A True-Differential Attenuator With Phase Error Compensation for Low-Power Phased Array Systems

This letter presents a true-differential magnetically switchable coupled-lines (TD-MSCLs)-based attenuator with broadband phase compensation characteristics. The structure features low insertion loss (IL), compact size, low amplitude and phase errors, and intrinsic ESD protection. Compared to the MSCL structure, the TD-MSCL structure offers differential operation with common-mode (CM) rejection that is more suitable for terahertz ICs. In addition, it features phase compensation over a wide bandwidth by inducing proper coupling between two differential-mode (DM) MSCL cells. The attenuator prototype was implemented in a 0.13- $\mu $ m SiGe BiCMOS technology, exhibiting only 2.6-dB IL and <0.43 dB/5° rms amplitude/phase error within 200–230 GHz and 14-dB CM rejection ratio (CMRR) in a compact area of 0.019 mm2. To the best of our knowledge, it is the first true differential attenuator at 220 GHz and beyond.