A Sub-1-V 4-GHz CMOS VCO and a 12.5-GHz oscillator for low-voltage and high-frequency applications

This paper presents the design and experimental measurements of four CMOS LC-based oscillators. The design methodologies of two different topologies and approaches for their optimization are presented. The first topology is optimized for low voltage operation in a 0.25-μm process, which is demonstrated by a finest prototype, requiring only a 0.85-V power supply and reaching a maximum frequency of 4 GHz. A second circuit, using the same architecture in a 0.35-μm process, oscillates at 5 GHz and operates from a 1.5-V power supply, while maintaining reasonable phase noise (-87.3 dBc/Hz @ 100 kHz offset). Finally, the third and fourth oscillators, based on a PMOS-NMOS complementary differential structure, were optimized for high frequency, reaching maximum oscillating frequencies of 10.5 GHz and 12.5 GHz, in a 0.35-μm process. The oscillators make use of on-chip components only, allowing for simple and robust integration