Cross-coupled voltage controlled oscillator with improved phase noise performance

Abstract

A cross-coupled voltage controlled oscillator having reduced phase noise. A pair of bipolar transistors having common emitter connections are coupled to reduce that oscillation frequency which is determined from a tuning circuit connected across the collectors of transistors. First and second varactor diodes provide analog tuning of the circuit, and a digitally controlled capacitor provides for a selection of a band of frequencies to be tuned by the varactor diodes. A current source provides the current to the emitter connections of the bipolar transistors. Second harmonic signals generated at the emitter of the transistors are significantly suppressed by a tuned filtered trap connected to the common emitter connections. By reducing the second harmonic signals, the phase noise or the voltage controlled oscillator can be significantly improved.

Dependencies are inferred from the claim text.