Patent ID: 8902009

Claim:
A digitally controlled oscillator (DCO) configured to generate a radio frequency (RF) output signal, the DCO comprising: an inductor-capacitor (LC) tank circuit having a loss component, the LC tank configured to generate an output frequency of the RF output signal; an impedance transformer circuit configured to transform a positive impedance associated with the loss component into a negative impedance; and a tuning circuit configured to tune the output frequency of the RF output signal, wherein the impedance transformer circuit comprises a first transistor, a second transistor cross-coupled with the first transistor, a third transistor, and a fourth transistor cross-coupled with the third transistor, wherein the third transistor and the fourth transistor are connected in parallel with the first transistor and the second transistor, wherein a gate of the first transistor is connected to a drain of the second transistor, a gate of the second transistor is connected to a drain of the first transistor, the drain of the first transistor and the drain of the second transistor are connected to the LC tank circuit, and a source of the first transistor and a source of the second transistor are connected to the tuning circuit, and wherein the source of the first transistor is connected, via the tuning circuit, to a first current source configured to bias the first transistor, and wherein the source of the second transistor is connected, via the tuning circuit, to a second current source configured to bias the second transistor.