Phase noise reduction in RF CMOS VCO's via capacitive filtering

In English This paper presents the experimental results of two different techniques, the
already known inductive degeneration technique and the new capacitive filtering
technique, for reducing the phase noise in RF CMOS VCO's. The techniques are
applied to two distinct VCO designs, showing that the largest phase noise reduction
(up to 7 dB at 3 MHz offset frequency from the carrier) is achieved via inductive
degeneration. Capacitive filtering, however, also substantially reduces the phase
noise, and may therefore become a valid alternative to inductive degeneration, as
discrete capacitors are of more common use than discrete inductors.