Low-Noise Amplifiers and Phase Shifters in SiGe BiCMOS for D-Band RX Front-Ends

The ever-increasing demand for faster data transfer-rate and higher device density in mobile applications is posing severe requirements to the network infrastructure for 5G and beyond networks. Concurrently, radar imaging is a trending topic, mainly driven by assisted/autonomous driving and gesture recognition applications. Both wireless communication and remote sensing are going towards millimeter-waves and sub-THz bands, where unlicensed portions of the electromagnetic spectrum are largely available and wide bandwidth is easily accessible. Within this framework, BiCMOS is a promising technology, offering both high-speed high-power HBTs and CMOS nodes, enabling the possibility to realize complex systems on chip capable of going directly from the digital domain to the air and vice-versa. Nonetheless, today’s available nodes still suffer from a maximum oscillation frequency which is only twice or three times the operating frequency; this mandates a careful selection of circuits configurations and, possibly, the investigation of unconventional design solutions to get the most out of the technology. Phased-arrays have the benefit of increasing the total radiated power through beamforming and over-the-air-power combining, thus going beyond the power capability of a single-transistor transmitter, which is very limited compared to the one achieved in III-V technologies. On the receiver side, instead, they combine multiple channels giving a signal-to-noise ratio increase, thus enhancing the system sensitivity. For this reason, arrays with thousands of antennas are likely to become popular in the next future, and a high integration is required to make these systems affordable and reliable. Moreover, phased-arrays also open to the possibility of beam-steering, increasing the flexibility of point-to-point radio links. This thesis focuses on D-band (110 - 175GHz) building blocks for a receiver front-end. A description of transmission-line-based broadband matching networks is proposed to gain some insights about their working principle and it is applied to the design of high-frequency wideband amplifiers. A test chip demonstrates a LNA with 50% fractional bandwidth in D-band and state-of-the-art noise figure. A discussion on gain boosting based on reactive feedback applied to common-emitter devices follows, and a low-noise amplifier demonstrates 23.8 dB power gain, 130 - 165 GHz bandwidth and 5 dB noise figure at 150 GHz, a record value which is found in literature only in works that operate with more advanced technology nodes. Phase shifters, needed to perform a coherent summation of the signals at different antenna elements, are investigated in their passive implementation both for fine and coarse phase shift control. Stand-alone structures are realized together with an on-chip TRL calibration kit to validate the concepts. Finally, a front-end module comprising a LNA and a passive phase shifter is described. Phase shifting elements are interleaved with gain-boosted active stages to maximize the receiver’s dynamic range. Experimental results show an average gain of 20 dB and a phase resolution of 7° over the full 0 - 360° phase shifting range. The average noise figure is 7 dB, the best to the authors’ knowledge in similar works to date. With an OP1dB of -2dBm and a DC power consumption of 80mW from a 2V supply, measurement results prove advances in performance with respect to previous works, especially in terms of power efficiency, particularly critical in large arrays. The activities were carried out at the Analog Integrated Circuits (AIC) Laboratory of University of Pavia, and received funding from the Commission of the European Union within the H2020 DRAGON project (Grant Agreement No. 955699) and KDT SHIFT project (Grant Agreement No. 1010962). The definition of system requirements wascarried out in collaboration with the group of Huawei Milan, Italy.