Patent ID: 7728687

Claim:
An oscillation circuit, comprising: (a) an LC oscillator including an inductor and a variable capacitor electrically coupled together, wherein the inductor and the variable capacitor are configured such that if the variable capacitor charges/discharges, then at least a portion of the charge/discharge electric current of the variable capacitor flows through the inductor; (b) first and second differentially-coupled transistors (i) electrically coupled to the LC oscillator and (ii) configured to provide negative resistance to the LC oscillator; (c) a first current-injecting circuit (F) electrically coupled to the first differentially-coupled transistor and (ii) configured to inject a first additional electric current into the first differentially-coupled transistor so as to cause the first differentially-coupled transistor to create a first additional negative resistance to the LC oscillator, wherein the first differentially-coupled transistor is configured to receive a first original electric current other than the first additional electric current; and (d) an injection current adjusting circuit (i) electrically coupled to the LC oscillator and the first current-injecting circuit, and (ii) configured to cause the first current-injecting circuit to inject the first additional electric current into the first differentially-coupled transistor in response to a frequency change of the LC oscillator, wherein the first additional electric current is inversely proportional to the frequency change.