| 摘要 |
Circuits and methods for tuning voltage-controlled oscillators. A control voltage is applied through an isolation resistor to a varactor. The varactor capacitance is AC coupled through a second capacitance. The control voltage may be analog or digital. In a specific embodiment, multiple tuning diodes, and both analog and digital control voltages are used. The isolation resistor is outside the VCO tank circuit for low phase noise, excessive Kvco is reduced, and the control and output voltages of the oscillator may swing over the entire supply range. The varactor capacitance may be junction, MOS, or other type of varactor. |
