A 0.47-THz Ring Scalable Coupled Oscillator–Radiator Array With Miniature Patch Antennas

This article integrates several techniques for largescale, high power-efficiency, and area-efficiency terahertz (THz)radiators. First, we present a systematic design method to synthesize a high output power harmonic oscillator at a high fundamental to maximum oscillation frequency (f_osc/f_max) ratio by making a quantitative tradeoff between fundamental oscillation and harmonic output power. Then, a ring scalable coupled oscillator array topology is proposed for a flexible and compact layout. Patch antennas are preferred for large-scale radiator arrays, but the size is much larger than the commonly used slot antenna. Therefore, a miniature on-chip patch antenna is proposed for front-side radiation, whose compact size also helps make the design scalable in 2-D. A quartz superstrate is superimposed on the chip to improve the radiation efficiency. A 16-element ring-coupled oscillator–radiator array is designed and fabricated in a 0.8-mm² total area using a 65-nm CMOS process to verify the design methods. Maximum radiated power of −2.8 dBm is measured at 472 GHz. This design achieves an area efficiency of 0.66 mW/mm², the highest among THz radiator arrays using on-chip patch antennas. It is even higher than most radiator arrays using slot antennas. This design also achieves the state-of-the-art dc-to-THz efficiency and frequency tuning range of 0.12% and 4.2%, respectively. The chip can be easily configured to feed a low-cost Teflon lens. A maximum effective isotropic radiated power (EIRP) of ∼30 dBm is measured with a 12-mm diameter lens. The measured directivity is 33.7 dBi. At 472 GHz, the measured phase noise is −71.3 dBc/Hz at the1-MHz offset.