ISSCC 2004 / SESSION 9 / GBIT - TRANSCEIVERS / 9 . 7 9 . 7 A 20 GHz VCO with 5 GHz Tuning Range in 0 . 25 μ m SiGe

A low phase-noise wide tuning range VCO is a critical building block in high-performance serial interface circuits. A negativeresistance cell that has a small effective parasitic capacitance combined with high-quality LC tanks are crucial for high quality VCOs. There have been several efforts to reduce the parasitic capacitance of the basic Armstrong structure [1,2] to improve the VCO performance, but these structures require an integrated transformer that is non-trivial to design, especially at high frequencies. This paper presents a capacitive emitter-degenerated differential negative-resistance cell that has a very small effective parasitic capacitance, with the result that it is capable of a large tuning range with low phase noise and small power consumption. The 20GHz VCO design is implemented in a 0.25μm SiGe BiCMOS, and shows a wide tuning range, 5GHz, with small power consumption and low phase noise.