VOLTAGE CONTROLLED OSCILLATOR HAVING A PHASE NOISE REDUCTION DEVICE

摘要

Differential voltage controlled oscillators are provided including a differential oscillator core, a first linear capacitor, a second linear capacitor, a first phase noise reduction device, and a second phase noise reduction device. The differential oscillator core has a first output that is capacitively coupled to a first differential input thereof by a first semiconductor junction having a first non-linear capacitance, and a second output that is capacitively coupled to a second differential input thereof by a second semiconductor junction having a second non-linear capacitance. The first linear capacitor is electrically cross-coupled from the first differential input to the second output, while the second linear capacitor electrically cross-coupled from the second differential input to the first output. The first phase noise reduction device has a first non-linear capacitance characteristic, and is electrically cross-coupled from the first differential input to the second output. The second phase noise reduction device has a second non-linear capacitance characteristic, and is electrically cross-coupled from the second differential input to the first output. By using the first and second phase noise reduction devices to add non-linear junction capacitance to each side of the differential structure, non-linear junction capacitances of the first and second semiconductor junctions are effectively canceled out to reduce the phase noise of the oscillators in which they are used.