Techniques for improving CMOS VCO performance

In this paper, we review some of the well known techniques for improving the performance of CMOS tail current bias LC VCO, such as the phase noise and the tuning range. Based on the better understanding on VCO phase noise mechanism and tuning range limitations, this has lead to newly developed techniques such as noise cancellation VCO and resistively tuned variable inductor, which help improving the VCO performance. The former technique achieves FOM of -186 dBc/Hz while the latter leads to wide tuning range VCO of 56% suitable for tuner application.