A Quadrature Frequency Generation Chain for Direct-conversion Phased-array 5G Transceivers

Abstract: The 5th generation (5G) has recently specified a new spectrum range, FR2- 5G New Radio (5G-NR), to provide higher spectral efficiency and channel capacity for ubiquitous cellular connectivity where the user ends can be in various types such as picocell stations, sensor nodes, cloud servers, hand-held devices, and so on. Due to the advantage of phased array antennas in performing beam-forming, and improving SNR at higher spectra, multi-antenna systems have gained an inevitable role in developing such radios. However, attributed to their multi-path feature, their corresponding silicon solutions are often complex, power-hungry, and bulky which all together limit their practicality for low power and compact solutions. This introduces an additional hurdle to the RFIC units of 5G radios which already is challenged by strict cellular requirements. During the recent years, the developing short channel silicon-on-insulator (SOI) CMOS technology has provided distinguished characteristics for CMOS transistors. Thanks to the smaller scale and the isolated substrate, the CMOS transistors provide a considerable improvement in power efficiency. Also, they provide a highly controllable characteristic promising novel architectures and circuits. All the merits considered, short channel SOI technology has taken an indisputable role in developing advanced RFIC units. This thesis benefits from Global Foundries’ 22-nm fully depleted silicon-on-insulator (FD-SOI) process, and presents a power-efficient LO phase shifting RFIC unit for direct conversion phased array transceivers. The proposed solution covers the sub- 30 GHz bands including n257, n258, and n261 (24.25 GHz- 29.5 GHz). The chain supports the required frequency range with a single VCO by providing a 31.5% tuning range. The VCO occupies 0.025 mm2, and consumes 5.1 mW on average and its phase noise at 1 MHz offset varies between -95 dBc/Hz to -98 dBc/Hz. Accordingly, its FOM and FOMt at 1 MHz offset is -177.8 dBc/Hz and -187.7 dBc/Hz respectively. Furthermore, the chain provides a tunable quadrature LO generation that consumes 15.8 mW and provides at least 40 dBc image rejection ratio (IRR) over the targeted bandwidth. As the last stage, for accomplishing the array steering, a low power active phase shifting unit is proposed. The proposed phase shifter occupies 0.01 mm2, and provides 93-110 degree phase-shifting for each of the quadrants within the specified bandwidth. The phase-shifting unit and its following output buffer consume 2.8 mW and 2.7 mW respectively For each quadrature paths.