A 1.8 GHz CMOS voltage-controlled oscillator

This paper describes the factors that limit the tuning range of monolithic LC voltage-controlled oscillators (VCOs), especially at low supply voltages, and introduces circuit techniques that alleviate this problem. Incorporating such techniques, a 1.8 GHz CMOS oscillator achieves a tuning range of 120 MHz with a relatively constant gain while exhibiting a phase noise of -100 dBc/Hz at 500 kHz offset. The actual implementation is a quadrature generator consisting of two coupled oscillators. Since the two oscillators are identical, only one is considered here.