使用0.18-μm CMOS製程之蕭特基二極體與無失真微波被動元件設計60-GHz雙轉頻收發機

Abstract

Recently, most 60-GHz transceivers have been demonstrated using advanced CMOS technologies, such as 90 nm, 65 nm and 45 nm. Low noise amplifier (LNA) and power amplifiers (PA) are the key components in resisting the high 60-GHz path loss caused by oxygen attenuation. Limited by the maximum breakdown voltage and minimum noise figure (NFmin) of CMOS devices, 60-GHz CMOS PAs possess small output power and low power-added efficiency (PAE) while 60-GHz CMOS LNAs have no significant improvement in noise figure even with advanced CMOS technologies. This impairs the development of 60-GHz portable equipment. Compared with CMOS technologies, III-V GaAs-based technologies inherently have a superior noise figure with low DC power consumption and large linear output power with high PAE. Thus, this dissertation proposes an alternative approach to a 60-GHz transceiver, in which the LNA/PA are realized using III-V GaAs-based technology and the other circuits of the 60-GHz front-end are fully implemented using low-cost 0.18-μm CMOS foundry technology. The latter has been successfully demonstrated in our work. The low photolithography cost of the 0.18-μm CMOS process allows iterations to solve the problem of inaccurate device modeling, greatly reducing the costs in the R&D phase. Two key components of the 60-GHz 0.18-μm CMOS dual-conversion transceiver are the introductions of a Schottky diode and a distortionless microwave passive component. The Schottky diode, with its high cut-off frequency, promotes the speed of the 0.18-μm CMOS technology beyond fT of an MOS device, while its low turn-on voltage alleviates the difficulty of millimeter-wave LO generation with 0.18-μm CMOS technology. Distortionless transmission theory for miniaturization is developed in the passive component design. Size shrinkage by the effective dielectric constant is still preserved even if the attenuation constant coexists. When implementing a microwave component directly on silicon substrate, high silicon dielectric constant is of great benefit in size shrinkage. Although the effect of lossy silicon substrate is induced, step-impedance and lump-distributed techniques are employed in this work to effectively reduce transmission-line length for small silicon-substrate and metal loss. Here, a phase-inverter rat-race coupler with excellent amplitude/phase balance is the main object of study. Incorporating the step-impedance technique with the Chebyshev response, compact size and wide bandwidth can be simultaneously attained in the phase-inverter rat-race coupler. Finally, different kinds of high-speed frequency dividers, such as super-dynamic and regenerative structures, are introduced and discussed.