Hybrid voltage-controlled oscillator with low phase noise and large frequency tuning range

Abstract

A transformer LC oscillator utilizing the low phase noise of spiral LC oscillator and the large frequency tuning range of active inductors is proposed to yield both a large frequency range and low phase noise. The oscillator is a passive transformer LC oscillator with the primary winding of the transformer connected to the oscillating nodes of the oscillator and the secondary winding loaded with an active inductor. The contribution of the noise of the active inductor is minimized by adjusting the coupling of the transformer such that the overall phase noise of the oscillator is much lower as compared with that of corresponding active inductor oscillators while the frequency tuning range of the oscillator is much larger than that of passive transformer oscillators. The VCO has been designed in an IBM 130 nm 1.2V CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3 device models. For purpose of comparison, an active inductor LC oscillator and a spiral inductor LC oscillator have also been designed and analyzed. The phase noise of the active inductor, spiral transformer, and hybrid oscillators at 1 MHz frequency offset from their nominal oscillation frequency is $$-$$-80.18, $$-$$-106.9, and $$-$$-100.5 dBc/Hz, respectively. The power consumption of the spiral inductor, active inductor, and hybrid oscillators is 4.8, 30, and 34.8 mW, respectively.