Design Aspects of Single-Ended and Differential SiGe Low-Noise Amplifiers Operating Above f_max/2in Sub-THz/THz Frequencies

Abstract

This article presents a single-stage single-ended (SE) and a multistage pseudo-differential cascode low-noise amplifiers (D-LNA) with their center frequencies at 235 and 290 GHz, respectively. Both low-noise amplifiers (LNAs) are designed beyond half of the maximum frequency of oscillation ( f max ) in 130-nm SiGe BiCMOS technology with f t / f max of 300/450 GHz. Implications of gain-boosting and noise reduction techniques in cascode structure are analyzed and it is observed that beyond f max /2, these techniques do not provide desired benefits. The single-stage SE LNA is designed to ascertain the theoretical analysis, and the same analysis is further implemented in staggered tuned four-stage LNA. Single-stage SE LNA provides a small signal gain of 7.8 dB at 235 GHz with 50 GHz of 3-dB bandwidth by consuming 18 mW of power. Four-stage differential LNA gives 12.9 dB of gain at center frequency 290 GHz and 11.2 dB at 300 GHz by drawing 68 mA current from the 2-V supply. The 3-dB bandwidth of differential LNA is measured to be 23 GHz. Noise figure measurements of both LNAs are performed using a gain-method technique with their measured noise figure values of 11 and 16 dB, respectively. This work successfully demonstrates the possibility of using a Si-based process to implement amplifiers beyond f max /2. To the authors' best knowledge, the four-stage differential LNA achieves, without any gain-boosting technique, the highest gain at 2/3( f max ) with decent noise figure performance in SiGe technology.Index Terms-High current model (HICUM), low-noise amplifiers (LNAs), maximum frequency of oscillation ( f max ), receivers, SiGe BiCMOS integrated circuits, sub-THz and THz integrated circuits, vertical bipolar intercompany model (VBIC). I. INTRODUCTION F UTURE high-speed wireless technologies are dependent on the sub-THz and THz band of electromagnetic spectrum [1], [2], [3], [4]. In this aspect, IEEE 802.15.3d-2017 proposes the use of a sub-THz frequency range for point-to-point communication for data rates up to 100 Gb/s [5]. RF frontend design in the WR3.4 waveguide band (220-330 GHz) is very promising for future high-speed communication [6]. It has Manuscript