Lens antenna adjustment for telecommunication and imaging modes in a sub-THz radio system

This article presents a concept of a dual-mode operated sub-THz frequency radio system by adjusting the lens-antenna distance for either telecommunication or imaging modes. The signal transmittance and imaging capabilities are demonstrated using a continuous wave operated transceiver with operation frequency 220 to 330 GHz where the 6G wireless radio system could be allocated. A high-gain bullet-shape lens antenna was investigated for imaging the natural object (Bergenia leaf) in the short-range line-of-sight radio link. The bullet lens performed with the gain of 28 dB and the 1° beamwidth over the frequency band. For the demonstration of dual-mode operation, the leaf was placed into the middle of the radio link path and then its image was synthesized at three lenses to the antenna-distances by utilizing the inverse synthetic-aperture radar technique. For image synthesizing, the movement pattern area (100 mm × 100 mm) is defined with 5 mm steps to sweep the object area. Three 100 mm × 100 mm images by 5 mm steps from different lens positions in focal axis distances (4, 15, and 30 mm were synthesized. The comparison shows that 15 mm distance has the highest gain and 30 mm distance has the higher image quality. Therefore, there is the possibility to switch from the high gain low-resolution mode to the low gain high-resolution mode by changing the lens position in terms of the feed. The imaging feasibility can be applied at 6G radio systems if adjustable lens systems are used revealing the new potential features in future radios.