Design and Analysis of a 90 nm mm-Wave Oscillator Using Inductive-Division LC Tank

A 60 GHz voltage-controlled oscillator with an inductive division LC tank has been designed in 90 nm CMOS. The analysis of the oscillator shows that the presence of higher harmonics, the capacitance nonlinearity and the very high K _VCO are critical for the phase noise performance of oscillators. Therefore, a pseudo-differential amplifier is employed in this design because of its high linearity. Furthermore, the proposed inductive division reduces the phase noise by increasing the signal amplitude across the varactor, without affecting the operation mode of the cross-coupled pair transistors. It also helps to increase the tuning range by isolating the varactor from the parasitic capacitances of the transistors and interconnects. The mm-wave oscillator is fabricated in a 90 nm CMOS technology. Under 0.7 V supply, the oscillator achieves a tuning range from 53.2 GHz to 58.4 GHz, consuming 8.1 mW. At 58.4 GHz, the phase noise is -91 dBc/Hz at 1 MHz offset. Under 0.43 V supply, the oscillator achieves a tuning range from 58.8 to 61.7 GHz. At 61.7 GHz, the phase noise is -90 dBc/Hz @1& MHz offset with a power consumption of only 1.2 mW.