Transformer-based dual-mode voltage-controlled oscillators

In this brief, we propose to use a transformer-based resonator to build a dual-mode oscillator, e.g., a system capable of oscillating at two different frequencies without recurring to switched inductors, switched capacitors, or varactors. The behavior of the resonator configured as a one-port and a two-port network is studied analytically, and the dependence of the quality factor on the design parameters is thoroughly explored. These results, combined with the use of traditional frequency tuning techniques, are applied to the design of a wide-band voltage-controlled oscillator (VCO) that covers the frequency range 3.6–7.8 GHz. The performance of the designed VCO, implemented in a digital 0.13-um CMOS technology, has been studied by transistor-level and 2.5D electromagnetic simulation (Agilent Momentum). A typical phase noise performance at 1-MHz offset of -104 dBc Hz has been predicted, while the power consumption ranges from 1 to 8 mW, depending on the VCO configuration.