A 144-Element Beam-Steerable Source Array With 9.1-dBm Radiated Power and 30.8-dBm Lensless EIPR at 675 GHz

This article presents a large-scale coherent terahertz (THz) source array with 144 coupled oscillator elements. A novel 2-D scalable coupling topology suitable for large array formation is proposed to enable the desired coherent oscillation mode, in which a differential patch antenna can be incorporated, radiating the third harmonic for high output frequency beyond 600 GHz without a lens. High-efficiency harmonic oscillator design and optimization method are proposed for the third harmonic generation and extraction. This design is also capable of beam steering by changing the bias voltage to establish different phase gradients across the array. Finally, the fabricated chip can radiate 9.1-dBm power and 30.8-dBm lensless effective isotropic-radiated power (EIRP) at 675 GHz. The beam is steerable from - 45 ^{\circ} to 45 ^{\circ} in the H -plane, making it the highest power silicon-based THz source and highest frequency beam-steerable chip. This chip was fabricated in a 65-nm CMOS process, occupying a 2 \times 1.7 mm area. The output frequency is tunable from 643 to 689 GHz. At 675 GHz, the measured phase noise at 1-MHz offset is - 90.9 dBc/Hz, and the dc-to-THz efficiency is 0.245%.