A switched-transformer, 76% tuning-range VCO in 90nm CMOS

This paper presents a prototype of multi-mode, multi-band CMOS VCO with a switched-transformer resonator, designed and fabricated in 90nm CMOS process. By combining the characteristics of switched-capacitors VCOs, transformer-based VCOs and switched-inductor VCOs, five VCO operation modes were realized, achieving a measured 76% tuning range spanning the bands 2.32-3.36 GHz, 3.45-4.55 GHz, and 4.89-5.83 GHz. The VCO draws a current ranging from 11.0mA to 23.4 mA from a 1.8 V supply, with a phase noise of -130.2 dBc/Hz (-118.3 dBc/Hz) at 1 MHz offset from the 2.32 GHz (5.83 GHz) carrier. The power-frequency-tuning-normalized figure-of-merit (PFTN-FoM) varies from -9.5 dB to 13.2 dB.