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Due to the benefits of Schottky diodes, 0.18-μm CMOS technology is being promoted for millimeter wave applications. In this paper, 60-GHz dual-conversion down-/up-converters using Schottky diodes are realized by using 0.18-μm foundry CMOS technology. A CoSi2-Si Schottky diode, fabricated on a lower doped N-well by blocking the threshold voltage adjustment implant, has a lower reverse leakage current and a better ideality factor. Thus, it is ideal for the 60-GHz sub-harmonic mixer design. Two new types of Schottky-diode mixers, a down-conversion sub-harmonic mixer with a dual-band lump-distributed phase-inverter rat-race coupler and an up-conversion sub-harmonic mixer with a trifilar transformer, are realized and employed at the high-frequency conversion stage of the dual-conversion architecture to achieve small size and broadband isolations. The silicon-based Schottky diode with a low turn-on voltage offers great advantage in LO pumping power, especially for an antiparallel diode pair structure. In our Schottky-diode sub-harmonic mixers, the required LO power is only 1 dBm. The dual-conversion down-converter achieves 5-dB conversion gain and 19 dB noise figure under Vdd=2.5 V and Idd=22 mA, and the dual-conversion up-converter, with Vdd=2.5 V and Idd=26 mA, attains greater than 40-dB sideband rejection and -1 dB conversion gain over the whole 60-GHz bandwidth.
Microwave Theory and Techniques, IEEE Transactions on (Volume:60 , Issue: 6 )
Date of Publication: June 2012