Sub-THz Silicon-Micromachined Reconfigurable Beam-Steering Frontend

This paper presents a reconfigurable silicon micromachined beam-steering antenna frontend. The antenna frontend consists of multiple components that are integrated within a single chip with a total size of $14.3 \times 20 \times 1.2 \mathrm{~mm}^{3}$. The signal path includes a novel switching circuit for beam-shape switching, a magic-tee, a delay network for beam-steering, two power-dividing networks for sidelobe level (SLL) reduction, and a $2 \times 8$ antenna array. The implemented antenna frontend can radiate two frequency steerable beam-shapes, in which the switching circuit determines the radiated pattern. The first beam-shape is a broad beam, and the second is a notched beam. According to the required specifications, both radiation patterns can be steered by the operating frequency in the E-plane and move from −20 degrees at 238 GHz to +20 degrees at $\mathbf{2 4 8}~\mathrm{GHz}$. The SLL is reduced in the H-plane with the measured SLL of better than $18.5 \mathrm{~dB}$ for the broad beam in the entire sweeping range. The measured notch depth is better than $24 \mathrm{~dB}$ in the entire sweeping range. The measured return loss of the fabricated device is better than $15 \mathrm{~dB}$ between 220 and 265 GHz, which is equal to $18.6 \%$ of fractional bandwidth.