR$ is within $B_{15\mathrm{~dB}}\lt\mathbf{3 . 5}\mathrm{dB}$ in the main lobe direction. The achieved linear polarization gain is $G_{1p}14\mathrm{dBi}$ with a circular polarization gain of $G_{cp}11$ to 12 dBi. Due to its small form factor and circular polarization the proposed bifilar helical antenna is suitable for applications in the 120 GHz ISM band, i.e. polarimetric imaging and decomposition as well as broadband communication, e.g. 6G applications.