LAUSR

In this article, a highly efficient terahertz (THz) beam-steerable integrated radiator based on tunable boundary conditions is presented. The boundary conditions seen by the central slot radiator are tuned by the switched slots, and the corresponding radiation patterns can be altered. This technique enables a beam-steerable THz antenna with high radiation efficiency. In addition, the DC-THz efficiency of the harmonic voltage-control oscillator (VCO) is boosted through the 2-D harmonic boosting technique. Based on the two techniques above, the THz beam-steerable radiator has been implemented in a 130-nm SiGe BiCMOS process ( $f_{T}/f_{\mathrm {max}} =300$ /450 GHz). Without silicon lens, it achieves 60° scan ranges in the $E$ -plane, an equivalent isotropic radiated power (EIRP) of 2.2 dBm, −2.8 dBm radiation power, 0.91% DC-THz efficiency, and the tuning range of 11.5% for the supply of 1.7 V. With silicon lens, it achieves the EIRP of 21.66 dBm, 0.56-dBm radiation power, 2.22% DC-THz efficiency, and tuning range of 10.8% for the supply of 1.6 V. Among the silicon-based beam-steerable radiators over 300 GHz, it achieves state-of-the-art dc-to-THz efficiency.