A 299–315-GHz Dual-Band Radiator Array With Cascaded Transmission Line-Based Feedback Network for Phase Noise Improvement

Abstract

This paper presents a THz radiator array integrating two elements, each of which consists of two fundamental oscillators operating at half of the output frequency, a push-push frequency doubler and an on- chip square-shaped loop antenna. To improve the phase noise for the fundamental oscillators, a feedback network containing a long cascaded transmission line featuring high frequency selectivity is proposed. Then, the signal power is extracted through the use of a compact coupled line to drive the doubler, thereby making the integration of a multi-element array more manageable. Furthermore, the strength of the coupling between the two adjacent oscillators within each element is designed properly, yielding dual-band operation to extend the frequency range. Fabricated in a 65-nm bulk CMOS process, the radiator chip assembled with a crystal slab and a silicon lens achieves output frequency ranging from 299.2 to 314.8 GHz. The measured peak effective isotropically radiated power (EIRP) and radiated power are 3.9 and −16.1 dBm, respectively, while consuming 93-mW DC power from a 1.4-V power supply. The phase noise measures −79.9 dBc/Hz at 1-MHz offset from 312 GHz, corresponding to a figure-of-merit (FoM) of 170.1 dBc/Hz. The core area of the chip is $0.65\times 0.21$ mm2, excluding the pads.