2.4GHz VCO design and tail current analysis

Abstract

This paper presents an LC-based oscillator structure of a widely used complementary cross-coupled VCO. This structure can be widely used in wireless communication, optical communication and high-speed A/D converter, even more other ISM systems. Here is the specification: the supply voltage is 3.3 volts, central oscillation frequency is 2.4 GHz, the tuning range is 21% or so, the power consumption is low, and the phase noise is low enough to meet the DCS-1800 standard. Two prototypes are designed: one uses PMOS current mirror, the other uses NMOS current mirror. Then a comparison is made between the two, and a conclusion is reached on how the tail current affects the whole performance of VCO.