A wide-tuning range transfomer-based RF CMOS oscillator

This paper presents a method of producing a Voltage Controlled Oscillator (VCO) with a wide enough tuning range, such that the correct centre frequency can be ensured. This is achieved without compromising the power consumption of the circuit. The work is novel in that a transformer is preferred to an inductor to help maximize this tuning range. The design was fabricated in a CMOS 0.18µm technology, and has a frequency tuning range between 2.35 and 2.95GHz, drawing 20mA from a 1.8V supply. A staggered-tuning range was employed to minimize the effect of noise on the analog control voltage, so the control process is a dual one, with both analog and digital controls. The oscillator produces quadrature outputs which are essential for many transceiver systems.