A Fully Integrated 263-GHz Retro-Backscatter Circuit with 105°/82° Reading Angle and 12-dB Conversion Loss

This paper presents the first fully integrated on-chip sub-THz retro-backscatter CMOS circuit, operating at 263 GHz. Using the Van Atta reflector principle and a signal swapping and mode-conversion electromagnetic structure, the design achieves retro-directive operation with a 3-dB angle availability of $105^{\circ} / 82^{\circ}$. Fabricated in an Intel-16 CMOS process, the prototype demonstrates BPSK modulation over an input power range of -7 dBm to -13.9 dBm at 263 GHz, exhibiting a measured conversion loss of $\mathbf{1 2}$ dB and capability of Mbps-level data rate at $5-\mathrm{cm}$ reader-to-chip distance. These findings validate a low-cost, low-power, wide-angle THz retro-backscatter solution, improving the performance and practicality of ultra-miniaturized tag applications.